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Old 18th March 2010, 04:32 PM   #11
jcx is offline jcx  United States
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poeple have wrapped a op amp gain stage around a chip amp - compensation is fun!

My ZD-50 ultralow distortion chipamp.

other ideas include push-pull Class A biasing of 2 parallel chip amps

or just a limited output bias "Displacer"


I belive Linn sold a 3 chip/channel paralled tda729x amp for > $3K
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Old 18th March 2010, 05:53 PM   #12
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Quote:
Originally Posted by ratza View Post
I really REALLY doubt that you have that gain. Perhaps it was 22.5 and 12.5?
You can doubt it all you want be that is the fact. This is part of the reason it works so well. Composite amplifier.

Last edited by sumaudioguy; 18th March 2010 at 05:54 PM. Reason: more info
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Old 18th March 2010, 06:01 PM   #13
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Didn't Linn use the LM3886 in some products too?
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Old 18th March 2010, 06:10 PM   #14
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Default my 3886 chip amp

Quote:
Originally Posted by AndrewT View Post
I think he meant open loop gain.
But at 10kHz that would imply about 100dB of feedback.
How does he make it stable with that much feedback?
AV=+20 or 26dB gain with feedback. Yes 100dB of feedback at 10kHz. "If your going to use feedback more is better so most is best." quote of John Gordon Iverson. In that vain this amp has a ton of feedback and gain. Works far better than it has any right to and is stable into any kind of load. I could barely get it to ring part of one cycle driving .1F or .5F load with 20kHz square wave and no resistance. Full power bandwidth is 110kHz.
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Old 18th March 2010, 06:42 PM   #15
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by analog_sa View Post
Stunning claim. Never even listened to a boombox?
Well that's not serious audio is it lol

OK I'll come clean... over the years I have repaired countless "grot boxes" and "Grumpstrads" etc with there TDA2030's and STK"yet another version" etc etc.

But I have never built a chip amp or listened to a good commercial one.
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Old 18th March 2010, 06:45 PM   #16
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Quote:
Originally Posted by sumaudioguy View Post
My proprietary high gain 3886 chip amp competes (according to many others who have listened) well at the $3000 level for a stereo amp.
I suspect a lot has to do with the implementation... and using and employing the device "sympathetically" as I like to call it.
Which it sounds like you have done
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Old 18th March 2010, 06:58 PM   #17
Mooly is online now Mooly  United Kingdom
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jcx

The ZD-50 looks quite impressive from a quick look through the articles and having a slook at the scope traces.

I'm a great believer in real world measurements.
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Old 18th March 2010, 07:02 PM   #18
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You're posting in the chip amp lovers forum, what kind of answer do you think you're going to get?
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Old 18th March 2010, 07:11 PM   #19
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Quote:
Originally Posted by richie00boy View Post
You're posting in the chip amp lovers forum, what kind of answer do you think you're going to get?
I suppose I could always ask in the, hmmmm, cough, Pass Labs forum
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Old 18th March 2010, 07:40 PM   #20
tomchr is offline tomchr  United States
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Quote:
Originally Posted by sumaudioguy View Post
Has 225dB gain at DC and 125dB gain at 10kHz. Vanishingly small distortion.
Composite amp. Oldest trick in the book. I looked into doing something similar. It can certainly be done, but compensation becomes a major challenge as the amp will not be stable at a closed loop gain of 20 V/V with simple resistive feedback. It's nice to see that someone had the same idea and made it work. Nice work! Could you show some measurement results?

~Tom
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