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New Design, SE 6005 Directly Coupled Audio Amplifier

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IndianEars

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My opinion only, I much prefer passive filtering. Less of a thumbprint, less parts, and less noise.

A voltage reference tube, as part of any regulator can oscillate whereas a shunt resistor will return the B+ hash to ground.

Also, there is no substitute for thoughtful use of hash chokes in tube amps, to remove noise, stabilize an amplifier, and make it sound better. Hash chokes can have a very positive effect on performance !! They often could be used to clean up the output of solid state regulators, when found in tube amps. ( eg : SP3A-1 preamps benefit greatly. ) There are more subtle ways to use hash chokes to good effect. The new 6005 prototype already has six hash chokes in it, and I now plan top add four more in a upcoming rebuild !!

A shunt resistor must be chosen for its sonic characteristic. We do have quiet and great sounding shunt resistors in 2021. My 6005 amplifier uses modern Caddock " power tabs " as the resistor to ground. ( Types MP-820, MP-930 and MP-925. ) Other acceptable shunt power resistors I use are vintage Ohmite Brown Devils, Mills MRA-12s, and ARCOL HS series chassis mount power resistors - which are engineered for pulse duty.

Back to the subject of R-Cores : Kitamura Kiden, who invented the R-Core in 1978, has McIntosh ( USA ) as a customer. We can learn about this Japanese company, who also supplies Softone their products, here :

http://kitamura-kiden.co.jp/product/rcore/

I hope this post is of some assistance to FMs.
SUPER Post on MANY counts, including the selection of Shunt Resistors. Many Thanks!

I am surprised about McIntoch... They have always made much that their Output transformers are all wound in house.
 

IndianEars

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I did a quick Google check on McIntosh using Kitamura Kiden R-Core Transformers.

I have reason to suspect that this is not true .... :(

This is the Kitamura Kiden page that says:
"Our customers include major domestic Japanese companies such as Shimadzu, Toshiba Schneider Inverter, Toshiba Medical Systems, Hitachi Medico, and Hitachi Machine System. We also have many major overseas clients such as Mackintosh, GE, and Varian Medical Systems."

None of these are Audio Equipment manufacturers, and the spelling of Mackintosh, is completely different from the Audio Company McIntosh Labs.

A search for Mackintosh put out this page on Linkdin :)
 

drlowmu

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I did a quick Google check on McIntosh using Kitamura Kiden R-Core Transformers.

I have reason to suspect that this is not true .... :(

This is the Kitamura Kiden page that says:
"Our customers include major domestic Japanese companies such as Shimadzu, Toshiba Schneider Inverter, Toshiba Medical Systems, Hitachi Medico, and Hitachi Machine System. We also have many major overseas clients such as Mackintosh, GE, and Varian Medical Systems."

None of these are Audio Equipment manufacturers, and the spelling of Mackintosh, is completely different from the Audio Company McIntosh Labs.

A search for Mackintosh put out this page on Linkdin :)

Of course it is true.

I have seen photos of R-Core XFRs inside McIntosh equipment, in recent years.

I have seen a published schematic of Nobu Shishido's Loftin White 2A3 DC amplifier, and it was mis - translated by the Japanese as Roftin- White, a R-W 2A3 amplifier !!! I think that - is funny !!

As I have already pointed out, it is early in audio's adaptation to R-Core output transformers. Only a few people in audio today actually realize what they do !!

I feel the R-Core audio output transformer easily out-modes, all that has come before, in terms of it's design and performance !! No contest overall, between a Softone R-Core and all the others, what-so-ever.

I also suspect that Softone and the Japanese do not yet fully realize this. Their tube amplifier build capability lacks what some of us in the USA do, to make vivid aural determinations.
 

drlowmu

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I did a quick Google check on McIntosh using Kitamura Kiden R-Core Transformers.

I have reason to suspect that this is not true .... :(

This is the Kitamura Kiden page that says:
"Our customers include major domestic Japanese companies such as Shimadzu, Toshiba Schneider Inverter, Toshiba Medical Systems, Hitachi Medico, and Hitachi Machine System. We also have many major overseas clients such as Mackintosh, GE, and Varian Medical Systems."

None of these are Audio Equipment manufacturers, and the spelling of Mackintosh, is completely different from the Audio Company McIntosh Labs.

A search for Mackintosh put out this page on Linkdin :)

Notice this : the Linkdin report on John Mackintosh ( an E.E. ) has nothing to do with any audio involvement - going back 41 years to 1980. However, I am fairly sure I have seen R-Cores in modern McIntosh Labs audio equipment pictures. Were they for the output transformer use, or for power transformer use ? I do not know! If I recall properly, I seem to think seeing a total of three R-Cores in a single McIntosh chassis.

I know for a fact - that a small high end audio Manufacturer , Dennis Fraker of Serious Stereo in the USA, uses Softone R-Cores. He told me, this week, that " this is all he plans to use, going forward." In my experience and personal opinion, he consistently hand-builds the world's best sounding 2A3 and KT150 SE amps, directly coupled, since 1989.
 

IndianEars

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I spent Quite sometime Googling for McIntosh using R Core Output transformers... Did not find any such reference of picture on the net.

I ofcourse do not rule it out. If you do however fid a specific reference, do share.

Incidentally, Shilchar Electronics, India is one of the Handful of R Core Transformer (5VA to 1500VA ) manufacturing companies worldwide.

 

drlowmu

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Any particular reason that you posted this circuit diagram ?

Its a fairly typical typical & straightforward implementation of a 2A3 SET ...


Yes, I posted it......... because it is called a " RW 2A3." Did any one catch that, from someone from Japan?? A "Roftin"-White 2A3. Not a Loftin-White . It's related, ( a first cousin ), to Mackintosh.

That Shishido 2A3 circuit, as I pointed out, needs many improvements, and should not be copied by any DIYer as it is.

Here is the latest update on the 6005 Stereo SE amplifier :

As of this morning, I am listening to the two most sensitive B+ spots in the entire amp ( the B+ for the Driver tube's plate resistor ( Ra ) and now, the B+ for the output tube's G2 ), with each sensitive area having it's own separate quadruple filtered B+ supply.

The playback precision of musical instruments today, is breathtaking to hear. I am, as-of-now, very "sure" of this newest power supply design and configuration. It is 100% desirable to have extra-ordinary B+ filtering. I am hearing all of this, on playback.

B+ feeds need to be super clean, especially when both channels are operated from a single supply. Great care has been applied, to execute this new 6005 stereo amp this way. No one ever has done this before in audio, for the Ra and G2 both. The quadruple filter to each location has this configuration :

L1/C1...........L2/C2.............Shunt 1...............Shunt 2.

The Ls ( chokes ) referred to above are small - "hash" chokes, the size and shape of a 2 Watt resistor. These hash chokes are maybe 1 Ohm in DCR , and 500 mA. capable, 100 uHY or less in inductance, single layer wound. Very useful, and seldom seen.
 

Hari Iyer

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Jeff, Will you use shunt 2 on a monoblock too? This being a stereo amplifier the power supplies are shared between 2 channels.
 

IndianEars

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For decades, the importance of carefully regulating the B+ supplies has been ventilated.

Alan Wright (actively) regulated the B+ with ripple down to the milli-volt level.

I believe VTL also uses stiff, actively regulated B+ supplies.
 

Hari Iyer

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IndianEars, i don't think regulating the B+ supplies to mV level has any sonic advantages. No doubt it could reduce some "hum" though. It depends how the regulation of the B+ is achieved - high value chokes / high value capacitor or an active device. I would rather use a low value choke/ capacitor and have better dynamic response to music impulses than worry about small amount of ripple.
 

drlowmu

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Jeff, Will you use shunt 2 on a monoblock too? This being a stereo amplifier the power supplies are shared between 2 channels.


Hari,

In the future, I will double shunt G2 ( and the Ra's B+) if that is the question you are asking me. On a monoblock, one has room to do this. I will also always double L/C ( using hash choke Ls ) G2 and the Ra, from now on, in any monoblock and/or stereo amp.

On a stereo amp that is built for high performance ( why do it any other way ? ), this " quadruple " topology must be done in my opinion today, due to the shared supply. I have listened all day off and on to quad filtering of the Ra and of G2, and frankly from what I am hearing of my reference music selections, I "must" now have an amp done this way. The inner detail of the double shunting, combined with the "quietness" of a double hash choke L/C, is hard to not to have as part of a high performance amplifier design, once heard.

I am now hearing what I want to hear, performance-wise, from the power supply configuration of the new 6005 amplifier. It is superb actually. There is a lot of work ahead of me. I will design a bigger chassis, and put the parts you saw in this amp, in a finished chassis with less crowding, a big rebuild. I also have a lot of work to do, to experiment and find the right combinations of multiple film cap bypassing, so the amp plays a large variety of musical instruments properly.

Over the last three weeks, I have methodically determined and optimized the driver tubes' ( higher ) operating voltages, and as of today, fully determined the amp's overall needed power supply. Achieving both of these optimizations, is very satisfactory to me - having accomplished both makes me happy. The remaining work is to design and carefully lay out a new larger chassis, and experiment with multiple film cap bypassing, to make the most of things.
 
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drlowmu

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IndianEars, i don't think regulating the B+ supplies to mV level has any sonic advantages. No doubt it could reduce some "hum" though. It depends how the regulation of the B+ is achieved - high value chokes / high value capacitor or an active device. I would rather use a low value choke/ capacitor and have better dynamic response to music impulses than worry about small amount of ripple.


Hari,

That is a brilliant response. I understand from often repeated direct experiences, what you are saying. Others may not !!

Probably, only 2-3% of all power amp designs are regulated. A form of passive regulation, the way we two might execute it, will outperform active regulation, on the basis of our passive methods being far more dynamic, and having less noise, from the ( often used ) solid state parts in an active regulator.
 

IndianEars

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Hari & drlowmu.... I agree to disagree... :)

Hari, Regulation is Not only to do with ripple.... It changes the sound character... Not only with Glass Audio, but also with Silicon ....
 

Hari Iyer

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Shunt regulation works quite well as passive regulators though at expense of heat, but has advantages of lower noise IME. I have tried lowering ripple a bit by added extra capacitors. Each time I did that, I lost dynamic response and the music sounded more sterile and lifeless to my ears.
 

IndianEars

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Interesting observation, Hari.

We also need to keep in mind that shunt filteration n shunt regulation are different matters
 

Hari Iyer

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Hash chokes + capacitors are used for shunt filtration and Resistor + capacitor for shunt regulation
 

drlowmu

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Hash chokes + capacitors are used for shunt filtration and Resistor + capacitor for shunt regulation
In the strictest sense, we might say a shunt is not a regulator.

But who cares, the real point is, Hari, you and I use it, and to great effect.

It is rarely seen, in the schematics I preview.

A design may use a shunt R, to " bleed / discharge the capacitors " for safety reasons upon turn-off, but it is very very seldom used to improve the sonics of an amplifier one would seriously listen to. As far as I can tell, only Thomas Meyer ( of Germany ) uses an very mild shunt, maybe 1/4th the value of what we do, and I do not recall seeing it anywhere else. (1)

Yes, the double hash chokes and small film caps ( L1/C1, L2/C2 ) helps to remove power supply B+ noise. It keeps this unwanted noise from polluting any of the most sensitive stages in an amplifier. It removes " the frizzies ", or unwanted artifacts, and it stabilizes the B+ supply a bit.

In all my years of audio and amp building, I have never heard the listening result one can obtain ( in 2021 ), by double ( series ) hash choke filtering combined with double series shunting, of a tube amp's sensitive B+ rail. This effective technique is presently used and exclusive to only two people I am aware of. All others it seems, in the vast audio world, are oblivious to this.

Enjoy your amps Hari !! " The proof of the pudding " is in the eating .

drlowmu

(1) Correction, one exception I recall. The 22K 3 watt resistor in Nobu Shishido's "RW" 2A3 DC amp acts as a mild SHUNT, of sorts, and that amp's full schematic is on this page .
 
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IndianEars

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Yes, drlowmu... as you admit, a shunt resistor is Not a regulator....

A (voltage) regulator has a mechanism to Maintain a constant output voltage when the Input voltage changes.

A regulator - Shunt or Series will Always have an 'active' element who's characteristics change with the voltage ...

A Zener is a good example of a regulator that is typically used as a Shunt Regulator.
 
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