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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lemonhaze
417 posts
 
Hi Roger,
Am I glad I found this helpful thread.  I have a Mark Levinson 23.5 amp that hums.The hum is loud and stays constant in amplitude regardless of the position of the volume control. I am driving it with an Aikido linestage that I built and which from driving various power amps I know to be quiet. I tried lifting the earth leg first on the line amp and then on the power amp but hum stubbornly remains. 

I bought the amp used. I realise that it is quite ancient and probably needs to be re-capped. I took a look inside and it appears somewhat daunting.
 
prof
3,479 posts
 

Roger, thank you for the reply about cartridge impedance.
clio09
3,360 posts
 
I should have mentioned this, Roger built a very accurate switch box that has a long cable with a button switch on the end. I could sit at the listening position and click the button at various intervals (3 - 5 seconds generally) so going from A>B>A again was very simple. It was also easy to see which amp was in play.
clio09
3,360 posts
 
@ct0517 - thanks for the response. With the subs in place are you still running the Quads full range, the using the sub fior 60 Hz and under, or are the Quads completely cutoff at 60 Hz?
ieales's avatar
ieales
1,201 posts
 
We abandoned switchers as they were always audible. So rather than A-B, we had C-D or C-C. We were pretty meticulous in keeping paths as identical and as clean as possible having only the relay contacts as the additional connector.
One thing we never did, but probably should have, is have a simulated load for the off item to maintain thermal characteristics more closely.

I'd be curious if trained listeners can reliably detect the sound of the switcher.
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