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
ramtubes's avatar
ramtubes OP
460 posts
 
@bdp24 


@jcder, everyone is going to recommend his own pre in answer to your question. Here are a couple to consider: There is a Hovland HP-100 listed on Audiogon right now (at an asking price of $2350), a fine line stage (I heard it in Brooks Berdan’s reference system for quite a while). The EAR-Yoshino 868L line stage, another good one, occasionally pops up for around $3,000. The 868 has one true balanced (via transformer) XLR input, if that matters to you. EAR Designer Tim de Paravicini very much strikes me as the UK’s equivalent of Roger Modjeski; old school EE’s with good ears and lots of knowledge and talent.


Happy Thanksgiving. May I remind everyone the purpose of this thread is to ask a technical question, not to discuss whose preamp is better.

This is the only time I will say this and I will ignore future preamp comparisons. 


ramtubes's avatar
ramtubes OP
460 posts
 
@ieales A balanced input is no guarantee of better sonics. The devil is in the details.Every audiophile should read Bill Whitlock’s AES paper"An Overview of Audio System Grounding and Interfacing" available here https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf


Thanks for the link.. Its 212 pages of slides. Power point :( I hope he takes breaks with refreshments. This could take hours. Id need 3 cocktails and a sandwich.

Can you direct us to a few pages with some meat on the bone. Im sure there is some wisdom there.
ramtubes's avatar
ramtubes OP
460 posts
 
@terry9  

Thanks for all your help, Roger. You really have opened up a stack of stuff for me to do. Much, much appreciated.

Hate to be pedantic, but I think that the 45uF figure should be 4.5uF, which is less of a problem: (75**2)  *  (800  *  10**-12)  = 4.5  *  10**-6. Your other concerns with the Vanderveen (got it right this time?) transformer remain an area of intense interest (and research!) to me. Thanks again!


You are indeed correct, it is 4.5 uF and still too much.  What raised my flag was that when i measured my speaker was at 80 pF for the 3.5 sq ft panel and I managed to make a transformer with about the same 80 pF capacitance and at 200 to 1 step up. Not much point in going further than that as half the power is in each. However had I used the plitron the numbers would be 90% of the energy absorbed by the transformer and 10% to the speaker. Thats a bad deal. 

Have you measured your drive capacitance? It is simply what you get stator to stator with a cap meter. I knew it when I was Direct Driving my 63's but that was 10 years ago. 

Not sure they still do but the 63's have a big 220 UFelectyrolytic cap in series with the hot speaker terminal to block DC. Do they still have this in some or all models? I could never understand why so large when 10 uf PPN would do.
mapman's avatar
mapman
22,389 posts
 
Back in the 70s selling most popular receiver lines from Pioneer to sansui to Tandberg the more powerful models in a line (generally up to 120 w/ch or so) ALWAYS sounded better at least at moderate or higher levels.


Clipping is always public enemy #1 to good sound. Avoid at all costs. Better to have overkill than clip on that great sounding full range dynamic recording.

Modern louder recordings are more prone to clip as well being louder overall so that ups the ante even more when it comes to how much clean power might be needed.

Also music not reproduced at lifelike volumes is not accurate reproduction rather a scaled down one. Nothing wrong with listening at lower levels but one is not even attempting to reproduce real music accurately that way.

Class D amps may be the most practical ticket to great sound along these lines for many these days that may have never really had one before. Good ones these days sound great, tend to be smaller and more managable, are often more cost effective per watt especially when more power is called for, and are most efficient which lowers power bills and TCO.
ramtubes's avatar
ramtubes OP
460 posts
 
@georgehifi



https://www.stereophile.com/content/leben-cs300-integrated-amplifier-measurements

JA does make mention of the ultrasonic resonance, but "maybe" because they’re an advertiser, didn’t make too big a deal of it.


Thanks for the link. When saw the picture again my mind went.. Ah, is this Luxman? Looks like Luxman. Does perform like Luxman. Must not be Luxman.

This amplifier is a strange combination of thoughts and performance. While the bass rolls off with out the boost, the boost is enormous when used and nothing in between.

Of course it didnt do the Quads well, "no bass grip". What did you expect when the output impedance is so high and I did not say damping. I want the word damping to go away as it is a most misleading term.

Look at horrible distortion curves at even low power. The only reason anyone could like this amp is on high sensitivity speakers like Art’s and at low levels. After a watt this amp is a mess.

I have been waiting someone who really wants to know ask me why damping is such an outdated term.



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