2. amps-preamps
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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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bdp24's avatar
bdp24
9,874 posts
 

Roger, here’s a question about light loading with the RM-200 Mk.2 amp: With a loudspeaker given a nominal 8 ohm load rating by it’s designer/manufacturer (it measures between 10 and 20 ohms from 20Hz to 20kHz save for the 60Hz-180Hz band, where it dips down to 7 ohms, centered at 80Hz), the RM-200 will of course put out at least it’s rated 100w/ch when connected to the amp’s 8 ohm taps. If it is instead connected to the 4 ohm taps (light loading), what will the amp’s output wattage be?

Because of the speaker’s relatively high and even impedance curve, it is not for the flattest frequency response I am interested, but rather the lowest distortion and longest tube life. I realize that with light loading those will be achieved at the cost of less power output from the amp. I have a modestly-sized room, and don’t listen at very high SPL, so am willing and able to accept that.

roberjerman
4,319 posts
 
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? 
roberjerman
4,319 posts
 
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?
roberjerman
4,319 posts
 
I still prefer US, European or Japanese vintage production over the new stuff! 
quincy
356 posts
 
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?
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