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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So Roger: new production tubes from our old Cold War rivals. Can the Russians really make and sell quality tubes at such low prices? A quartet of 12AX7's for $18 (shipping free!). We did that ourselves back 50-60 years ago. But that was when US tube production was in the millions for the radio/television market! Do Russian mfgr's have to compromise on material quality and less vacuum- pumping to sell at a low cost? 
I have bought a set of 4 Gold Lion (Russian) KT-66's for use in my pair of Heath W5's. $35 a tube! Originals sell for $200+ a tube (UK). They sure do look real nice! I still have the original US Tungsol 5881's in use. I wonder if the Russian ones can stand up long-term to the plate and screen voltages in the W5's?
I still prefer US, European or Japanese vintage production over the new stuff! 
Thanks for offering your tribal knowledge to the group.

I really like vacuum tube audio equipment.  Both Pre Amp and Amp.
It just sounds better.  (Ha....I have all C-J equipment.)

My design question for you is.....

I have always wondered if vacuum tube technology was abandoned prematurely (for solid state), and never fully exploited to its full potential?
Roger, you are being very generous with your time and your expertise. Thank you!

You have given me a container load of practical information which only comes from practical experience. Much appreciated! As requested, here are some details of my system.

My system is 98% analogue. Phono is integrated with the preamp. Twinned MATs reduce the noise floor. All caps in the signal path are air gap or vacuum, including RIAA. Battery power, filtered.

Speakers are 5 (soon to be 6) Quad 2905's. These have been modified for the Plitron step-up, which I will revisit - but that protection circuit is not at all transparent! It desperately wants attention, if not removal. The small disgusting ceramic caps in the phase ladder are being replaced with air gap (teflon is a big improvement on ceramic, but coloured). The larger disgusting ceramic caps are replaced with a chain of RTE styrene F&F caps. Air gap caps are made in the usual way.

Amplifier power comes from a big variac driving an isolation transformer, driving power transformers. Rectifiers are Ixys, feeding LCLCLC filters. Theoretically at least, this brings ripple down to the level of intrinsic noise.

Amp topology is reminiscent of the newer Brystons, but not close to identical. Transistors are AD, Toshiba, Sanken. All resistors are nude Vishay or DIY nichrome.

Theory as well as experiment have led me to suspect that much of what we hear is dielectric-sourced distortion. Accordingly, my caps are air-gap or vacuum wherever possible, styrene when not. Wiring is insulated and protected with unshrunk shrink-wrap, except at the ends to prevent corrosion. Just my poor observations in part repayment for your generosity.

Your expertise is highly valued, so anything you have to say is welcome. Thank you!