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.


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Youe are really great for doing this.  I have read that James Parker (Is that the right name) of Audio Research seems to design in a bit of added second harmonics to his designs. When I consider that some bands, most notably The Grateful Dead with their Wall of Sound array of MacIntosh amps, use tube amps for voices to add harmonics, this seems plausible.  Your thoughts?
Thanks for all you do as it is greatly appreciated! As a DIY tube enthusiast I would love to hear your suggestions on a good tube amp kit to build. Looking for at least 20 - 30 watts per channel. Can you point me to a place where such a kit is available for sale or at least a parts list and general instructions? A kit you would approve of in terms of sound quality and design. It would be great if you offered such at kit? Perhaps you do, but I missed it? 
Thank you Roger. Had many techs look at my issue. Isolation transformer had a 3 prong plug. It was a Torus unit. I ran the system single ended and balanced, floated the ground on all and only some units and used a structured process of elimination, had them all connected to one Shunyata power bar therefore only one outlet used, connected them to a complete different circuit in the house etc. Interestingly, the hum sounded different than a ground loop, it was loud as in you could hear it 30 feet away. Like the noise when you plug an RCA cable into a powered up subwoofer. A loud buzz. My new amplifier is a stereo unit. When I connected the monoblock amplifiers to the speakers and powered them up they were silent, when I plugged a balanced or RCA cable to either one the hum/buzz started even if the preamp was off! Never have a had this problem in 30 years of high end audio.... the only thing that made me post here was how the VP of this company spoke down to me when I explained my issue... never will I buy from them again. 
Wow! What a great thread! I’ve been reading through this all morning. The comments of others, and your answers, have brought up questions that I have, but had no reliable resource for answers! So, allow me to start with this: I own Magneplanars. I keep reading that tube amplifiers are a poor choice for these speakers. I like tubes though, and I have a tube preamp, and a hybrid power amp. The amp is a CJ EV2000, which uses 5751 tubes with a mosfet output to make 200 w/ch. I like the sound of my system, but it could be better. It seems to me that I don’t really need so much power, and I don’t need so much gain from a preamp. I rarely listen to music above 85 dB in my 21’x14’ living room. I’m considering buying a Schiit Saga passive/tube buffer “preamp” to replace my current preamp, and buying a quality tube amplifier. It is so difficult to compare things these days due to the fact that audio shops have all but disappeared. What are your thoughts about my situation in terms of “how much power” is appropriate, and “how will a quality tube amp drive my speakers”? Thank you for your insight!
Hi Roger, and thanks for offering to answer some questions for us.

In an earlier post, you offered to comment on specific brands, and I have a few in my stable.
-PS Audio
-McCormack (you already gave a nod to Steve)
-Symphonic Line (German)

As a follow-up on class D amps (and PS Audio), I recently got the PSA new Stellar S300 power amp, and would be interested in your input based on some of this information from their website.  The input stage is handled by their "Analog Cell", described as "a proprietary, fully differential, zero feedback, discrete, Class A MOSFET circuit."  The output stage is a "dual mono design.  [E]ach channel has its own, separate power supply. Each of the two channels is a complete and independent power supply and power amplification stage, based on a modern Class D ICE module, designed in Denmark."  Darren Myers is PSA's designer for this.

And here are the technical specs https://www.psaudio.com/products/stellar-s300-power-amplifier/#tab-specs

I like the sound of it, although interesting with no discernible harmonics.  I had never noticed harmonics in SS class A or A/B until I compared to this class D amp.

Thanks again for taking the time here!