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
pryso
1,928 posts
 
tomic, I have a B&K 707 tester I got many years ago at an electronics swap meet. I really don’t know all that much about electronics but the B&K is easy to use and I’ve found it very helpful in identifying bad tubes -- not just strength but shorts and gas as well.

I would suggest finding a manual for your 667 if you can. Given the age the calibration described there may be beneficial.

Also I've seen positive reports on the Tubes4HiFi kits, including amps.  I have an SP-12 line stage custom built by Don Sachs which is wonderful.  But the basic unit has favorable reports as well.
chubaka
28 posts
 
What are rails and what to they do
tomic601's avatar
tomic601
12,911 posts
 
 @pryso  thanks ! fortunately the 667 is coming checked out and calibrated by reputable tech and includes the manual and tube charts. I do have a decent Fluke DMM also, so really looking forward to this...I built a bunch of Hafler kits back in the day, but never a tube unit...

fun

RM probably rhetorical but how do we get back to those fun days...

??????
devilscucumber's avatar
devilscucumber
13 posts
 
Hi Roger,I have some old Martin Logan Sequel II's which when repanelled no longer sounded pleasant with my Plinius Integrated 9100 (100w), they became overly bright and shouty. I ended up bi-amping with a Perreaux 6000B (300w mos-fet) running the panels, while the Plinius now drives the subs, my question is can you recommend a cost effective tube amp to drive these speakers, (which dip down to 2 ohms?) I live in NZ (240V/50Hz). I must admit most of the discussion on this thread is well over my head, but your experience in these matters is invaluable to help novices such as myself
georgehifi's avatar
georgehifi
10,312 posts
 
I have some old Martin Logan Sequel II’s which when repanelled no longer sounded pleasant with my Plinius Integrated 9100 (100w), they became overly bright and shouty.



All ML esl's need amps that can handle the load "below" without becoming tone controls and stay stable doing it.

Stereophile tests:
"The speaker drops to 3 ohms at 440Hz and to a hair over 2 at 24kHz, from which I infer that puny amplifiers, current-wise, should best be avoided. (Music has considerable energy at 440Hz, though only the occasional high-level cymbal crash will cause copious globs of HF current to be drawn from the amplifier.) MartinLogan claims a phase angle of 45° or less across the range; this graph confirms that to be the case, but the speaker’s ability to shut down the Krell with prolonged pink-noise drive did worry me."
https://www.stereophile.com/images/archivesart/99Seqfig01.jpg

Cheers George
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