2. amps-preamps
  3. 140029-80294

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
clio09
3,354 posts
 
@ks2 - When Roger refurbishes an RM-5 the preamp gets computer tested pre-end of Soviet era SLN 6922 tubes. That is the preferred tube and the lowest noise 6922/6DJ8 tube he has tested.

FWIW - I have used them in my RM-5 Mk IV, RM-1 (12 tubes total), RM-4, and the as yet unnamed phono stage/tape head preamp. So I can attest to Roger's findings.
ieales's avatar
ieales
1,201 posts
 
The talk I saw about the DIY kit version of the First watt B4 was maybe six months ago, on a Nelson Pass-related DIY Forum site.
"However, there is progress. The DIY versions of the SL crossover and
a version of B4 should be in the store in a month or so, starting with just
the pcb + Jfets kit, to be followed by more complete w/ parts versions."

Nelson Pass in diyAudio Pass Labs 2018-02-13 : https://www.diyaudio.com/forums/pass-labs/165756-pass-labs-b4-crossover-questions-post5340382.html
clio09
3,354 posts
 
@ieales - Thanks for digging that up. From what I read in the link if the B4 kits were to be available in March or so, then they are either quite delayed or perhaps they were made available and sold out. I have the SL kit on a fully populated board but would much prefer a B4 kit.
prof
3,471 posts
 
Question:

What type of sonic issues occur as tubes get old? 


I had a tube in my CJ power amp fail, and the local shop said it was getting time to replace all the tubes.  But what is likely to happen if they are just left and keep on running?  Is it eventual failure?  Or does the sound start to alter in any way? Frequency response?  Dynamics, whatever?

I have the same question for my CJ preamp.  I know one aspect of tubes getting old: it now has a raised background "hiss" that it didn't have years ago when I bought it (so I've just bought replacement tubes).  But other than possible tube noise floor raising...is the actual sound likely to alter in any way as tubes age?

Thanks.
jetter
3,033 posts
 
I am very interested in the answer to prof's questions above. Especially as it pertains to what impact aging tubes will have on the sonics of a preamp, other than "hiss"?  I think another way of asking the question is that if you replace a set of aged preamp tubes (having no hiss) with an identical new set, will you hear a difference?
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