drlowmu's (Jeff's) Amp Discussion

drlowmu

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I too have been looking for a good amplifier, ..........for over 50 years now.

In high end audio, you first need to have a two way speaker that is 101dB or more efficient. 98 dB won't do. Think vintage movie theatre. ALTEC purchased used, can be a great speaker choice. Own a professional-use speaker, NOT a " designed for-the-consumer " speaker that seems to get mentioned in this thread !!

Only then, .........................are you able to find the really really good amplifiers.

These amps will have :

a) no negative feedback in them, and

b) will be 2 Watts or less.

Amps are the real turkeys in audio. Most amplifiers, but not all, are a travesty - terrible.

I have had to learn to design and build my own amplifiers, to get satisfactory performance !!!

Good luck.
 
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In high end audio, you first need to have a two way speaker that is 101dB or more efficient. 98 dB won't do. Think vintage movie theatre.
So, a middle class audiophile in space-starved metro apartment can never have high-end audio*? Or are there any small sized speakers that are above 101 dB?
 
I too have been looking for a good amplifier, ..........for over 50 years now.

In high end audio, you first need to have a two way speaker that is 101dB or more efficient. 98 dB won't do. Think vintage movie theatre. ALTEC purchased used, can be a great speaker choice. Own a professional-use speaker, NOT a " designed for-the-consumer " speaker that seems to get mentioned in this thread !!

Only then, .........................are you able to find the really really good amplifiers.

These amps will have :

a) no negative feedback in them, and

b) will be 2 Watts or less.

Amps are the real turkeys in audio. Most amplifiers, but not all, are a travesty - terrible.

I have had to learn to design and build my own amplifiers, to get satisfactory performance !!!

Good luck.
Food for thought. I have never heard a 2 watt amp with a 101db speaker. They must be either very expensive or not popular. if popular the market now would be flooded with them, I think?
Do share more thoughts on why low watt+high sensitivity makes for better music reproduction than high watt+low sensitivity combinations.
On a lighter note @Arvind Singh Lodhi shared this. (@drlowmu This is not meant to abuse your approach)
1623466884421.png
 
So, a middle class audiophile in space-starved metro apartment can never have high-end audio*? Or are there any small sized speakers that are above 101 dB?
You understand me correctly !! Very good. For the average space starved metro apartment, , NO, you can not have true " high end " as "'I" have herein defined it. High efficiency speakers are not small. One needs to start with a 101dB or better speaker, to be able to use the best sounding ( under two watt ) amplifiers.

I am " middle class " economically, and I personally was able to obtain what I speak about, but only after many years of audio-equipment-struggling, and after a lifetime of effort.

Food for thought. I have never heard a 2 watt amp with a 101db speaker. They must be either very expensive or not popular. if popular the market now would be flooded with them, I think?
Do share more thoughts on why low watt+high sensitivity makes for better music reproduction than high watt+low sensitivity combinations.
On a lighter note @Arvind Singh Lodhi shared this. (@drlowmu This is not meant to abuse your approach)
View attachment 58017
I am an amateur tube amp designer. I make Single Ended direct coupled amps for many years. As soon as you go to bigger tubes, to get more power, ( eg : a 300B, or an 845 ) there is a sonic degrade in the overall music / performance level. The best sounding Single Ended tube amps, in this world, in my experience, are always 2 Watts or less. To enjoy the best, takes a 101 dB speaker. Very simple !! You have to get it right with the speaker, first, if you want to have the best possible amps to listen to.

You are correct, the popularity of such amps is extremely small. Probably only a handful or two exist. Mainly because most E.E.s and amp builders do not have a good " feel " on how to make them, ...and world-wide this applies !!

But some exist, and they are cherished by their owners. It has taken me over 40 years of tube amp building, to get to a point where I am finally happy with amplifier performance. See my 6005 amp build thread, in "DIY" Forum. This new design has a good chance to be among the very best sounding of audio amplifiers, ever built !! I recall a post listing the many ways in which it differs, in the thread.


Have fun, and good luck to you.
 
I concur with you. I have ventured into tubes for last 20 years and have gone through every set of SET amps and come to a similar conclusion. The most seductive is SET 2a3, then 300b, SET 845, SET 6C33C, SET GM 70
 
I concur with you. I have ventured into tubes for last 20 years and have gone through every set of SET amps and come to a similar conclusion. The most seductive is SET 2a3, then 300b, SET 845, SET 6C33C, SET GM 70

Thanks. Good post !! Readers - take note, at his experience.

A 300B has a 5 volt filament, and so, it requires DC heating. A 2A3 ( eg, modern monoplate - better than vintage biplates ) will have, like all 2A3s, a 2.5 volt filament. This ( lower ) 2.5 volt filament requirement of a monoplate 2A3 tube, allows for simpler AC heating.

AC heating of such a 2A3 DHT Finals tube always ( to me and others ) sounds better than DC heating.

If you have 101dB ( or higher ) speakers, you can easily, comfortably get by with a 2A3 amp, as you will be running at 1/4 to 3/4s of a Watt, most of the time.

To play the game, you have to have the right speaker. .... to be able to use the best sounding amp....assuming you can discover what that is !!

I use ALTEC 515B 15 inch woofers, with absolutely NO crossover on it, and ALTEC 802D high-frequency compression drivers. The simple two-way speaker combo is about 103 dB efficient, horn loaded.

P1010021 EDITED.jpg
 
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So, a middle class audiophile in space-starved metro apartment can never have high-end audio*? Or are there any small sized speakers that are above 101 dB?

Hi Sachin, while I cannot comment on the post you quoted or the rest of it, please understand that efficiency needs size, the lower in frequency the efficiency extends the greater the size of the enclosure. For maximum efficiency done "according to theory" one would need a rather large horn to go into the bass regions, often people say that if you want proper loading then you need 1/4th wavelength horn path in the enclosure, and that's the minimum. Some people even insist on full wavelength. At 100Hz 1/4th wavelength is about 2 feet 10 inches. So if you apply this to many speakers you will notice most do not even come close to 1/4th loading at 100Hz. At higher frequencies this is easier but still requires some size for a proper horn, as there are requirements for the horn mouth size etc. That enables proper directivity. I mean no offense to anyone but if they believe they are getting a 2 way book shelf size speaker with a dome tweeter and a 6-8" mid/woofer which is 101-102db at 1W/1M then they are likely mistaken.
 
I agree with drlowmu. The combination of high sensitivity fulllrange with fleawatt SE amplifier is something mystical as well as magical. Difficult to describe,until experienced. I learnt this after starting to build SE amplifiers. For space starved audiophile,a reasonable compromise is to use philips hi q speakers in a mass loaded transmission line or Even a 4 inch Tabaq with Faital pro. These are no way near to 101dB, but will give 95dB and 90dB in that order. Good enough for small listening rooms as I'm metros apartments.
I agree that negative feedback kills the sound. But of late i am experimenting on local feedback techniques ( anode to grid or anode to previous stage anode). They look promising. Far better than Global feeo that's taken from the Secondary of OPT.

I am now working on building a SE amplifier using E180F and PL504. Gives about 8 watts. All the power transformer,choke and OPT are handwound by me. Will post pictures on that in due course
 
How low do these high efficiency speakers powered by less than two watt amps go?
 
The prevailing attitude seems to be that, it is better to have more watts and not need them than not have them, then need them. Why be restricted to the kind of speakers one has to use?

saw this too:
 
The prevailing attitude seems to be that, it is better to have more watts and not need them than not have them, then need them. Why be restricted to the kind of speakers one has to use?

saw this too:
So it also boils down to what music one likes to hear. The thread seems to suggest, from the experiences of many users, that extreme low watt (SET) amps don’t bring out the dynamics well.

Guess it must be a designers’ dream to get both the mid-range magic and dynamic sound from the same amp. Which amps, in an affordable range (say below 2 lacs) achieve this combination the best? Especially any amp that can drive speakers around 88-89dB?
 
Some maths and facts.
The first watt is the most important watt. Majority of the musical listening happens less than one watt.A headroom of 2 more watts is safe to accommodate those Crescendos.
2. Class A amplifiers by design gives distortion free music even at sub watt levels.
3. An amplifier which is rated for 100 watts, will sound double loud as that of a 10 watt amplifier ( not 10 times!)
4. Using the same amplifier at same volume setting,a speaker of 95dB sensitivity will sound twice loud than when using a 85dB speaker.
5. To summarise, A 2watt amplifier powering a 105dB speaker will sound as loud as a 200watt amplifier powering up a 85dB speaker.

Hope this helps.

As far as dynamics, SE amplifier have a special sound signature,They have restriction in producing low frequency notes with a punch, because of core saturation happening in SE output transformers. PP design does not have that , so can give more punchy bass and may be more subjective dynamics. SE amplifier have a property to reproduce human voices and instrumental timbre with almost life like presentation. It's not that it's weak in dynamics or bass,the truth is our ears have been tuned more to a bloated bass than what actually it is.Hear a SE amplifier and then your perception of bass will change. It's not about punching , it's about just enough bass at just the right time., One can say more natural bass or bass as it is intended to be.
 
Hi Sachin, while I cannot comment on the post you quoted or the rest of it, please understand that efficiency needs size, the lower in frequency the efficiency extends the greater the size of the enclosure. For maximum efficiency done "according to theory" one would need a rather large horn to go into the bass regions, often people say that if you want proper loading then you need 1/4th wavelength horn path in the enclosure, and that's the minimum. Some people even insist on full wavelength. At 100Hz 1/4th wavelength is about 2 feet 10 inches. So if you apply this to many speakers you will notice most do not even come close to 1/4th loading at 100Hz. At higher frequencies this is easier but still requires some size for a proper horn, as there are requirements for the horn mouth size etc. That enables proper directivity. I mean no offense to anyone but if they believe they are getting a 2 way book shelf size speaker with a dome tweeter and a 6-8" mid/woofer which is 101-102db at 1W/1M then they are likely mistaken.
Good post. The ALTEC A7-8 VOTT speaker I have pictured above has a 135 hZ, sized horn mouth, and the bass reflex port takes over, below that frequency. You can see the big grill cloth covered port at the front, bottom.

How low do these high efficiency speakers powered by less than two watt amps go?
Good question.

My audio mentor builds a 10.75 internal cubic foot MLTL ( mass loaded transmission line ) speaker out of 1 inch Euro Ply. It houses a GPA ( Great Plains Audio ) 15 inch "604" duplex speaker, successor to the ALTEC 604s of long ago. I have heard it at audio shows play a fabulous, articulate , super fast low end, subjectively GUESSED to be in the mid 20s, using his SE 2A3 amplifer. ( 2 Watts clean ).

My speaker, pictured several posts above, an ALTEC VOTT ( Voice of the Theatre ) A7-8. It only goes down to about 50 hZ., using a similarly powered amp.

" Only 50 hZ." you will say. Guess what, it does not bother me at all!! ( for many years, I used speakers that went from 12 hZ to 100 kHZ., a 7-way Fulton Premiere speaker system ) Why now, should I accept 50 hZ on up?? Why ?? I feel, and I believe, I may have the best possible mid bass in audio. What causes that ??? Three things,...........and all these three are required, simultaneously :

(1) An absolutely world-class SE amplifier
(2) a ALTEC 515B 15 inch woofer ( or a new GPA 515H, expensive, which will go down to 40 hZ, not 50 HZ) and
(3) having a FRONT radiating woofer and a FRONT LOADED 135 hZ. short-horn, in front of the woofer. ( my ALTEC 825 enclosure with minor mods ).
 
How low do these high efficiency speakers powered by less than two watt amps go?

Speakers are not made for a particular amp in general unless it is being sold as a system or is an active/powered design. To answer your question the speakers could have extension to any frequency which would be dependent on the design. In the modern era most people use ported systems to go low as it achieves a *smaller* box size than a proper horn, this however does not mean that said ported box will be small in general terms, they could be pretty big.

The prevailing attitude seems to be that, it is better to have more watts and not need them than not have them, then need them. Why be restricted to the kind of speakers one has to use?

saw this too:

I don't know about others but I choose my own speakers and amps irrespective of the prevailing "wisdom" among any "camp". That is how it should be IMO.
 
The prevailing attitude seems to be that, it is better to have more watts and not need them than not have them, then need them. Why be restricted to the kind of speakers one has to use?

saw this too:
That may be the prevailing attitude. But this was posted on the " High End " forum. Mid-fi / popular ideas are not prevailing here.

One is restricted to 101 dB and higher speakers, because AMPS, not speakers, are the biggest , weakest problem in audio, IN MY OPINION. 99.99% of amplifiers flunk miserably.

Your referring us ( in your post ) to " Saw This Too" ................ totally backs up what I am telling you all.

Every one of those commercial SE amps, are positively terrible - junk, at reproducing dynamics !! The manufacturers copy 100 year old E.E. schematics, and apply no new thought as to how to engineer an amp for maximum dynamics and highest audio performance. That is what the public is " stuck " with. The blind manufacturers ............leading the blind.

A 101 dB speaker requirement as a start, allows one to use the best POSSIBLE amps sonically, which are 2 Watts or less.

Honestly IMO, appropriate amps
are in the 00.001% spectrum of product availability !! Look at my 6005 SE DC amplifier thread on this Forum. There you can view me tackling the best possible 1.5 Watt amp I know how to build, in 2021. It has dynamics and a sense of presence that will scare the listener, it is so realistic !!

I have to design and build my own amps, to get the performance I personally desire !! But I can and personally DO get it - maximum dynamics and the capability to play back most of the musical instruments realistically. What does it take ?? Look at my 6005 SE DC amplifier thread on this Forum, "DIY". There, you can view what likely will become the world's best performing 1.5 Watt amp in audio.

I spelled out the design and engineering reasons "why", right in the thread.

More amplifier "watts", over two, in High End audio, is typically a poorer sounding amplifier !!

If someone seeks High End performance, it is easiest if they start with the right speaker. Then tackle the ( huge ) amp problem.

There is one exception to the above I have heard ( short term ) at a show, liked,.... and it costs a million USD. A complete MBL system, Radialstryler Omni Electrostatic speakers and their MBL electronics from Germany.

All I wrote herein is only my personal OPINION. This is my direct / hands - on personal experience, after messing with High End audio for 76 years. YMMV, fine with me !! Best wishes.

Jeff
 
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Good question.

My audio mentor builds a 10.75 internal cubic foot MLTL ( mass loaded transmission line ) speaker out of 1 inch Euro Ply. It houses a GPA ( Great Plains Audio ) 15 inch "604" duplex speaker, successor to the ALTEC 604s of long ago. I have heard it at audio shows play a fabulous, articulate , super fast low end, subjectively GUESSED to be in the mid 20s, using his SE 2A3 amplifer. ( 2 Watts clean ).

My speaker, pictured several posts above, an ALTEC VOTT ( Voice of the Theatre ) A7-8. It only goes down to about 50 hZ., using a similarly powered amp.

" Only 50 hZ." you will say. Guess what, it does not bother me at all!! ( for many years, I used speakers that went from 12 hZ to 100 kHZ., a 7-way Fulton Premiere speaker system ) Why now, should I accept 50 hZ on up?? Why ?? I feel, and I believe, I may have the best possible mid bass in audio. What causes that ??? Three things,...........and all these three are required, simultaneously :

(1) An absolutely world-class SE amplifier
(2) a ALTEC 515B 15 inch woofer ( or a new GPA 515H, expensive, which will go down to 40 hZ, not 50 HZ) and
(3) having a FRONT radiating woofer and a FRONT LOADED 135 hZ. short-horn, in front of the woofer. ( my ALTEC 825 enclosure with minor mods ).
Appreciate the clear and specific feedback @drlowmu. I am so used to the 20 (?) - 50 hz experience now that I miss it when it’s not there. Please correct me if I am wrong, but good powered subwoofer can further augment the signal from very low powered SET amps to lower than 50hz bit. I am no expert on electronics, but I remember being informed that its the voltage from the amplifier that matters to a powered sub with its own amplification? So a pre amp level voltage @2v should suffice?
 
I am so sorry about this above post. I copy and pasted - re-wrote a paragraph, and left both paragraphs in there. My mistake. No way to correct / edit the duplication now - after the first hour's showing. Sorry !! It now appears as though I was doubly bragging. That was not the intent !!! I was only telling you things, as experienced .

In that amplifier build thread, I found that post discussing how my tube amp-lifier design differs - from everyone's conventional tube amp.

Sixteen design areas, each of which I find are ultra-important - are incorporated in this 2021 tube amplifier's build !! See them all listed here :


The S.E. 6005 amp project is moving along nicely, making decent progress - over the last two days. In India, F.M. Harry Iyer, and Sadik, have been fabulously assisting. Thanks guys !! .

Tonight, we are 90% done the CAD drawing work of the 14 gauge welded steel stereo chassis. With the needed CAD files, half a dozen chassis are to be machined, starting next week, at this shop : www.4mmc.com

Purchase Orders for R-Core power transformers were initiated just yesterday in India, with a Distributor of Shilchar Technologies. The new amp has a computed 96 VA power draw, and a 320 VA sized R-Core power transformer is to be used. Large enough.

Jeff

Appreciate the clear and specific feedback @drlowmu. I am so used to the 20 (?) - 50 hz experience now that I miss it when it’s not there. Please correct me if I am wrong, but good powered subwoofer can further augment the signal from very low powered SET amps to lower than 50hz bit. I am no expert on electronics, but I remember being informed that its the voltage from the amplifier that matters to a powered sub with its own amplification? So a pre amp level voltage @2v should suffice?
In my opinion, a subwoofer is a piece of junk, to be avoided - it is for mid-fi use only by the masses.

Why ?? It usually has a different amp on it, and so, it plays out of time, out of coherence, and with a different sonic signature. If a person uses more than one amp on a system , as in " biamping ", there is ONLY one correct way to do it. All four amplified channels in a stereo biamp, ( upper and lower, left and right ), MUST be exactly the same. It almost never is !!

But with biamping you still will lose out. Why ?? Because you need to add a whole EXTRA set of active electronics, line level, to initiate and feed the biamp's split signal. There are fidelity losses going through ANY extra stage.

Simplest is best. With loudspeakers, practical / simplest in my experience, is a two way speaker system. A one-way speaker, a single Lowther, etc., won't hack it. 101dB or higher, direct front-radiating, and hopefully, front-horn-loading, with a 15 inch quality woofer is satisfactory.

The three best high-quality drivers I know of in this world are professional :

1) vintage Klangfilm,

2) ALTEC, or

3) ALE ( $$$$ ) from Japan, a Q-Ced copy of an ALTEC .....at 20 times the cost.

Klangfilm, professional German movie theatre speakers, from pre WW2, are unobtainium.

My ALTEC 515B 15 inch plays from 50 hZ. to about 3.5 khZ, with out a crossover on it. Driven-directly, 8 AWG equivalent silver-content speaker wire, from a 1.5 Watt DC SE amplifier. Less, is more, but only IF you have great great equipment. Analogue sources, directly-coupled two-stage tube amps, silver-content speaker wire and a 101 or higher dB two-way speakers.

Recall, my friend's 10.75 cubic foot GPA MLTL plays into the mid 20s, subjectively to my listening. Have you forgotten that ?? This plays down low using a fabulously designed 2 Watt 2A3 amp.

If it were important to me, to have mid-20 s response, I would copy his speaker design.

But overall, I only prefer to hear my front-horn-loaded 15 inch play into my living room. My friend's MLTL speaker is on a flat baffle. Not for me !! A front-radiating, front-loaded horn, with an ALTEC 15 woofer in it, in a VOTT enclosure, has spoiled me rotten - for life - I think !!

Have fun, I am now, finally !!

Jeff

It took me a long time in audio, with much high end equipment coming and going, to arrive at my present system. Recall, I owned seven-way speakers that measured, the widest band ever in their day,( plus or minus 2 dB, 12 hZ to 100 khZ. ) So what ! The amps needed to drive it were PIGS. Now, I am happy with MY self-built amps, and 50 to 15 kHZ playback. It only took me about 40 years to arrive here !!
 
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@drlowmu, I honestly couldn’t understand a lot of what you said (my technical prowess is limited) in the post above, but I do appreciate your passion.
Forty years quest and experimentation is a very long time of learning and I am happy you found contentment in what you have designed and fabricated.
Enjoy the music!
 
And thr original thread owner will go mad reading all this …
LOL, maybe so.

I just wanted to express my opinion publicly, as I know I am in a great minority, ....... which is OK .

I wonder, if I read such a thing as I have posted in this thread, fifty years ago with me at age 26, how my audio journey to find happiness might have differed. But we didn't have Forums and the WWW back then. Just snail-mail letters, lots of letters written.

The people on this Forum are very gentle, thoughtful. I get a good feeling from all of you, as human beings. Thanks for being who you are !!

Jeff

I concur with you. I have ventured into tubes for last 20 years and have gone through every set of SET amps and come to a similar conclusion. The most seductive is SET 2a3, then 300b, SET 845, SET 6C33C, SET GM 70
Also " seductive" device, maybe more so than a single plate 2A3, is the smaller, simpler ( essentially half size) Type 45 tube. But, the Type 45, in a vintage ST or globe shape, has a fatal flaw, seldom widely recognized.

It is not useful in playing a full range efficient speaker, with a 15 inch woofer.

It flunks in playing the mid bass chords' energy of a concert grand piano, in a full-range playback audio system It is thin sounding in that particular piano range, and it is purely due to faults in that tubes' ( cheap, mass produced 1930s ) internal materials and construction. On 101 dB or higher speakers, the 45's overall power is OK, but it has inadequate linear power in that very important piano range. Other smaller 10 and 12 Watt ( plate ) finals tubes will play there linearly, where a ST or Globe 45 simply can not !!

The Type 45 ST is fabulous, for a vintage table radio. Not appropriate as a choice, for full range playback of a concert grand. Sorry.

A two dollar more modern tube ( 1950s ) 6AQ5, IF properly, carefully implemented, easily can out-play a Type 45. No one ever "fix" a ST Type 45 tube's weaknesses on a concert grand piano. Its a playback weakness of this vintage tube, and not the associated amplifier.

Once I fully recognized the ST and Globe 45's " fatal flaw" in about 2018, I sold-off every one of about 40 pieces I had collected on eBay. I bought GE black plate 5 star 6005s in its place. The " firecracker" tube - in instantaneous playback energy from the efficient speaker. Symmetrically constructed internally !! See my other thread, for my own take on an appropriate amplifier design.

Jeff
 
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In my opinion, a subwoofer is a piece of junk, to be avoided - it is for mid-fi use only by the masses.
I fully concur with you on this.
And your reasoning - out of time, out of coherence.
I have seen people using subs with high end speakers such as PMC which ruins the superb qualities of such a speaker design just for the sake of getting lower and more bass.
So to each his own and back to the topic of a good amplifier.
 
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