Final Photos and Final Testing, stereo 6005 SE DC amp from 2021

drlowmu

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First order of business , a public apology to Yogibear.

There was a mistake, in that I initiated a written private email apology to Yogibear ( Samir ) on 2-09-2022, with a CC to Hari Iyer. This apology was totally my own unsolicited idea. He deserved it.

Somehow it seems, Yogibear had forgotten or was fully unaware of my apology.

He requested yesterday that I make it public, and I have no problem doing so.


APOLOGY 2-9-22.JPG
 
03-01-2022 ................ PHOTO PROGRESS REPORT ............99% FINISHED AMPLIFIER BUILD ..........


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I have gotten requests to show the top side. This amp is finished - breaking in now, chassis #2.

Chassis #1, my own amp, is out for testing, and it takes time.


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Last edited by a moderator:
Please keep posts specifically in this thread technical or design relevant. This is a DIY thread and the OP has the right to post his continuing design and others to have technical comments questions/discussions/reviews etc.

ANY post getting personal, accusatory or deemed as offensive and irrelevant towards anyone will be deleted and the member banned by the mods. This includes any questioning of this since it is not just ridiculous and tiring but childish.
 
TESTING a DIY amplifier......... after it's Completion 3-3-2022

Testing means different things, to different people .

Many people would like to put a finished amp " on the bench ", feed it test signals, and determine how the amp "looks" on oscilloscope traces. Nothing wrong with that ! Good idea.

On a simple amplifier such as what I build, two tube stages, directly coupled, I almost never do this.

I assume the amp I build is working well. I prefer to use a single digital multimeter to simply test the amplifier. ( Fluke 8060A, a nice one ).

The very first thing done is to slowly and carefully variac the amplifier UP in voltage, and continuously check all the various key voltage locations in the circuit, to ESTIMATE if they are tracking each other. I will typically test the key circuit locations, first at 35 % power, and about 75% power. Once full power is reached, all these key circuit locations should measure within about 5% or less, of the schematic's theoretical design voltages.

The 100% powered measured voltages usually measure within 2% to the theoretical design. I allow the new amp to idle for an hour, come to full operating temperature, and recheck all key voltages....... one more time.

My personal idea of testing an amplifier, is to listen to it on music playback, and determine HOW well the amplifier plays back various music instruments.

I feed the amplifier as clean and consistent of a music signal as possible, and will listen to music selections from about a ( uniform ) dozen differing CD sources. The question is always the same : How do these music instruments sound to me ? Does the cello sound like a real cello, if it was well recorded?? How are the various instruments' playback comparing on my speakers ( vintage ALTEC Voice of the Theater A7-8s ) - versus every other amp I have built, powered, and tested ?

For consistency, over the last 8 years or so, I always use the same source equipment and test material. Pioneer's BPD-09FD bluray player, a 31 pound top-of-their line model. I only use only ONE interconnect cable between this source and the amplifier, to minimize music signal losses.

That is right, no signal attenuator ( passive ) is used, only because it requires a second set or RCA jack connections ( more unwanted losses ) and an entire second signal interconnect cable ( losses in the cable ). There are internal losses in every passive attenuator also, switches, wiring, solder joints, contacts, parts, etc . ) !!

So every amp tested gets a " full bore " input music signal !! In many instances ... it is loud. Thank goodness, my amps are usually in the one to three Watt output range. :) The ALTEC speaker is typically unstressed. No next-door neighbors to worry about either. The amp itself however, on some CDs, can be over-driven, and this has to be mentally taken into account.

The standard CDs used for testing are very varied. Instruments I pay particular attention to are jazz and grand piano , human voice, complex music orchestrations, and a drum kit CD.

My personal favorite test CD is entitled " Steve Clarke, Solo Drums ", recorded in the UK in 2,000 by Wenlock " WEN020 ". It is multimiked closely, a very large drum kit with eight drums and four cymbals. There is so much information to listen to on this CD, which a good zero-negative-feedback SE DC tube amp design may unravel and lay bare. Steve's first solo lasts 15:21 minutes, and his second solo is 20:56 minutes.

After listening to the instruments and music playback, with a consistent " menu " of a dozen CDs, one can obtain a very good subjective idea, of how any new amp design plays back !!! After about five days of critical listening...one knows !!!

I am pleased to report, that this new STEREO 6005 amp ( about 3 Watts ) is subjectively playing back instruments over 20% better than my previous " high water mark " amplifier design and build. ( A SE DC KT88 design, from 2019. )

The 2021 KT88 stereo amp was no slouch. In 2019 it easily outperformed a pair of deluxe monoblock 2A3 amps ( $ 19.75 K a pair ) with rare top-of-the-line vintage VAIC 2A3 mesh plate tubes in it. ( A 4,000 mile car trip was required, ..... to do that test ).

The new 6005 stereo amp is to be tested further, ( not just on my VOTTs and my equipment and my hearing ).

The now-finished Chassis #1 6005 amp is now located 55 miles from me, in an entirely different ( stellar ) high efficiency audio system. It's evaluation is taking extra time. A report will be forthcoming. This second test will be hopefully photo-documented on HFV and subject of an interesting follow-up post.

Amps available for comparison at this new test site are a highly-tweaked deluxe stereo Japanese 300 B amplifier and a pair of monoblock 845 German Thoress amplifiers. ( a 3 watt amp, 8 Watt amp, and 20 Watt amps, on extremely rare 105 dB efficient front-horn-loaded ALTEC speakers ). All really great stuff,........ IMHO.

Thanks for visiting here. Thank you Moderators for allowing me to report !! DIY can sure be lots of fun.

Jeff
 
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The Last “ One Percent ” …............ Part 1, of 2 Parts …..............03-05-22


In the heading of the second post of this build thread, on 03-03-22, it was mentioned the 6005 amp / Chassis #2, was 99 percent finished.

This post relates to the last one percent needed,....... to finish that build.

There remained two different tasks :


Task ONE, orientate by ear all the five AC connections, to have synchronized, best sounding AC waveform polarities.

Task TWO, build a bottom-of-the-chassis cover plate which will also act as an Isolation Platform.

This post represents TASK ONE, ( the five different AC orientations, their synchronization and optimizing. )

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Every tube audio amplifier, manufactured or DIY, “ ideally” should address the AC polarity feeds of these following five circuitry areas :

1) AC power cord input to the amplifier. If ( hopefully ) using a grounded 3 wire power cord, are the “ hot and neutral ” connections optimized , AC polarity wise, so the amp sounds it best on music playback ???


THE ABOVE, may be considered as a gross and minimal first area to address.

THE BELOW, addresses the INTERNAL optimizations of the amplifier, AC polarity – wise:



2) The Input tube's AC filament feed orientation.

3) The Main Power Transformer's High Voltage Secondary winding.

4) The Rectifier tubes' AC filament wiring.

5) The Output tube's AC filament wiring


- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - – - - - - -

There are two methods I can think of to optimize AC polarity. One can look at waveform directions on a scope, and get all the above five AC waveforms to move in a similar direction, simultaneously.

One AC polarity should not 180 degrees “ buck or skew ” any of the others, which is audible in a high performance SE tube amplifier.

I don't trust this first approach, by itself. For example, what if the waveforms are all moving simultaneously, but exactly 180 degrees out of what sounds ideal !!!

I build DIY SE amps to try to make them better in sound, from what ever I can purchase manufactured. The “ sound ” is the end criteria ( along with reliability ). So what about determining optimum AC polarity a second way. Why not determine precisely how each AC - fed circuit sounds it's best, in its 180 degree hook up orientation, when operating in the amplifier???

This approach only takes a soldering iron, and two decent clip lead wires ( to reverse phase ) and music to play ( consistently as a source ). This seems most fool proof to me, and it is precisely how I have been optimizing AC in SE DC amp builds since mid 2019. Count me...... “ all in ”.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

To prepare a newly built amplifier, for by-ear AC orientation, it is best to break it in first on music playback for a minimum of 75 to 100 hours. I did a “ silent ” break in of the finished Chassis #2 over the past week or two.

( From previous experiences, the Main Hammond 159ZA power supply chokes, the E.H. 5U4GBs, and the RW-20 R-Core Output Transformer windings all require at least 75 hours of break in ).

A vintage modest Magnavox CD player, which has a repeat function, continuously played full bore volume into the new Chassis #2 amp, with a low-cut CD music source. Instead of attaching loudspeakers, I placed 15 Ohm 5 Watt power resistors, across both channel's Cardas Speaker Binding posts. This properly loads the music-driven Softone RW-20 output transformers. This set up can run day and night silently, even while I am asleep in the evening. Wonderful. Many off-and-on cycles are interspersed, with time to allow the unit to cool down . By this past Friday evening, 03-04-2022, the amp was broken in enough to evaluate critically, those five above-mentioned AC orientations by ear.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - – - - - - -

The test-set-up has been previously discussed. Pioneer's older top-of-the-line BPD-09FD Blu Ray player. A single set of RCA interconnects, directly feeding the amp under test, with the Player going into the amp with a full-bore music signal. That is right. No attenuator, or a second set of RCA interconnects, with various connection and cable and parts degrades, to get in the way of feeding the best possible / repeatable signal into the amp for critical music evaluation. KISS. It plays back loud, but the ALTEC VOTTS are not stressed with low Watt amps. I have no adjoining neighbors to worry about....... loud-sound-disturbing-wise. Good.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

As a much needed complete mental change-of-pace, I decided to NOT use “ Steve Clarke, Solo Drums ” as the AC orientation music source. Instead, I chose Mark Knopfler / Dire Straits / Brothers In Arms, by Warner Brothers 114734 D, circa 1985. Boutique Hi Fi stores in the USA use this CD often. They love to demonstrate Magneplaners, and to sell costly kilowatt KRELL power amps to the public. LOL.

OK, here we go :

AC TEST ONE...... the POWER CORD orientation :

The new 6005 amp is totally unknown as to AC optimization here, so one has to make a gross guess, as to what 180 degree AC feed orientation sounds best. I used a cheap ( under a dollar ) 3 into 2 AC adapter, with its wider ground prong filed to be narrower. It could be inserted into my wall socket, either polarity, to obtain 180 degree changes. I went back and forth about four or five times, until I was satisfied, that one AC plug-in orientation sounded the best overall. No, I certainly was not looking for lowest hum with a DMM. I wanted to discover what orientation overall sounded the best to me on music. For the rest of my testing, this polarity stayed CONSTANT.


AC TEST TWO - the INPUT tube's AC filament excitation :

The Input tube is the most important stage of the amp to optimize. Two reasons, it has the most gain ( in a DC two stage amp ) and any fidelity / resolution loss in the first stage of music signal amplification, is impossible to make up in later stages .

Notice from prior post photos, all AC filament wiring is twisted gray and white colored ( 16 AWG m22759/11 ) wiring. I carefully solder the same colored wires to the same tube socket pin numbers, for each channel. All I did was unsolder the gray and white wire's connections, to the filament transformer's leads, and use two custom 7 inch long M22759/11/14 AWG clip lead wires, with pure copper alligator clips, to swap the AC feed by 180 degrees.

Good news, “ So Far Away ”, Cut #1, played better, sounded better, right from the start. It played louder and with better colors and harmonics. Resolder the gray and white wires to the new and better AC orientation, and go on to the next area to analyze. Happier. A good start.

AC TEST THREE - the Main Power Transformer's SECONDARY High Voltage WINDING :

This is a large custom Shilchar 320 VA R-core Power Transformer. Unsolder the two high voltage secondary leads and clip lead re-orientate them, 180 degrees AC flipped.

Be very careful here, with lead dress and clip lead connections, as we are dealing with highly lethal 800 Volts of AC across this winding!!!!! Check twice before power up. Have your wits about you.

From the very first note played on Cut #2, “ Money for Nothing ” there was an easy to hear improvement. The amp played the music louder, more dynamic, and slightly more defined. There is a fabulous early guitar solo, stage left, and it was better now - than all the prior AC steps.

But the entire presentation was not quite right, not quite believable yet.. The guitar solo seemed to lack “ drive ” of the bottom portion of the guitar's body,... drive into the recorded space, and into my room. The high end of the guitar still seemed to predominate ever so slightly . The opening bass chords on Cut #1, “ So Far Away”, however were much improved...we were getting there.

Resolder High Voltage Secondary leads to their new 180 degree different orientation, and go on.

At this point in time, I had the following thought : “ I wish the nice audiophile Hong Kong client who will get this Chassis #2 amp, and Mr. Hari Iyer, were sitting in the room with me, to be able to hear and appreciate these subtle, cumulative changes. It would have been a great listening experience - for them both. All unmistakable.

AC TEST FOUR, the TUBE RECTIFIER FILAMENT wiring :

Same deal, unsolder the original two leads, clip lead and reverse polarity these two leads. This is a 5 VCT at 6 Ampere power transformer, custom Shilchar R-core, to power dual 5U4GB rectifier tube filaments.

Ohh my Goodness !!!! From the very first notes of “ Money For Nothing “, Cut #2 , the amp sounded appreciably better again !!! It played louder, with more dynamics, noticeably more energy into my listening room, in the X,Y, and Z axis. The opening bass notes in “ So Far Away ”, Cut #1, sounded AOK for the first time ( I love the ALTEC 515B 15 inch woofers ) , and totally believable to me. Guitar plucking that was in the background, and previously “ lost in the mix ”, was now being heard as distinct , on time, and defined. Resolution of subtle background accompanying voices, was now more distinct and better placed in all axis. The entire audio system played bigger, with more dynamic contrasting in the room.

Hey dear Forum friends, this is getting wild. There is a 50-50 chance that an AC connection is in best sounding phase. Now, we are at 80-20, after four of five AC orientation swaps !!

The wild guitar solo in Cut #2 showed signs for the first time, of proper harmonics, and energy, including finally, the lower body of the instrument. It still wasn't quite as good as I heard it with amp/chassis #1, but it really was getting there.

By this time, the listening session was long, and getting late in the evening. I thought of retiring for the night. But the unknown outcome of “ What would happen ” at TEST # 5, the FINAL AC orientation test, would have never allowed me to go to sleep. Any audiophile and DIY amp builder, worth their salt, would continue.

OK. OK. I soldered in the tube rectifier filaments to its new ( reversed and better sounding ) AC phase, and went on to unsolder and swap the last connection, the Output tubes AC powered filaments. Clip leaded them in 180 degrees opposite.

AC TEST FIVE, the OUTPUT TUBES' AC filament excitation.

Ohh my goodness again, from the opening note, the system played from the bottom up, cleaner, louder, and with more dynamics. Music resolution, definition, harmonic structuring, was “ off the scale .” The speakers disappeared in my living room, and the power and dynamic contrasting of the music was wonderful to experience.

Realize, this amp has a total of 12 Ohms DCR to the Finals tubes for B+ inductive filtering, and dual rectifier tubes, GTO capacitors, and much use of 12 AWG Mil Spec wiring. These corrected / optimized AC orientations, in all five circuit locations, allowed me to achieve a great and permanent music listening performance improvement, to be enjoyed on my nice friend's Beauhorn Virtuosos.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- --- - - - - - - - - - - - - - - - - - -

Imagine starting this AC test procedure with a 50 -50 chance of some of the AC connections being ideal, and discovering that it was a 100% to 0%..... actual result. All were in need of swapping. ( Note : I am not sure of the very first test result ).

This overall amplifier improvement, with my type of circuit, and power supply, was substantial. F.M. Hari Iyer, I suggest for you to do your KT88 DC amps...... this same precise way . :)

At no time during this Chassis #2 testing, did I have the Softone RW-20 steel transformer covers mounted over the output transformers. It was an audible degrade, easily detected on my system. At no time during this testing, did I allow the two speaker lead polarities touch each other, in the distance between the new 6005 amp, and the speaker crossovers. They were suspended in mid-air. ( No polarity touch, no polarity twisting, eliminates loss of high end music information ).

One point I would like to make is, no one would get this performance, from this type of SE DC amp, unless they did this “ last 1 % ”, …....to finish the build properly !!

Another point. No manufacturer I am aware of, does all of this type of optimization, and I have never seen or heard a discussion among my fellow DIYer amp builders over the decades, about this procedure. Of course, we must all realize, I have not on-line researched this specifically, and I am certainly not privy to all that happens in tube amp builds on Planet Earth. :)

My knowledge of all of this comes directly from my mid 2019 KT88 SE DC amp build, where I was confronted with the use of multiple power transformers. I am self - taught. Any sincere questions, fire away !!

A++ to anyone who has read all of this post.

I hope, in future years, and for a few future DIY tube amp builders, that this approach does not get lost .

Jeff
 
Last edited:
The Last “ One Percent ” …............ Part 1, of 2 Parts …..............03-05-22


In the heading of the second post of this build thread, on 03-03-22, it was mentioned the 6005 amp / Chassis #2, was 99 percent finished.

This post relates to the last one percent needed,....... to finish that build.

There remained two different tasks :


Task ONE, orientate by ear all the five AC connections, to have synchronized, best sounding AC waveform polarities.

Task TWO, build a bottom-of-the-chassis cover plate which will also act as an Isolation Platform.

This post represents TASK ONE, ( the five different AC orientations, their synchronization and optimizing. )

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Every tube audio amplifier, manufactured or DIY, “ ideally” should address the AC polarity feeds of these following five circuitry areas :

1) AC power cord input to the amplifier. If ( hopefully ) using a grounded 3 wire power cord, are the “ hot and neutral ” connections optimized , AC polarity wise, so the amp sounds it best on music playback ???


THE ABOVE, may be considered as a gross and minimal first area to address.

THE BELOW, addresses the INTERNAL optimizations of the amplifier, AC polarity – wise:



2) The Input tube's AC filament feed orientation.

3) The Main Power Transformer's High Voltage Secondary winding.

4) The Rectifier tubes' AC filament wiring.

5) The Output tube's AC filament wiring


- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - – - - - - -

There are two methods I can think of to optimize AC polarity. One can look at waveform directions on a scope, and get all the above five AC waveforms to move in a similar direction, simultaneously.

One AC polarity should not 180 degrees “ buck or skew ” any of the others, which is audible in a high performance SE tube amplifier.

I don't trust this first approach, by itself. For example, what if the waveforms are all moving simultaneously, but exactly 180 degrees out of what sounds ideal !!!

I build DIY SE amps to try to make them better in sound, from what ever I can purchase manufactured. The “ sound ” is the end criteria ( along with reliability ). So what about determining optimum AC polarity a second way. Why not determine precisely how each AC - fed circuit sounds it's best, in its 180 degree hook up orientation, when operating in the amplifier???

This approach only takes a soldering iron, and two decent clip lead wires ( to reverse phase ) and music to play ( consistently as a source ). This seems most fool proof to me, and it is precisely how I have been optimizing AC in SE DC amp builds since mid 2019. Count me...... “ all in ”.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

To prepare a newly built amplifier, for by-ear AC orientation, it is best to break it in first on music playback for a minimum of 75 to 100 hours. I did a “ silent ” break in of the finished Chassis #2 over the past week or two.

( From previous experiences, the Main Hammond 159ZA power supply chokes, the E.H. 5U4GBs, and the RW-20 R-Core Output Transformer windings all require at least 75 hours of break in ).

A vintage modest Magnavox CD player, which has a repeat function, continuously played full bore volume into the new Chassis #2 amp, with a low-cut CD music source. Instead of attaching loudspeakers, I placed 15 Ohm 5 Watt power resistors, across both channel's Cardas Speaker Binding posts. This properly loads the music-driven Softone RW-20 output transformers. This set up can run day and night silently, even while I am asleep in the evening. Wonderful. Many off-and-on cycles are interspersed, with time to allow the unit to cool down . By this past Friday evening, 03-04-2022, the amp was broken in enough to evaluate critically, those five above-mentioned AC orientations by ear.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - – - - - - -

The test-set-up has been previously discussed. Pioneer's older top-of-the-line BPD-09FD Blu Ray player. A single set of RCA interconnects, directly feeding the amp under test, with the Player going into the amp with a full-bore music signal. That is right. No attenuator, or a second set of RCA interconnects, with various connection and cable and parts degrades, to get in the way of feeding the best possible / repeatable signal into the amp for critical music evaluation. KISS. It plays back loud, but the ALTEC VOTTS are not stressed with low Watt amps. I have no adjoining neighbors to worry about....... loud-sound-disturbing-wise. Good.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

As a much needed complete mental change-of-pace, I decided to NOT use “ Steve Clarke, Solo Drums ” as the AC orientation music source. Instead, I chose Mark Knopfler / Dire Straits / Brothers In Arms, by Warner Brothers 114734 D, circa 1985. Boutique Hi Fi stores in the USA use this CD often. They love to demonstrate Magneplaners, and to sell costly kilowatt KRELL power amps to the public. LOL.

OK, here we go :

AC TEST ONE...... the POWER CORD orientation :

The new 6005 amp is totally unknown as to AC optimization here, so one has to make a gross guess, as to what 180 degree AC feed orientation sounds best. I used a cheap ( under a dollar ) 3 into 2 AC adapter, with its wider ground prong filed to be narrower. It could be inserted into my wall socket, either polarity, to obtain 180 degree changes. I went back and forth about four or five times, until I was satisfied, that one AC plug-in orientation sounded the best overall. No, I certainly was not looking for lowest hum with a DMM. I wanted to discover what orientation overall sounded the best to me on music. For the rest of my testing, this polarity stayed CONSTANT.


AC TEST TWO - the INPUT tube's AC filament excitation :

The Input tube is the most important stage of the amp to optimize. Two reasons, it has the most gain ( in a DC two stage amp ) and any fidelity / resolution loss in the first stage of music signal amplification, is impossible to make up in later stages .

Notice from prior post photos, all AC filament wiring is twisted gray and white colored ( 16 AWG m22759/11 ) wiring. I carefully solder the same colored wires to the same tube socket pin numbers, for each channel. All I did was unsolder the gray and white wire's connections, to the filament transformer's leads, and use two custom 7 inch long M22759/11/14 AWG clip lead wires, with pure copper alligator clips, to swap the AC feed by 180 degrees.

Good news, “ So Far Away ”, Cut #1, played better, sounded better, right from the start. It played louder and with better colors and harmonics. Resolder the gray and white wires to the new and better AC orientation, and go on to the next area to analyze. Happier. A good start.

AC TEST THREE - the Main Power Transformer's SECONDARY High Voltage WINDING :

This is a large custom Shilchar 320 VA R-core Power Transformer. Unsolder the two high voltage secondary leads and clip lead re-orientate them, 180 degrees AC flipped.

Be very careful here, with lead dress and clip lead connections, as we are dealing with highly lethal 800 Volts of AC across this winding!!!!! Check twice before power up. Have your wits about you.

From the very first note played on Cut #2, “ Money for Nothing ” there was an easy to hear improvement. The amp played the music louder, more dynamic, and slightly more defined. There is a fabulous early guitar solo, stage left, and it was better now - than all the prior AC steps.

But the entire presentation was not quite right, not quite believable yet.. The guitar solo seemed to lack “ drive ” of the bottom portion of the guitar's body,... drive into the recorded space, and into my room. The high end of the guitar still seemed to predominate ever so slightly . The opening bass chords on Cut #1, “ So Far Away”, however were much improved...we were getting there.

Resolder High Voltage Secondary leads to their new 180 degree different orientation, and go on.

At this point in time, I had the following thought : “ I wish the nice audiophile Hong Kong client who will get this Chassis #2 amp, and Mr. Hari Iyer, were sitting in the room with me, to be able to hear and appreciate these subtle, cumulative changes. It would have been a great listening experience - for them both. All unmistakable.

AC TEST FOUR, the TUBE RECTIFIER FILAMENT wiring :

Same deal, unsolder the original two leads, clip lead and reverse polarity these two leads. This is a 5 VCT at 6 Ampere power transformer, custom Shilchar R-core, to power dual 5U4GB rectifier tube filaments.

Ohh my Goodness !!!! From the very first notes of “ Money For Nothing “, Cut #2 , the amp sounded appreciably better again !!! It played louder, with more dynamics, noticeably more energy into my listening room, in the X,Y, and Z axis. The opening bass notes in “ So Far Away ”, Cut #1, sounded AOK for the first time ( I love the ALTEC 515B 15 inch woofers ) , and totally believable to me. Guitar plucking that was in the background, and previously “ lost in the mix ”, was now being heard as distinct , on time, and defined. Resolution of subtle background accompanying voices, was now more distinct and better placed in all axis. The entire audio system played bigger, with more dynamic contrasting in the room.

Hey dear Forum friends, this is getting wild. There is a 50-50 chance that an AC connection is in best sounding phase. Now, we are at 80-20, after four of five AC orientation swaps !!

The wild guitar solo in Cut #2 showed signs for the first time, of proper harmonics, and energy, including finally, the lower body of the instrument. It still wasn't quite as good as I heard it with amp/chassis #1, but it really was getting there.

By this time, the listening session was long, and getting late in the evening. I thought of retiring for the night. But the unknown outcome of “ What would happen ” at TEST # 5, the FINAL AC orientation test, would have never allowed me to go to sleep. Any audiophile and DIY amp builder, worth their salt, would continue.

OK. OK. I soldered in the tube rectifier filaments to its new ( reversed and better sounding ) AC phase, and went on to unsolder and swap the last connection, the Output tubes AC powered filaments. Clip leaded them in 180 degrees opposite.

AC TEST FIVE, the OUTPUT TUBES' AC filament excitation.

Ohh my goodness again, from the opening note, the system played from the bottom up, cleaner, louder, and with more dynamics. Music resolution, definition, harmonic structuring, was “ off the scale .” The speakers disappeared in my living room, and the power and dynamic contrasting of the music was wonderful to experience.

Realize, this amp has a total of 12 Ohms DCR to the Finals tubes for B+ inductive filtering, and dual rectifier tubes, GTO capacitors, and much use of 12 AWG Mil Spec wiring. These corrected / optimized AC orientations, in all five circuit locations, allowed me to achieve a great and permanent music listening performance improvement, to be enjoyed on my nice friend's Beauhorn Virtuosos.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- --- - - - - - - - - - - - - - - - - - -

Imagine starting this AC test procedure with a 50 -50 chance of some of the AC connections being ideal, and discovering that it was a 100% to 0%..... actual result. All were in need of swapping. ( Note : I am not sure of the very first test result ).

This overall amplifier improvement, with my type of circuit, and power supply, was substantial. F.M. Hari Iyer, I suggest for you to do your KT88 DC amps...... this same precise way . :)

At no time during this Chassis #2 testing, did I have the Softone RW-20 steel transformer covers mounted over the output transformers. It was an audible degrade, easily detected on my system. At no time during this testing, did I allow the two speaker lead polarities touch each other, in the distance between the new 6005 amp, and the speaker crossovers. They were suspended in mid-air. ( No polarity touch, no polarity twisting, eliminates loss of high end music information ).

One point I would like to make is, no one would get this performance, from this type of SE DC amp, unless they did this “ last 1 % ”, …....to finish the build properly !!

Another point. No manufacturer I am aware of, does all of this type of optimization, and I have never seen or heard a discussion among my fellow DIYer amp builders over the decades, about this procedure. Of course, we must all realize, I have not on-line researched this specifically, and I am certainly not privy to all that happens in tube amp builds on Planet Earth. :)

My knowledge of all of this comes directly from my mid 2019 KT88 SE DC amp build, where I was confronted with the use of multiple power transformers. I am self - taught. Any sincere questions, fire away !!

A++ to anyone who has read all of this post.

I hope, in future years, and for a few future DIY tube amp builders, that this approach does not get lost .

Jeff
Nice work, my friend!
 
The Last “ One Percent ” …............ Part 1, of 2 Parts …..............03-05-22


In the heading of the second post of this build thread, on 03-03-22, it was mentioned the 6005 amp / Chassis #2, was 99 percent finished.

This post relates to the last one percent needed,....... to finish that build.

There remained two different tasks :


Task ONE, orientate by ear all the five AC connections, to have synchronized, best sounding AC waveform polarities.

Task TWO, build a bottom-of-the-chassis cover plate which will also act as an Isolation Platform.

This post represents TASK ONE, ( the five different AC orientations, their synchronization and optimizing. )

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Every tube audio amplifier, manufactured or DIY, “ ideally” should address the AC polarity feeds of these following five circuitry areas :

1) AC power cord input to the amplifier. If ( hopefully ) using a grounded 3 wire power cord, are the “ hot and neutral ” connections optimized , AC polarity wise, so the amp sounds it best on music playback ???


THE ABOVE, may be considered as a gross and minimal first area to address.

THE BELOW, addresses the INTERNAL optimizations of the amplifier, AC polarity – wise:



2) The Input tube's AC filament feed orientation.

3) The Main Power Transformer's High Voltage Secondary winding.

4) The Rectifier tubes' AC filament wiring.

5) The Output tube's AC filament wiring


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There are two methods I can think of to optimize AC polarity. One can look at waveform directions on a scope, and get all the above five AC waveforms to move in a similar direction, simultaneously.

One AC polarity should not 180 degrees “ buck or skew ” any of the others, which is audible in a high performance SE tube amplifier.

I don't trust this first approach, by itself. For example, what if the waveforms are all moving simultaneously, but exactly 180 degrees out of what sounds ideal !!!

I build DIY SE amps to try to make them better in sound, from what ever I can purchase manufactured. The “ sound ” is the end criteria ( along with reliability ). So what about determining optimum AC polarity a second way. Why not determine precisely how each AC - fed circuit sounds it's best, in its 180 degree hook up orientation, when operating in the amplifier???

This approach only takes a soldering iron, and two decent clip lead wires ( to reverse phase ) and music to play ( consistently as a source ). This seems most fool proof to me, and it is precisely how I have been optimizing AC in SE DC amp builds since mid 2019. Count me...... “ all in ”.

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To prepare a newly built amplifier, for by-ear AC orientation, it is best to break it in first on music playback for a minimum of 75 to 100 hours. I did a “ silent ” break in of the finished Chassis #2 over the past week or two.

( From previous experiences, the Main Hammond 159ZA power supply chokes, the E.H. 5U4GBs, and the RW-20 R-Core Output Transformer windings all require at least 75 hours of break in ).

A vintage modest Magnavox CD player, which has a repeat function, continuously played full bore volume into the new Chassis #2 amp, with a low-cut CD music source. Instead of attaching loudspeakers, I placed 15 Ohm 5 Watt power resistors, across both channel's Cardas Speaker Binding posts. This properly loads the music-driven Softone RW-20 output transformers. This set up can run day and night silently, even while I am asleep in the evening. Wonderful. Many off-and-on cycles are interspersed, with time to allow the unit to cool down . By this past Friday evening, 03-04-2022, the amp was broken in enough to evaluate critically, those five above-mentioned AC orientations by ear.

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The test-set-up has been previously discussed. Pioneer's older top-of-the-line BPD-09FD Blu Ray player. A single set of RCA interconnects, directly feeding the amp under test, with the Player going into the amp with a full-bore music signal. That is right. No attenuator, or a second set of RCA interconnects, with various connection and cable and parts degrades, to get in the way of feeding the best possible / repeatable signal into the amp for critical music evaluation. KISS. It plays back loud, but the ALTEC VOTTS are not stressed with low Watt amps. I have no adjoining neighbors to worry about....... loud-sound-disturbing-wise. Good.

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As a much needed complete mental change-of-pace, I decided to NOT use “ Steve Clarke, Solo Drums ” as the AC orientation music source. Instead, I chose Mark Knopfler / Dire Straits / Brothers In Arms, by Warner Brothers 114734 D, circa 1985. Boutique Hi Fi stores in the USA use this CD often. They love to demonstrate Magneplaners, and to sell costly kilowatt KRELL power amps to the public. LOL.

OK, here we go :

AC TEST ONE...... the POWER CORD orientation :

The new 6005 amp is totally unknown as to AC optimization here, so one has to make a gross guess, as to what 180 degree AC feed orientation sounds best. I used a cheap ( under a dollar ) 3 into 2 AC adapter, with its wider ground prong filed to be narrower. It could be inserted into my wall socket, either polarity, to obtain 180 degree changes. I went back and forth about four or five times, until I was satisfied, that one AC plug-in orientation sounded the best overall. No, I certainly was not looking for lowest hum with a DMM. I wanted to discover what orientation overall sounded the best to me on music. For the rest of my testing, this polarity stayed CONSTANT.


AC TEST TWO - the INPUT tube's AC filament excitation :

The Input tube is the most important stage of the amp to optimize. Two reasons, it has the most gain ( in a DC two stage amp ) and any fidelity / resolution loss in the first stage of music signal amplification, is impossible to make up in later stages .

Notice from prior post photos, all AC filament wiring is twisted gray and white colored ( 16 AWG m22759/11 ) wiring. I carefully solder the same colored wires to the same tube socket pin numbers, for each channel. All I did was unsolder the gray and white wire's connections, to the filament transformer's leads, and use two custom 7 inch long M22759/11/14 AWG clip lead wires, with pure copper alligator clips, to swap the AC feed by 180 degrees.

Good news, “ So Far Away ”, Cut #1, played better, sounded better, right from the start. It played louder and with better colors and harmonics. Resolder the gray and white wires to the new and better AC orientation, and go on to the next area to analyze. Happier. A good start.

AC TEST THREE - the Main Power Transformer's SECONDARY High Voltage WINDING :

This is a large custom Shilchar 320 VA R-core Power Transformer. Unsolder the two high voltage secondary leads and clip lead re-orientate them, 180 degrees AC flipped.

Be very careful here, with lead dress and clip lead connections, as we are dealing with highly lethal 800 Volts of AC across this winding!!!!! Check twice before power up. Have your wits about you.

From the very first note played on Cut #2, “ Money for Nothing ” there was an easy to hear improvement. The amp played the music louder, more dynamic, and slightly more defined. There is a fabulous early guitar solo, stage left, and it was better now - than all the prior AC steps.

But the entire presentation was not quite right, not quite believable yet.. The guitar solo seemed to lack “ drive ” of the bottom portion of the guitar's body,... drive into the recorded space, and into my room. The high end of the guitar still seemed to predominate ever so slightly . The opening bass chords on Cut #1, “ So Far Away”, however were much improved...we were getting there.

Resolder High Voltage Secondary leads to their new 180 degree different orientation, and go on.

At this point in time, I had the following thought : “ I wish the nice audiophile Hong Kong client who will get this Chassis #2 amp, and Mr. Hari Iyer, were sitting in the room with me, to be able to hear and appreciate these subtle, cumulative changes. It would have been a great listening experience - for them both. All unmistakable.

AC TEST FOUR, the TUBE RECTIFIER FILAMENT wiring :

Same deal, unsolder the original two leads, clip lead and reverse polarity these two leads. This is a 5 VCT at 6 Ampere power transformer, custom Shilchar R-core, to power dual 5U4GB rectifier tube filaments.

Ohh my Goodness !!!! From the very first notes of “ Money For Nothing “, Cut #2 , the amp sounded appreciably better again !!! It played louder, with more dynamics, noticeably more energy into my listening room, in the X,Y, and Z axis. The opening bass notes in “ So Far Away ”, Cut #1, sounded AOK for the first time ( I love the ALTEC 515B 15 inch woofers ) , and totally believable to me. Guitar plucking that was in the background, and previously “ lost in the mix ”, was now being heard as distinct , on time, and defined. Resolution of subtle background accompanying voices, was now more distinct and better placed in all axis. The entire audio system played bigger, with more dynamic contrasting in the room.

Hey dear Forum friends, this is getting wild. There is a 50-50 chance that an AC connection is in best sounding phase. Now, we are at 80-20, after four of five AC orientation swaps !!

The wild guitar solo in Cut #2 showed signs for the first time, of proper harmonics, and energy, including finally, the lower body of the instrument. It still wasn't quite as good as I heard it with amp/chassis #1, but it really was getting there.

By this time, the listening session was long, and getting late in the evening. I thought of retiring for the night. But the unknown outcome of “ What would happen ” at TEST # 5, the FINAL AC orientation test, would have never allowed me to go to sleep. Any audiophile and DIY amp builder, worth their salt, would continue.

OK. OK. I soldered in the tube rectifier filaments to its new ( reversed and better sounding ) AC phase, and went on to unsolder and swap the last connection, the Output tubes AC powered filaments. Clip leaded them in 180 degrees opposite.

AC TEST FIVE, the OUTPUT TUBES' AC filament excitation.

Ohh my goodness again, from the opening note, the system played from the bottom up, cleaner, louder, and with more dynamics. Music resolution, definition, harmonic structuring, was “ off the scale .” The speakers disappeared in my living room, and the power and dynamic contrasting of the music was wonderful to experience.

Realize, this amp has a total of 12 Ohms DCR to the Finals tubes for B+ inductive filtering, and dual rectifier tubes, GTO capacitors, and much use of 12 AWG Mil Spec wiring. These corrected / optimized AC orientations, in all five circuit locations, allowed me to achieve a great and permanent music listening performance improvement, to be enjoyed on my nice friend's Beauhorn Virtuosos.

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Imagine starting this AC test procedure with a 50 -50 chance of some of the AC connections being ideal, and discovering that it was a 100% to 0%..... actual result. All were in need of swapping. ( Note : I am not sure of the very first test result ).

This overall amplifier improvement, with my type of circuit, and power supply, was substantial. F.M. Hari Iyer, I suggest for you to do your KT88 DC amps...... this same precise way . :)

At no time during this Chassis #2 testing, did I have the Softone RW-20 steel transformer covers mounted over the output transformers. It was an audible degrade, easily detected on my system. At no time during this testing, did I allow the two speaker lead polarities touch each other, in the distance between the new 6005 amp, and the speaker crossovers. They were suspended in mid-air. ( No polarity touch, no polarity twisting, eliminates loss of high end music information ).

One point I would like to make is, no one would get this performance, from this type of SE DC amp, unless they did this “ last 1 % ”, …....to finish the build properly !!

Another point. No manufacturer I am aware of, does all of this type of optimization, and I have never seen or heard a discussion among my fellow DIYer amp builders over the decades, about this procedure. Of course, we must all realize, I have not on-line researched this specifically, and I am certainly not privy to all that happens in tube amp builds on Planet Earth. :)

My knowledge of all of this comes directly from my mid 2019 KT88 SE DC amp build, where I was confronted with the use of multiple power transformers. I am self - taught. Any sincere questions, fire away !!

A++ to anyone who has read all of this post.

I hope, in future years, and for a few future DIY tube amp builders, that this approach does not get lost .

Jeff
Thanks Jeff for the detailed procedure fo the AC orientation. My curiosity is in all the 5 orientation you found the reversed connection to sound fuller, louder and much better. Doesn't that mean that you have reversed all the polarity by 180 deg. So only by reversing the AC wall outlet you could have obtained the same result?
 
Thanks Jeff for the detailed procedure fo the AC orientation. My curiosity is in all the 5 orientation you found the reversed connection to sound fuller, louder and much better. Doesn't that mean that you have reversed all the polarity by 180 deg. So only by reversing the AC wall outlet you could have obtained the same result?
Not quite Hari. Recall, in step ONE, I was swapping back and forth 180 degrees, several times.

What was better when I first started, cancer then, or polio then ?? LOL.

Actually, the transformers have a Primary and a Secondary which complicates matters. You have to get it correct, as to what sounds best, at it's four internal and individual points of AC use !!!!!!

Frankly, all I care about is, " on the swap, is it an improvement or a degrade " ??

Internally, we are only swapping the secondaries, Steps 2 to 5, and asking ourselves on each inversion, " is this better sounding or worse ", for each individual AC function ?

Which way do I want to solder it permanently ???

I honestly don't know if I am saying things that are technically correct as an explanation, and honestly, I don't care . Lets not lose the forest for the trees.

But I FULLY TRUST 100% what I heard in doing these two new 6005 DC SE amps, each amp in all five AC locations . No one else has ever done this so completely inside a SE amp, at least...... as far as I know.

Its so worthwhile in my amp builds...... to optimize individually these AC feed points as described. !

All I really care about is obtaining the cumulative end result.

Remember Hari, NO volume control, and only ONE set of interconnects, full bore in. Easier if you are not about 101 db like me.

Jeff
 
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3-06-22, NOTIFICATION : If anyone is tries to duplicate the above-discussed AC orientation testing, with their own SE amplifier, I have some advice to suggest :

1) Duplicate the described set up, such that only one set of interconnects, and no attenuation, ( ie : maximum signal coherency ) is in the chain.

We seek the full bore, best possible / least - loss signal music signal being fed to the amp being optimized.

2) Please note : " Solo Drums " is recorded in-phase, or with absolute phase coherency.

" Brothers in Arms " ( Knopfler ) however, is recorded 180 degrees out of correct absolute phase . Swap both channels' speaker leads if using Dire Straits, Brothers In Arms............ to do your testing.

3) Only proceed with the five AC polarity tests in the precise order as was described.

4) The TEST 2, of the Input tube's filament, this is often the most difficult to discern.

If you can tell no difference, you may have speaker wire issues ( amp to crossover ) ie: polarities touching each other, one or more times, in either or both channels. The only other possibility I can think of is your speakers are too low in efficiency to tell, and / or your system's overall audio resolution is not high enough.

5) After checking everything above, and there is still no audible difference for Test 2 ( the Input tube's filament feed ), feel free to try out TEST 3 next. If there is no difference swapping in TEST 3, cease testing . ( Your set up is not up to snuff ). If there was any difference in TEST 3 ascertained, ( and you permanently soldered in the two leads ) go back now to re-Test 2, re-try it. If Test 2 gives no clear polarity preference, cease your testing.

If, after performing Test 3 successfully, and then back to Test 2 successfully, please continue on - to Tests 4 and 5. Finish the optimization. Enjoy the overall result.

Jeff
 
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Out of curiosity, wouldn't one need to test 5 factorial (5x4x3x2x1 = 120) combinations to find the best combination of polarities?
 
Out of curiosity, wouldn't one need to test 5 factorial (5x4x3x2x1 = 120) combinations to find the best combination of polarities?

Hello Surfatwork !

Smart and good question.

I don't know the answer,.......... but I personally don't think so.

I feel, once you hear an AC orientation as the better of the two, you leave it there ( solder it in ) and go on, to evaluate and optimize the next AC feed in the circuit.

This above-outlined procedure has worked very nicely with a mid-2019 KT88 SE DC amp build, and it has worked great in both of these two new 2021-22 6005 SE amplifier builds.

If someone had the time and patience, however, they could go on after TEST FIVE - backwards .................and find out !!!


:) Thanks for posting !!

I have ordered two new Hammond 1627 SEA 2.5K Output Transformers for the upcoming 2022 " 6005 triple " SE design, just this past weekend. The die is cast. Next, order all the resistors, mainly ARCOL HS and Caddock manufactured.

Jeff
 
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Can't we just find out which is the addittive or subtractive polarity of the transformer secondary winding vis-a-vis the primary winding and connect all of them in the addittive polarity. That way we are also confirming what we listen.
 
Can't we just find out which is the addittive or subtractive polarity of the transformer secondary winding vis-a-vis the primary winding and connect all of them in the addittive polarity. That way we are also confirming what we listen.

I don't know Hari. What I do works !!!

How do you find things out?? With a scope? What if our " uniform " additive etc. assumptions are wrong ???? :) What if you set it up all totally uniform, and it is uniformly the opposite of best sounding, 180 degrees out ?

Can we even assume uniformity really IS the sought after format ???


I don't know.

How could you, or anyone, know and CONFIRM what is best sounding, without actually hearing it ?????

The only test I would trust - is hearing each individual AC orientation with clip leads.

It only needs to be done once, wires soldered in permanently, and enjoyed.

I have an advantage - been " working on " this topic, since mid 2019.

Jeff
 
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Out of curiosity, wouldn't one need to test 5 factorial (5x4x3x2x1 = 120) combinations to find the best combination of polarities?
Although your question is legitimate and well justified, it is the least matter of concern regarding this thread.
The fact of the matter is that those who are reading this thread are being subjected to nothing other than a voodoo assessment of audio performance.
Specifically and more importantly, the assertions that have been made in this thread are in direct conflict with and contradict well-documented and well-established principles in physics, mathematics. engineering and science that have existed for nearly a century,
With regard to your question, there is no basis for believing that a different starting point in the proposed fine tuning sequence is going to yield the same end result. Furthermore, there is no basis for expecting that a different listener who starts at the same point is going to end up with the same end result.
 
Although your question is legitimate and well justified, it is the least matter of concern regarding this thread.
The fact of the matter is that those who are reading this thread are being subjected to nothing other than a voodoo assessment of audio performance.
Specifically and more importantly, the assertions that have been made in this thread are in direct conflict with and contradict well-documented and well-established principles in physics, mathematics. engineering and science that have existed for nearly a century,
With regard to your question, there is no basis for believing that a different starting point in the proposed fine tuning sequence is going to yield the same end result. Furthermore, there is no basis for expecting that a different listener who starts at the same point is going to end up with the same end result.
I made no comment about whether such a test is warranted or not. Nor did I make any comment about whether such a test produces valid results. I also didn't share anything about my beliefs (I am Hindu, but not particularly religious, since you brought up the matter of beliefs...)
I merely pointed out that "if" someone wished to follow the procedure outlined above, for reasons best known to them, then one must test all 120 combinations of polarities in order to be exhaustive.
Kindly don't drag me into this morass of vilification that seems to be ongoing between you gentlemen.
Peace. Have a good day.
 
I made no comment about whether such a test is warranted or not. Nor did I make any comment about whether such a test produces valid results. I also didn't share anything about my beliefs (I am Hindu, but not particularly religious, since you brought up the matter of beliefs...)
I merely pointed out that "if" someone wished to follow the procedure outlined above, for reasons best known to them, then one must test all 120 combinations of polarities in order to be exhaustive.
Kindly don't drag me into this morass of vilification that seems to be ongoing between you gentlemen.
Peace. Have a good day.
You stated "I made no comment about whether such a test is warranted or not. Nor did I make any comment about whether such a test produces valid results. I also didn't share anything about my beliefs." That is absolutely correct, and I did not either say or imply anything to the contrary.
Perhaps in the future it would best if you simply quote me directly and refrain from attributing to me by implication positions that I do not hold,
 
An EXCITING visit to the 1911 firehouse on Sunday afternoon......... 2-20-22............ TESTING and SHOWING

When I first got there, I spotted my friend's new ALTEC “ H110 ” copies he had personally made. He found a write-up on this loudspeaker in a French Hi Fi magazine, and the plans were all in Russian, dimensions in millimeters.

These are an extremely rare speaker design. Built by ALTEC only between 1947 and 1949.

The highly popular A7 is only about half it's size. This H110 uses a single 515B woofer, one ALTEC 288 - ( a one point four inch exit compression driver ) on an ALTEC multi-cell horn ........a two way system. The 288 driver and it's horn seemingly reproduces music - virtually “ perfect ” from 500 Hz. up to 13 kHz.

A time-aligned super tweeter has been added.

If one thinks of an A7 as a half wave speaker, - then this is a full wave speaker. This H110's bass horn is much deeper and the bass horn's mouth must be twice as large as my A-7/ 825 enclosures'. Look at what greeted me, my jaw dropped :

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This above-shown audio listening room may be about twenty five feet wide, with about an 18 foot high ceiling, and is perhaps eighty five feet deep.

His workmanship on the speaker was absolutely lovely. He spent three weeks of labor on the build, during his COVID vacation. He used 9 full sheets ( four foot by eight foot ) of one inch thick Douglas Fir marine grade plywood, for both of the enclosures. A friend lent him access to his large well equipped wood shop, with precision German-made Festool equipment, that can cut and sand wood in a dustless manner.

The firehouse was built in 1911, when fire fighting equipment was only horse drawn. This particular location was decommissioned in 1933, because motorized vehicles could not get through the fire station's front doors, it was built to be only adequate for horses.

Take a look at the beautiful DIY job , done from scratch, by my nice friend. Those are one foot wide wings, on either side of the H-110 enclosure, which can be easily bolted on or off, as desired.



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My friend showed me his new belt drive turntable, tonearm, tube preamp and a new moving coil step up device which he had built over several days.

Notice the audio equipment pictured below. ( A temporarily placed CD player is obscuring on the top shelf .) It contains, left to right, his 300B stereo amp, 12AX7 phono stage, step up and belt drive table. A $16.500 pair of Thoress 845 mono amps were on the bottom shelf, collecting household dust. He told me in his system “ his 300B amp outperforms his Thoress 845 amps ”. He had the 300B is tricked out with very special capacitors and the very latest design of Western Electric's 300B output tubes.

My friend explained to me, the Thoress 845 monoblock is not a particularly bad sounding amp, but it requires a active gain stage preamp ahead of it. Why ? Reinhard Thoress beautifully built the amp with only two stages. The first tube stage, by itself however, does not provide adequate gain to allow the amp to perform to it's fullest, when using a passive preamp.

An active preamp becomes the amp's first gain stage, and it allows the amp to perform at it's best. Due to the amp's lack of adequate two-stage gain, the 845 amp will not ever exhibit a decent “ jump factor ”. It will thus pale in listening fun and mental involvement in my experience, VS a two stage amp that is specifically designed to have full and optimal gain in two stages. ( This design concept was covered in my 2021 6005 DIY amp build thread ). Remember the " 400 " resultant ???


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Wanting to hear his system as it was, my friend played me a few cuts from three different LPs.

I was not at all impressed. The system sounded muffled, gray, lacked dynamics, and was mid-fi sounding. This has sometimes occurred in the past when I would visit him. I did not tell him that. !! But I wondered - if - I could fix it ???

He was anxious to hear my amp, but I was not very sure we'd be able to assess it's qualities, the way this system was playing back music. In went my amp and triple Military Spec speaker cables. OK, same LP, stylus cleaned. A bit better, but still gray, murky, no life and no fun. I could hear “ hints ” of what my 6005 amp does, but some ( unknown to me ) things were holding us back - from really hearing it.

I then more actively “took control” of our session :


I brought with me a “ 3 into 2 ” AC plug adapter, an $0.88 cent part at Lowe's Hardware store. I had carefully filed down the wider ground prong, so that both prongs were the same width, and the AC plug with this adapter could be freely inserted 180 degrees, in either AC polarity.

I told my friend, my amp has been carefully AC polarity optimized by ear, in four or five different AC internal locations.

I said to him “ It will ONLY play properly if fed the AC properly. We two do NOT know over the years, HOW this 1911 firehouse has been wired . “ Please attach this AC adapter to the end of my power cord, and let us both hear it plugged in 180 degrees the other way .



BANG !!!!

From the moment the needle hit the record groove, the entire system sounded much much better.

We both heard that …..and agreed.

I had modified this inexpensive AC adapter for a client-friend of mine in Hong Kong, to send along in April 2022 with his new 6005 amp. He will self determine by his listening, his best-sounding Hong Kong AC polarity feed, within the first hour of music playback !!!

We both listened for another 15 minutes of so. I was still not too happy I asked my friend “ Are these 515B woofers playing out of phase??” Oh no, Jeff, I checked that very carefully. ”

“ Fine said I, but maybe this source material, the LP Record, is recorded out of phase”. “ You have to mark all your sources as to being recorded IN or 180 degrees OUT of phase, and play each back properly. ” He understood that.

I then asked “ Is it OK if I swap the negative and positive speaker leads, on both channels of the new 6005 amp” Sure he said. .............................. The needle hit the groove :



BAM BAM ….............BINGO !!!!!!!

The whole system came alive, top to bottom, front to back. It played within 85% of what I have at home. The French made jazz test LP, had been recorded ( both channels ) 180 degrees out of absolute phase. It now finally sounded VERY VERY good to both of us. Great plucked bass playing , etc etc. Piano playback was thrilling. Wow. Allen Toussaint.

With that, I said, “ use it for a week and return the amp to me. I also said, Isn't it amazing, but perhaps nothing can out-play this particular 6005 amp, as presently built...... in all of audio today !!

I also went on and said “ remember two months ago, I had you buy two GE new-in-the-box 6005 output tubes, both for ten dollars plus shipping on eBay !! ”

" No one now, except me, knows what this new amplifier design can do. Me first, and secondly you .....after this next week. "

I next said, “ Compare the 6005 and my new amp to any output tube that costs $300.00 each, and the $5.00 GE 6005 I had you buy - will absolutely KILL it. ”

My friend then interrupted me and said “ Jefferey, the tubes in my 300B amp are the brand new Western Electric design, I paid $1,500 each for them. I will listen all this next week, have friends over, and try to wrap my head around this ”.

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My friend asked me to summarize his findings to you, VS: his tricked-out 300B amp.

He found the new stereo 6005 amp to play well. It played wider and a more accurate sound stage in the X,Y, and Z axis. He reported it to be lusher sounding. It also had a noticeably more extended and detailed high end. His 300B amp, on the other hand, had better SLAM on the low end, and portrayed more “ meat on the bone ” in the middle mids.

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I was very satisfied with his subjective input.

I explained to my friend, a single miniature 6005 power tube, with a 12 Watt rated plate, running only 33 mA., will at best put out perhaps 3 Watts. I does not have much current available to control the woofer. The much larger 300B tube has a 40 watt rated plate, idles at maybe 80 mA. of current, and may put out a solid 8 Watts of power. Compare these two tube numbers !!

As to “ meat on the bone” in the middle midrange, I explained that this is the range his 300B amp plays in, ( and most SE amps are designed and able to play. ) Mostly mids, but not ever TRULY wide band. Your ear will perceive it, just as you did.

My friend and I agreed, that for his listening room, and with his new speakers ( each with a 25 cubic foot bass enclosure volume !! ) he needs to wait for me to next build the already - planned 2022 “ 6005 triple ” amp. We both need to give that a good listen on his system. It will be 9 Watts output and have 99 mA. ( 33mA. times 3 ) of idle current. Probably perfect ....... for his fire house system.

The main purpose of the next triple 6005 amp is to give it more power, (1) so as to be able to play more people's speakers, and (2) to have the inherent ability to “ man-handle ” all of the lovely sounding 15 inch ALTEC woofer drivers ( 515Bs / 416Bs / 604s ) myself, and many of my audio friends use.

MY REPORT : The 6005 tube itself, ( as I am running it ), is far superior to any other output tube I have experienced in all of my listening, such that I do not mind paralleling three ( matched and balanced ) tubes in the output stage. ( VS one single 6005 output tube, which plays purer . )

What little fidelity that is given up by paralleling, will be more than made up overall, by my own “ triple's ” implementation, in terms of a total usable audio performance and .......as a really fun to hear listening experience.

The little 6005 tube itself, in my implementations, may subjectively exhibit two times the transfer efficiency, of any other output tube I am personally aware of. There exists (1) round and thus fully symmetrical construction of the cathode, grid and plate - and (2) ultra-close element spacing. This likely creates it's subjectively superior transfer efficiency . As more people get to hear these latest stereo 6005 amps, this will come to be understood....... and appreciated. Three DIY ones, are scheduled to be built by friends.

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A couple more photos, of the newly cloned 1947-49 H110 follows. My builder-friend over the years has accumulated enough fully rebuilt vintage ALTEC drivers and multicells, ( and experience ) to be able to build four more pairs , if demand exists.


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IMG_8631  left rotated.jpg


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It has certainly been a joy to be able to share this with you. I hope you enjoyed the post !!! Try not to be overly serious or critical . We are truly having FUN in our audio hobby !!!

Jeff
 
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03-09-2022 .........................................What is wrong with this picture below ??????..........................................


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( Note, Posting software stuck on BOLD, ....sorry .) :)


No need for others to copy implementation errors shown above. There are two things wrong in the photo. Can you spot them ????

FIRST ERROR :


The fancy high end German three way crossover build should NEVER have used two tie wraps to bundle the twelve lead wires - coming out of it.

It truncates the high end, a sense of air, and it reduces the lower harmonics ever so slightly. Maybe a 1% to 2% subjective system degrade.

Within 20 minutes of arriving, I had my friend cut the tie wraps off, and throw them away.

He neatly spread the twelve wires 1/8th an inch or more apart from each other - so that they did not touch and their fields would no longer interact.

The German Manufacturer - should have done this !!!


SECOND ERROR :


My friend should have never ever twisted those red and black wires, from the German crossover leading to the tweeter.

In a sensitive high efficiency speaker ( only IF you happen to have an amp designed to play the high end well ), you are ruining the high end system's response.


In such a wide-band system, ANY time the speaker wire polarities touch..........just once.......it degrades the entire top end, down into into the mids and lows.

This is due to resultants that travel down the frequency range into the lower ( and easily heard ) areas of sound reproduction.

An E.E. type would know that the two speaker wires touching each other increases their total capacitance, what ever the heck that means . :) Note : I don't personally much care about the theoretical reason, only the subjective listening result matters to me !


In such a system, ( such as what I run ) one can not have the speaker wire polarities touch each other, for the entire amp-to-crossover, distance, and crossover to drivers distance,..... even one time !!!

Polarities touching can become up to a subjective 3 to 5% system degrade. A lot less real sounding !!! Harmonics, timbres, sense of air, and dynamics, all suffer. I just named it, and it all gets degraded . No FUN !!

My friend tells me he has Dueland speaker wire, and he will replace the twisted lengths.

I hope he remembers to cut the new wires to 57 1/8th inches, a Bob Fulton discovered compromise length. He might likely have to adjust the tweeter's signal level down some, but maybe not, when using his 300B ( midrange playback primarily ) conventional SE amplifier.

It may be very difficult to hear what I am describing, with conventional SE amplifiers, that do not play wide band . Don't blame me. What was described exists !!

Can any audio system play back cymbals in a drum kit faithfully ??? That certainly is one of my system design goals ( eg : the CD, Solo Druns - Clarke ). This is not easy for anyone, myself included, to accomplish.

Have fun listening !

Jeff
 
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Nice work, my friend!
With regard to the "Nice Work" which you mention, are you referring to the build itself or are you also referring to the senario of reversing polarities of power transformer secondaries that are alleged to result in increases in loudness? If it's the latter, would you please explain how switching polarities of power transformer secondaries produces the claimed loudness increases for the same input and without any change in amplifier gain. Based on decades of psychoacoustic research on loudness, it is a well documented and well established fact that loudness is a monotonic function of sound level, which means that an increase in loudness can only be produced by an associated increase in sound level, which in a situation using the same source material, would require an increase in amplifier gain. But, as you well know, reversing the polarities of power transformer secondaries has no effect whatsoever on the gain of an amplifier. Hopefully you can shed some light on the seemingly inexplicable increases in loudness that are claimed to result from reversing the polarities of power transformer seondaries. .
 
This is due to resultants that travel down the frequency range into the lower ( and easily heard ) areas of sound reproduction.
What exactly is a "resultant"?

Also
I had modified this inexpensive AC adapter for a client-friend of mine in Hong Kong, to send along in April 2022 with his new 6005 amp. He will self determine by his listening, his best-sounding Hong Kong AC polarity feed, within the first hour of music playback !!!
Hong Kong uses British BT 1363 plugs and runs 230v at 50hz. So how does an American 3 to 2 wire adapter fit into this? Some 60hz power transformers will overheat at 50hz as they lack enough inductance for 50hz. Did you consider this when exporting your amps?
 
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