As the principal designer of the amplifier, I am joining the forum and making myself available to answer questions and when the spirit moves me, to generally talk about various things audio.
1 Like
Howdy Bascom
These are a friendly bunch of people, that also hold your feet to the fire at times 
Welcome, Bascom!
I am truly delighted you are joining us. This is a treat!
BHK said As the principal designer of the amplifier, I am joining the forum and making myself available to answer questions and when the spirit moves me, to generally talk about various things audio.Welcome, welcome. Let me starts with a question right of the bet. If you had to put the new amp side by side with any amp you're familiar with, which amp would be closest in overall sound quality and sonic signature?
Welcome Bascom
Can you talk about the overall philosophy and design of the PS in the new amp
thanks
Welcome Bascom!!
Bascom’s a little new to the forums business. I’ll help him get going and assume the rest of you will assist as well. This is terrific. A real first.
I will do anything I can to help. Just let me know if there is anything I can do. This is exciting.
Bascom’s work is silly good. 
Wonderful to have you here Bascom! I’m really looking forward to the dialog (and getting my hands on one of these beasts).
Welcome Bascom! Paul has been very generous over the years with sharing his philosophy and it will be interesting to compare your philosophy to his. Being more specific, I would certainly be interested in hearing your thoughts on how you approach each amplifier design. I would think someone working for a single company for a number of years would have a more homogenous approach to design (of direct interest, Paul’s use of only solid state devices), but you have worked for a number of companies over your career and wonder how that enters into your design philosophy. Do you always aim for what you consider the best, period? Or do you enter into a design with certain goals that change by who you are working with? More specifically, did you have something special in mind with your PS Audio effort? I’m sure everyone here will have other things to ask, but this seems a good start. Thanks for your participation!
Hi Bascom
Thanks for inviting me to this place, probably my first posting here as well Be welcome here on the forum, I am sure you will do a good job!
But now i will finish your music server setup… 
Best,
Phil
Welcome, Phil!
This is my first answer to a poster, I will have more to say as this all proceeds.pmotz said Welcome Bascom! Paul has been very generous over the years with sharing his philosophy and it will be interesting to compare your philosophy to his. Being more specific, I would certainly be interested in hearing your thoughts on how you approach each amplifier design. I would think someone working for a single company for a number of years would have a more homogenous approach to design (of direct interest, Paul's use of only solid state devices), but you have worked for a number of companies over your career and wonder how that enters into your design philosophy. Do you always aim for what you consider the best, period? Or do you enter into a design with certain goals that change by who you are working with? More specifically, did you have something special in mind with your PS Audio effort? I'm sure everyone here will have other things to ask, but this seems a good start. Thanks for your participation!
Interesting questions. I always want whatever I design to sound as good and realistic as possible regardless of who I design it for. In the case of the BHK Signature 250 amp, I had an opportunity to build on past information that I had learned in recent years. One thing I learned is that the circuit topology of driving the same sex output devices with a preceding differential amplifier was a good one. Yamaha had used something like this way back in their B1 power amplifier. I had learned of that topology way back with a Spectra Sonics 110 card for mixing consoles. My friend Geoff Cook turned me on to this circuit. It used bipolar transistors but could be used with other kind of devices like MOSFETs. Anyway, I had the idea a couple of years ago to use this topology with all MOSFET devices and it really worked out great sonically. I built a headphone amp with this idea with a dual triode as the input differential amplifier. This first stage was included in an overall feedback look and really sounded very good. Subsequent study of a number of good headphone amplifiers including one by Pathos, the Aurium, which I bought because it was so good, used a dual triode by itself not included in any overall feedback loop and was followed by MOSFET outputs, one as a follower with a constant current source. So to the BHK Signature 250 amp, I was inspired by my good friend and associate, Arnold Nudell to design a power amp with this differential tube input stage followed by an all MOSFET output amplifier and that is largely what the BHK Signature 250 amp is. To answer another person indirectly on this forum who asked what other good amps have I heard that this one sounds like, I honestly have to say that no other that I have had in my own system has sounded this good or like it. The production prototype truly sounds outstanding and I am sure that anyone that buys one is going to mighty happy with it!
BHK said So to the BHK Signature 250 amp, I was inspired by my good friend and associate, Arnold Nudell to design a power amp with this differential tube input stage followed by an all MOSFET output amplifier and that is largely what the PS Audio power amp is.Why a tube input? I like tubes, but am curious what this input does that a solid state circuit would do differently.
BHK editing this post to respond here - From an intellectual and measurement standpoint, the tubes don’t really do anything different from solid state devices in the same circuit. BUT and it is a big but, all things considered, the tubes simply sound more like the real thing. And this is especially so in the BHK Signature 250 amp design.
AudioPhil said Hi BascomThanks for inviting me to this place, probably my first posting here as well
Be welcome here on the forum, I am sure you will do a good job!
But now i will finish your music server setup…
Best,
Phil
Hey Phil Welcome you have plenty of friends here was are big fans of AO
Elk said Welcome, Phil!
magicknow saidAudioPhil said Hi BascomThanks for inviting me to this place, probably my first posting here as well
But now i will finish your music server setup…
Best,
Phil
Hey Phil Welcome you have plenty of friends here was are big fans of AO
Thanks both to you!
And I welcome you as well Phil and Bascom! Thanks for participating and sharing on the forum. Do understand that while this is a PS Audio forum we work hard to keep it open, free and informative. If the discussion drift to subjects not PS Audio, that’s fine and, in fact, encouraged! It isn’t a sales tool for us, it’s a sharing tool, one we want our friends and readers to enjoy and learn from wherever it takes us. We wish to have a place of gathering where we all feel welcome and free to speak of all things audio, music, even humor.
Carry on!
Elk saidI shall, of course, wait for Bascom to answer, but in the meantime I share at least my reason. It just sounded better. And it took some doing to convince me, but Bascom and Arnie were quite sure it was the right course.BHK said So to the BHK Signature 250 amp, I was inspired by my good friend and associate, Arnold Nudell to design a power amp with this differential tube input stage followed by an all MOSFET output amplifier and that is largely what the PS Audio power amp is.Why a tube input? I like tubes, but am curious what this input does that a solid state circuit would do differently.
So afraid of this path was I, that we spent a great deal of time coming up with an alternative. Bascom will recall that I asked him to design us an alternate FET version of the input stage. He did and Bob Stadtherr, our chief engineer, spent his days building a few different versions of it mounted to a tube socket, complete with tiny heat sink and PCB to accommodate. This made it easy to exchange inputs and listen to the results. At the time we did this all I had available was a 6229 tube set we had laying around (I think Bob ordered them from some of his suppliers). The experiment didn’t take too long. Within the first few moments of but one track of music I could hear the magic removed from the amp. It was rather startling actually. I went back and forth on numerous tracks, the differences always the same: a cardboard-like presentation of the music vs. open, lush, real with the tube. And that particular 6229 was the worst of the lot.
Our original plan was to ship each amp with the FET installed, and make it easy for owners to then swap in their choice of tubes, thus always having a solid state backup available. Those plans were scuttled on that day. Shipping the BHK Signature with anything less than a tube would be criminal and never represent that that has turned into the most magical and music sounding amplifier I have ever had the privilege to listen to.
But that’s just my take.
This is not just the ‘PS Audio amplifier’, it’s the BHK Signature. So named for a very good reason.
Paul, with all due respect I’ve never heard of a 6229 tube - is it possible you meant a 6922? (The 6922 is a 6DJ8 tube type equivalent to the European ECC88 / E88CC tube and can be used in any 6922, 6DJ8 or ECC88 circuit.) Thanks!
Bascom King stepping in here - I didn’t see the misquote yet but indeed the BHK Signature 250 amp is to shipped with Genelex Gold Lion 6922 tubes. As a matter of interest, perhaps someome can tell me how to respond to a particular post. I haven’t seen any obvious way to reply to them so I tried this.
I’m sure it’s a typo. I think I read somewhere it will ship with Genelex Gold Lion 6922s.
+1
A simple typo.
My understanding is that a lightly driven triode is very linear. If correct, this may be part of the magic.
What intrigues me is that Paul is not seduced by euphonic tube sound. I am certain the amp is not coloring the sound in any fashion whatsoever. Thus, what does a tube do in the context of this amp that solid state does not?
(I have been gently tempted to buy one of the plug-in SS replacements for a tube just to play with it. But aesthetically I just could not due it.)