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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ON TONE CONTROLS

The typical bass control has a hinge point at 1,000 cycles, much too high. In my system I use the Subwoofer level control (100 Hz and below) to set the bass to the right level without making vocals muddy like most tone controls do. Typical bass controls have lift the male vocal 3 dB to get 6 dB in the low bass. We dont want to hear that. 

My woofer level control is right next to my volume control on my crossover and I note I move it several dB depending on the recording, listening level and bass quality.

For treble, usually I want a cut for bright recordings, rarely would I want a boost. A cut control is much easier to make than a boost. Typical cut/boost controls have a hinge at 1,000 also which is too low.

Whoever chose 1 KHZ as the hinge point made a big mistake, and once  made was copied over and over. I would choose around 200 Hz for the bass and 4 Khz for the treble and leave 200-4,000 unmodified.
Concerning tone controls, thank you,,, very good to know


It appears in design the good ideas are only done briefly by the few yet the bad ideas are done by the many and go on forever.

I think the choice of a single hinge point was the biggest mistake. Its actually easier to split them in two which I did in the C-4 preamp.
Roger, could it be the old 1kHz frequency was chosen in relation to the RIAA equalization curves?
@bdp24   Roger, could it be the old 1kHz frequency was chosen in relation to the RIAA equalization curves?


That would have been a better choice resulting in 500 Hz for the low hinge and 2 Khz for the high. I would prefer a larger gap as stated earlier. The single point of 1 KHZ is trying to hit the middle numbers wise but not sound wise.

The RIAA points were chosen by the density of program material. BTW the RIAA curve we are familiar with that is 40 dB of EQ from top to bottom is not the RIAA curve. It is the RIAA plus MM/MC curve.

The RIAA playback curve for a semiconductor cartridge is only 12 dB from 500-2,000 Hz. Thus RIAA boosts the highs 12 db and cuts them 12 dB on playback... Does anyone find this interesting or alarming that we call the RIAA curve the big one and not make much mention that it is for velocity transducers only?