" Jeff's High Performance SET Amplifier "

Discussion in 'Tube Gear' started by dowto1000, Sep 15, 2017.

  1. dowto1000

    dowto1000 Junior Member

    If anyone read my introductory post on this lovely Forum, I was NOT luke-warm, but stated very clearly what I had found in audio.

    I said the following :

    I like to design and build my own SET DC two-stage triode amps, because I think amps, and not speakers, are the WORST performers in audio. I feel 99.99 percent of the available audio amps are SORELY lacking, in many many areas. A travesty !! So, since I can't afford the best amp I am aware of, ( especially for ALTECs, the Serious Stereo amp ), I do my own builds.

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

    Of course, as soon as I write " I think that 99.99 percent of the amps are unsatisfactory ", I have just ALIENATED myself to ANYONE who reads my post, and has carefully, thoughtfully paid their money for whatever amp they own.

    I have been this way for over three decades, about audio amps.

    It is one thing to criticize, but, HOW ABOUT, for once, finally offering an affordable-to-build POSITIVE solution.?

    I know, many will not ever get to listen to, and / or be able to afford " the best amp " I know of, for speakers 98 dB and above ( The Serious Stereo amps.)

    SO, while I can not ethically share what is inside that amp, it is proprietary, I think NOW is a good time for me to STOP complaining about everyone else's sorry tube amp designs, and offer an EASY and inexpensive DIY build, that I designed 9-11-17

    I think I will name it simply " Jeff's High Performance SET Amp ". Never before, has a total SET amp design, that I find suitable, ever been made public on the WWW.

    The amp has only been designed on paper, but I have done such work as this, designing triode amps " from scratch ", since 1982, and Directly Coupled two-stage triode amps, ( my favorite sounding, highest performing topology ), for the last dozen years. I AM NOT LUKE-WARM ON THIS TOPOLOGY, I EAT, BREATHE AND SLEEP IT .

    No one has yet built this, but it is probable, that a Senior Member of this Forum may do so, and report to us all, about his own build, and give us own listening comparison to his conventionally-designed ( "mis" designed according to me ) 2A3 amps, on his ALTEC 604 speakers.

    For now, I will just post the schematic, wiring diagram, and my PSUD simulations of the power supply.

    Comment, : In any two stage direct coupled tube amp, ALL the voltages are interdependent on each other, and it is good when all the voltages balance. After posting this, LOL, I see a 1 VDC error, ( 334.25 vs: 335.25 VDC in PSUD ) and I will re-post corrected PSUD and a corrected schematics, within 24 hours. It won't take much, or change much, to fix this, just a value and parts change for R5.

    Again, I am open to any and all questions. Perhaps this will develop into an interesting and informative thread. I am confident this design, both performance and reliability wise, will be " da bomb" hence my amp's appropriate name " Jeff's High Performance SET Amp ".

    Lets have some FUN with this .


    CAVEAT : A person MUST have 98 dB or higher speakers, and they must be properly implemented, ( mainly in the amplifier-to-speaker wiring technique ), to even begin to remotely hear what this design can fully do. I am happy to lay-out what sort of amp to speaker wiring I find great, separately from this DIY SET amplifier build thread. I truly hope, some of you readers enjoy this. Thanks.

    Attached Files:

    Last edited: Oct 16, 2017
  2. Punker X

    Punker X Junior Member

    Personally I think your attitude needs to get in line with this forum or take a hike... Way to confrontational. Last time I checked this site was not about who's or what sounded the best. Fine to claim what you like.. Keep the disrespecting of what other people like to yourself or move on. Plenty of other places on the try and prove you're correct.
    4-2-7 likes this.
  3. dowto1000

    dowto1000 Junior Member

    The topic of this thread is a high performance SET audio amplifier design for speakers 98 dB on up, and not your perceptions of me..

    Early - on, I posed a huge problem in audio, under-performing audio amplifiers, and I have provided herein, for the first time in the public domain, a wonderful solution to the problem.

    For FREE, I have offered a design that can be very reasonably built. In my opinion, this KISS design on efficient speakers, will easily out-perform 99 percent of all amps anyone can own, or that people have ever heard.

    Lets stay with the topic, a new, high performance tube amp for efficient speakers.

    BTW, I still need to correct R5 slightly, a couple hundred Ohms. Within 48 hours as it looks at the moment, I will re-work and re-post the data. The correct operating voltages, tube and resistor dissipations, the GIST of the audio amplifier is all there now - offered in my initial post .

    Questions anyone??

    Thank you,

  4. dowto1000

    dowto1000 Junior Member

    Corrected R5 Schematics, corrected PSUD2 Simulations, everything denoted as REVISION 5.

    Thanks, its OK now. DIY it !!

    5K output trannie. First choice, Softone RW-20. Look it up ! :-)



    Attached Files:

  5. Mister Pig

    Mister Pig Active Member


    I think I left a truffle around here somewhere.

    Far more interesting to me than another Savior.

    Mister Pig
    4-2-7 likes this.
  6. TubeHiFiNut

    TubeHiFiNut Administrator

    Jeff.....PLEASE just offer the schematic and state that this is what you like to listen to.

    By coming on so strong, you drive people away from even considering your point of view.

    This is not the way to win friends and influence people - for you or for Serious.
    4-2-7 likes this.
  7. Kyle

    Kyle Junior Member

    Hi Jeff,
    I have a technical/subjective question; Why a 12at7? I have used them, I've also heard a number of people say they're harsh sounding and unreliable. I've not had those issues but they're not the best sounding driver for whatever reason. I'm sure you auditioned several drivers before you made the decision.
  8. dowto1000

    dowto1000 Junior Member

    Hello Kyle ,

    Nice to hear from you. The 12AT7, or any other good quality tube, is capable of outstanding performance, if you know how to implement it.

    A good engineer, will choose the tube type he needs, and GET the performance he wants. One fine example : Audio Research has used MANY different tube types over the years, and they eventually GOT the performance they wanted.

    Beyond the 12AT7 question, there are FAR BIGGER issues, that I have overlooked, in trying to design a Direct Coupled amp with a INdirectly heated Finals tube ( 6AQ5 ).

    I was designing this amp on 9-11-17 as though it was a DIRECTLY heated tube ( 2A3 or a Type 45 ). I have only been direct coupling with directly heated tubes, the last dozen years . NO "separate" cathode sleeves ( 6AQ5 ) were ever involved.

    The NON engineer in me, overlooked some VERY important things, and the bottom line is, I want to WITHDRAW the direct coupled recommendation I have boldly made here ( above ) in this thread, , and NOT DIRECT COUPLE into a 6AQ5. SO, THIS is to " be continued, " sometime next week or ???.

    I LIKE the sonics of a 6AQ5, and I absolutely LOVE the sonics of the power supply filters I have suggested.. Employing a pair of 6 Ohm DCR chokes instead of two 10 Ohms chokes in series, is simply lovely to my ears - and a "must-have" level of performance under hard drive - in my home's system. ( Well-wired VOTT A7-800s ).

    But Kyle, an indirectly heated tube ( for the Final tube in a direct couple ) has different design considerations, that I goofed up on, and DID NOT consider AT ALL, until tonight !!! .

    Technically, I overlooked the indirectly heated tube's maximum breakdown voltages to the cathode, from the plate to the cathode, and from the cathode sleeve to ground. All of this, is to AVOID stripping the cathode. I also needed to consider the grid' s maximum breakdown voltage to the cathode sleeve also. These are "INdirectly heated tube issues", .....I simply overlooked."

    I'll make up my mind, on what to do, next week I suppose. Thanks , and I apologize for unintentionally misleading anyone .

    Last edited: Oct 16, 2017
  9. Richard Austen

    Richard Austen Junior Member

    I've been on forums for a long long time and the only problem you have at present is simply that it's only you who can make and substantiate your claim. There was a DIY guy on audioasylum who told everyone that all their speakers stunk but his modified Bose 901 was the best speaker ever. And you know what? It may be - but no one can verify it because no one can go out and listen to and compare it to anything.

    As a reviewer - the only thing I can do is to review something that exists as a retail product (or as a kit) and compare those items.

    I have a small bit of advice to anyone who thinks they think they have invented something new and sounds better - BUT - don't have the money to get the product out into the masses by forming their own company - go and send a finished product to a major SET manufacturer and let them compare it to their units and if it is good they may well hire you to be on their design team and probably pay you more than what you're making now.

    I know Audio Note has done this very thing. They are arguably THE major player in the SET world designing new original designs (patented) and have taken some big engineers from other companies. They are quite big and have been contemplating buying other major brands they like. And you have to try and take your opinion out of it and see what critics and dealers think about it. Remember that lot's of people like SS over SET, as baffling as that may be to you or me.

    Lastly, I have spoken to a number of manufacturers and many of them genuinely believe what they do is the correct path and the best sounding path. In other words they think what they sell is the best stuff. The difference is they put themselves on the line - some will agree and some will not. No matter how good it may be on the measurement plot or which appeal to authority one can make.

    I own the same speakers that Steve Hoffman has - Hoffman mastered and or recorded numerous big name artists from the Beatles, Miles Davis, Eva Cassidy, Ella Fitzgerald, Pink Floyd, the Eagles, and on it goes. I trust his ear but he prefers the 300B to the 2a3 I prefer the latter to the former. So while we're very close on things - there is mild disagreement somewhere along the line. There is no one size fits all solution - even if everyone has 98dB sensitive speakers. An example of this strong opinion is Peter Qvortrup's belief that everything in the system chain should be designed as a complete system over individual components designed by different engineers with varying abilities. The Notion that synergy can be more than the sum of their parts. And logically it is very sound - mix and match systems tend to be a series of tone controls. You can see his interview with enjoythemusic.com's founder/publisher/editor Steven Rochlin


  10. Richard Austen

    Richard Austen Junior Member

    I can only make one show per year and that was the California Audio Show in Oakland. I should be able to attend next year as well. My full time job is as a teacher in Hong Kong and unlike Canadian and US teachers I get 5 weeks vacation not 11-12 weeks (although I get paid for my vacation unlike them). I quite liked the California Audio Show because the hotel's room construction was the best I've been to, which allowed for above average sound from all demonstrators. Still hotels and audio shows are not the best way to judge quality of rooms or systems. As an Audio Note speaker owner I can tell you that they can sound rather weak at one place and brilliant in another. This is especially true for speakers that are corner loaded as the walls become integral to the result you are going to get. MBL omni-directionals also suffer depending on the rooms. That's before getting into what amps and sources are doing.

    At CAS7 - three of the four best sounding rooms all used non oversampling CD replay - they beat every room using computer audio as the source. Vinyl and R2R tape were even better. The source IMO is more important than power amps. Indeed the best overall sound at the show IMO was from a solid state amplifier and I am not a solid state fan! I learned later it was a $100,000 SS amplifier so maybe they do something magical in the design room but that's way out of my budget and for $100k it should beat some tube and SET amps for $2,500 :) The speaker was a horn too. A horn I would buy if I had the money. Low sensitive for a horn at 91dB.
  11. dowto1000

    dowto1000 Junior Member

    This corrects errors I made, in this thread's original #1 and #5 posts.

    I am trying to offer audio enthusiasts, specifically all of us listening to 98 dB and greater efficient speakers, a high-performance audio amp design, that I feel is worthy.

    The design detailed here below, derives from the 1929 Loftin White two stage direct coupled amp, and it has elements of two prior documented amps ( Isamu Asano 's DC 2A3 amp, schematic attached, and the Ciro Marzio - Christiano Jelasi DC amp ), with thoroughly - tested and very specific new design suggestions, I offer.

    There is very little information found on the Asano amp, but the Marzio-Jelasi amp was nicely presented in Sound Practices magazine, Issue Six, Spring - 1994. That article, minus the authors' names, can be accessed here :

    ( http://www.ispra.net/audio/DCSingleE...fier/index.php) .

    As a KEY part of my recommendation, I am suggesting the precise use of Marzio and Jelasi's film capacitor BYPASS VALUES, ( 0.22 and 0.022 uF ) " everywhere in this SET amp " just as the Italians determined, through their own careful listening tests.

    However, my film capacitor TYPES differ. I advise using today's latest and higher-performing film caps, easily available to us all, thankfully at INDUSTRIAL prices. .

    I fully concur with what the Italian fellows heard., and determined by ear... their bypass cap uF VALUE choices.

    It is PRECISELY their film cap bypasses, ( for EVERY capacitor position, of a SET amplifier ), that uniquely turns their SET amp and this amp, into a SET with a wide-band response, ie: it plays the mids and particularly the highs better.

    The 0.22 uF bypass value, in a WIMA FKP1, enhances the midrange, and the 0.022 uF bypass value in a WIMA FKP1 effects the high frequencies, positively.

    My own changes to these prior two DC designs is to employ extremely linear tubes, using conservative operating points, so the amplifier is long-term reliable. My design choices, carefully made, avoid degrading of the tubes (1) - and avoid a degrade, over time, of high-performance playback. . Also, I am presenting a FAR better power supply, unconventional, which I really enjoy hearing,. something thoughtfully evolved over the past 35 years.

    This power supply features low DCR inductors, and smaller-than-usual ALL film capacitors, so that the tube circuit can nimbly respond, with fullest dynamic contrasting, to the transient nature of music. The TOTAL DC resistance ( DCR ) of my B+ filter chain to the Finals' tubes, after the rectifier, is only 12 Ohms !! ( 6 Ohms plus 6 Ohms ).

    Compare that with the series resistances of 99.9 percent of the tube amps that exist, especially the ones sadly saddled with the "dumbest part people regularly / thoughtlessly use" in a power supply to the Output stage, a 10 HY / 100 Ohm DCR Inductor / music-robber.

    Question : What B+ filtering system transfers energy better, quicker, on music's demands, 100 Ohms of series resistances to the critical Finals' stage, or 12 Ohms ???

    In multiple ways, my SET DIY design ( schematic below ) uniquely-in-audio, maintains MAXIMUM TRANSFER EFFICIENCY of ENERGY, through the amp, to power the speaker. One example of superior , thoughtful optimization involves Hammond's 159ZA, which is a six Ohm 1 Ampere-rated inductor. It comes stock with 22 AWG leads. 22 AWG !! LOL - Goodness ! Such stock leads are removed and upgraded - replaced with wide band high-quality 14 AWG Mil Spec wire, made of pure copper and silver, teflon insulated.

    In addition to the power supply inductors, leads are likewise re-worked for the power transformer ( primary and secondary ) and for both the stereo amp's Type 46 filament transformers. No filament hum pots exist either, with their inherent losses.

    I am confident this Direct Coupled SET amplifier will be a ton of FUN to hear, based on recent listening sessions with a similar Type 46 stereo amp.

    To obtain both high performance and reliability, it is imperative that NO parts or value substitutions be made, what so ever. Layout, and wire-dress is also critical . I am usually available publicly and privately, to assist DIY builders, etc.. If anyone has questions, especially good questions that might be helpful to other readers, fire away !!

    Thanks !! for visiting this thread. This is "THE" highest performing DIY SET schematic and chassis lay-out I have ever seen, in decades of viewing SET amplifier schematics. The audio circuit can be used verbatim, with the lesser-performing Type 45 tube, or, scaled-up to a JJ 2A3-40 Finals tube.



    Type 46 Finals tubes herein are each operated at 6.08 Watts dissipation, about 61% of its 10 Watt maximum, so, on purpose, dissipation approximates the Golden Ratio proportion, 62% .

    This provides a much longer tube life. Additionally, tubes conservatively operated never exhibit the thermally STRESSED sound I hear, when they operate at, near, or even above their maximum ratings, ( as many sadly and needlessly do ). Such other amps tubes may HAVE to be hot rodded, to get the amp to sound somewhat decent, on a temporary basis before they self-degrade. To me, this hot rodding is a common and inferior design trade-off.

    So, .. what MATCHES very WELL with amps that do not hot rod their tubes' plate dissipation? Answer : a MAXIMUM TRANSFER EFFICIENCY of ENERGY amp design and implementation .

    All of this I suggest is blatantly audible, when one does amp design work, using 100 dB plus speakers ( I use hybrid ALTEC A5 / 800s ), well-wired, and a good source. This amp, built with NO changes, ( IMHO ) will very EASILY out-perform 98 % of ALL amp designs, past and present, on 98 dB and higher speakers.

    Have fun.

    Attached Files:

    Last edited: Oct 16, 2017
  12. dowto1000

    dowto1000 Junior Member

    Been asked about Layout.

    In SET amps, layout is ULTRA-important, and so, the attached should be copied precisely.

    This layout can conceptually be used with any stereo DHT Finals implementation.

    It is superior, IMHO, in parts positioning to any DHT stereo amp I have ever done or ever seen before.


    Attached Files:

    Last edited: Nov 14, 2017
  13. dowto1000

    dowto1000 Junior Member


    Wanted to update this specific thread.

    By October 30, 2017, I had determined, for the first time, that Type 46 directly heated tubes are not as desirable as I had originally thought they were.

    So, to not mislead anyone, who may copy / build from the schematic I'd posted ( of the Type 46 amp in this thread ), I wanted to conclude this thread by saying

    " I no longer can recommend the Type 46. "

    SEE this :


    In its place, I would unreservedly suggest people with 98 db and higher speakers build with a JJ 2A3-40, a simpler and REAL triode tube, as being the very best possible tube choice I 'd can suggest, on a cost versus performance basis. This is what I will do henceforth.

    The circuit I showed is fine, it just needs to be adapted to the JJ 2A3-40's operating points.

    Thank you and regards,

    Last edited: Nov 14, 2017
  14. 4-2-7

    4-2-7 Junior Member

    So this .1% awesome amp now sits in the junk pile of 99.99% of all other amps ever made.

    Ok got it, can't wait for you new design so I can listen to music properly.
  15. inthewoods

    inthewoods Active Member

    May as well listen to 300B's. Didn't care for the 2a3-40's. Colored my music. Gave them away.
  16. dowto1000

    dowto1000 Junior Member

    OK. Its not necessarily a tube problem, but rather, how a person implements the tube in a circuit, the circuit itself, and all of the associated parts choices.

    I am a big 2A3 fan, and my two favorites have been the EML Mesh Plate and the JJ 2A3-40.

    So...what ARE you using as a finals tube now, and what sorta speaker ?? What circuit in the amp ?

  17. dowto1000

    dowto1000 Junior Member

    No, not in the junk pile. I like the circuit ( two stage, direct coupled ) it is in, very very much. That basic circuit, and my wire and parts choices, stays !!!!

    I will just adapt it - change it from Type 46 Finals to JJ 2A3-40 finals, after my friend uses it as his 46 amp for awhile. Both tubes use 2.5 VAC filaments, so its just plate and cathode resistor changes here and there, easy for me to compute, execute.

  18. TubeHiFiNut

    TubeHiFiNut Administrator

    Just want to confirm my understanding.

    If someone wants to build a 2a3 amp that encompasses your design theory and implementation protocols:

    1) use the 46 amp schematic in this thread.
    2) change the plate and cathode resistors to use 2a3 tubes.
    3) Use the layout diagram in this thread.

    Anything else that needs to be done?

    Specific parts list?

    Thank you, Jeff.
  19. Redboy

    Redboy Active Member

    Interesting point. The flipside of this coin is that maybe the 46 is a perfectly suitable tube, and your implementation or your circuit is the problem...

    It's possible. It's good to keep an open mind about these things.
    Audionut and Don C like this.
  20. inthewoods

    inthewoods Active Member

    I used the JJ's in a Bottlehead Stereomour. Currently using RCA's in some monoblocks. haven't a clue as what circuit. Speakers are OB.

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