Does anyone care to ask an amplifier designer a technical question? My door is open.


I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.

I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
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Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.

I like to tell true stories of my experience with others in this industry.

I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.

On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.

I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.

Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.


Fe8c8cab 4117 4c51 b1aa 6b134ad0dca6ramtubes
Hi to all. 

Perhaps I was not clear in my original posting that this is a thread to ask the OP a question and have it answered by the OP. It was not an open invitation for other designers to answer questions or give their opinions on my answers. The whole point is to give the public some insight on how I design things and how I evaluate my own and other equipment. 

If you notice John Atkinson and I have similar views on what an amplifier ought to do.

If other designers want to have such a thread all the better. I would not care to comment on their thread because those are their answers, their views. 

In the end I hope to educate. As far as selling anything I am happy to share the workings of my A/B test set up for no charge or build one for someone if they want to get into A/B testing. 

I am most happy to discuss interactions in equipment, how I go about designing, how I listen. Far down the list is the sound of particular tubes or brands of the same tube. I will talk about what different tubes can and cannot do well. I can talk about how some circuits are more sensitive to tube rolling and some are much less so.  

Now can we please proceed with this in mind.

Well, it turns out that it was my friend Ralph (we have never met, I simply call him my friend) who misspelled Charley's name.  
It is in no way an excuse for bad specs- and in fact our amps have some pretty good specs (if proper measurement technique is used, which means **don’t ground a speaker terminal during testing**, which is the mistake that almost everyone except Charles Hanson made/makes). I suspect you didn’t read the paper at the link very carefully, since you claimed that you read it, yet still with the remonstrations!
Sorry. Now back to my sorely missed idol, the great Charles Hansen. He gave an interview to S'Phile back in October 2016 (or at least, published in that issue) and said this; 

I didn't really understand it for a long time. When I first made the Ayre MX-R amps and KX-R preamp, I thought, Okay we've done it. We've made stuff that is so good it's as good as tubes—why would you bother with tubes? But I would still get customers and manufacturers who would say, "Yeah, that's nice, but I'm still sticking with my tube piece, because you haven't got there yet." And one of my weaknesses, for better or worse, is that I have such a big ego, I don't have to listen to other kit. I just listen to my own designs. If I had, I would have known what they were talking about.

When we made the KX-R Twenty, we took all our ideas we had been working on for 20 years, and getting feedback from people who were able to teach me how to listen better, and what to listen for—20 years of hard work. And then I hooked up the KX-R Twenty and I went, "Holy cow! This is what they were talking about. No wonder they didn't want to listen to solid-state—this is what they wanted to hear." It just hit me: This is what all those tube nuts were talking about. I would send stuff off to these dyed-in-the-wool tube guys, and they would say, "Nope, it's gotta have a tube in it or it's never going to work right. No, it's just sand. How can it sound right?"


Read more at https://www.stereophile.com/content/charley-hansen-wizard-boulder#1xppIjoxr0TfgdJG.99
My point being that here we have this great engineer who thought he had engineered a product that tested well and sounded great and then he had an epiphany of sorts that something better was indeed out there and attainable. I continue to believe that old maxim that we're all tired of reciting let alone hearing; not all things that matter are amenable to testing. 
In a separate post your "intake guy" Clio-something really gave me the business about being a troll and not having anything technical to add. He's kind of right and kind of wrong IMHO. I may not have technical expertise but I will never believe that JA's measurements trump listening impressions. Roger-the Roger that I have metaphysically shaken hands with-enthusiastically too-you have endorsed JA's measurement techniques again and again and yet the fact of the matter is that JA has never given any tubed amp an enthusiastic endorsement from the standpoint of measurements. If your amp is an exception, than fine, that would be one instance of my "never" being incorrect. He may have given that monster hybrid integrated by Musical Fidelity-a known S'Phile darling-a thumbs up from a measurement perspective as well. So that would be two exceptions. 
Btw, go back to the full link of Charley Hansen's interview and see what he said about finding a power cord laying against the carpet at a show and finding that one wood block cured his perceived dissonance. What do you have to say about that? That it was in his mind? 
Well, it turns out that it was my friend Ralph (we have never met, I simply call him my friend) who misspelled Charley's name.  
He did the measurements of our old M-60 kit for Glass Audio. I met him and hung out back when he was still Avalon Loudspeakers. Different world... nice guy. He is missed.
In a separate post your "intake guy" Clio-something really gave me the business about being a troll and not having anything technical to add.

Actually, I said you bring zero value. The statement wasn't referring to just technical value. Perhaps you got confused with the other part of the paragraph where I said you lack the knowledge or credibility to refute anything Roger says. I was in fact referring to your lack of technical knowledge in that instance, but of course you already copped to that previously.
@ramtubes. 

You mentioned, that in the RM 9, two KT120 or KT150 output tubes could be substituted for four EL34s in each channel. Is there an advantage to using fewer higher output tubes as opposed to using double the number of lower output power tubes, or vice versa? In other words, is the former following a “simpler” path than the latter?