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.


128x128ramtubes
peter_s
1,320 posts
 
Thank you Roger. You are a true asset to the audiophile community. Very generous.  
terry9
2,251 posts
 
Thank you for your kind offer, Roger.

I build solid state amplifiers, and like to match output transistors. At first I matched for HFE, then VBE at constant current similar to operating spec. Only later did I realize how much this parameter drifts over the first hour of warmup.

However, my latest amps are Class A, and I suspect that a more realistic match is obtained by culling outliers by HFE, then match from VBE using the bias at constant potential and sufficient to generate the operating current. Finally, instead of using matched emitter resistors, I use emitter resistors tailored to the output devices, so that each emitter resistor sees the same potential drop.

Your thoughts? Any advice appreciated.
bdp24's avatar
bdp24
9,510 posts
 
I wonder, how many have actually heard a Music Reference amp? Not a "trendy" brand, conservatively and timelessly styled (I happen to find the RM-200 minimalistily elegant, in a Scandinavian sort of way), few dealers, fewer reviews. I have found MR owners to be independent-minded, and secure in their own opinions, needing no validation from others. My kinda people.
ramtubes's avatar
ramtubes OP
460 posts
 
@uberwaltz 

 Now a novice question.

i have zero tube amp experience.

a lot of my equipment runs xlr connections

i have not seen many tube integrated amps sporting xlr inputs.

is there a good reason for this?

Balanced inputs take a lot of extra stuff. Most integrateds are going to turn the balanced into unbalanced right off because of volume control issues. The extra stuff in SS amps is a 50 cent op amp. In tube amps it would another tube or transformer. Much more expensive.

Balanced makes more sense on power amps where it is actually easy to do because of the absence of a volume control. 

Keep in mind just because a unit has a XLR input that is no assurance that the input is balanced.


bdp24's avatar
bdp24
9,510 posts
 
Roger, I assume the balanced/XLR-only input on your RM-200 is accomplished with a transformer. Do you wire it in accordance with AES File 48 (pin 1: ground, pin 2: non-inverted signal, pin 3: inverted signal)? Thanks---Eric. 
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