Krell KSA 50 PCB

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#8,065
neychi said:
@john65b

I have 36VDC rails loaded, 340mV per emitter resistor, 3 pairs output devices, cca 2 A total bias and 145 watts/channel.
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The 146 watts is your idle dissipation not class A output. Max class A is limitedby the bias current of 690mA per device or 2A per rail.

Whether it is 36v rails or 48v rails does not matter to class A output sans clipping. It does affect idle dissipation though.

With 36v rails you could get upwards of 140 watts Class AB into 4 ohms and about 250 watts class AB with tight supplies (4ohms) on 48v rails.
 
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#8,071
The end....

Sorry to report the last Krell Clone boards are on the way to their new homes. Thanks to Mark Gulbrandsen for financing the project, and letting me finish distributing the boards when he got too busy. I wish he was still participating here. So how many of you actually made it to a working amp? Mine is working but with clip leads and plywood 🙂 Hope to clean that up soon....

Pinkmouse may have the gerber files still if someone wants to run with Round 2, or they may be buried in the thread somewhere. Thank you for letting me help, and DIYAudio got $300+ in donations from Mark's kindness. 😀

Bob G.
 
#8,072
Mark did a great job ordering and getting the "second round" of Pink Mouse PCBs (I did the first) but he has been swamped at his real job. He is constantly on the road.

Bob, thank YOU for carrying on the torch and finding homes for the last of the batch!
 
#8,075
K-amps, you are using incorrect biasing on your KSA-50 clone. The actual Krell basing is 325mv +-5mv and that is the "sweet spot". You are running yours too rich and overheating the outputs for no good reason whatsoever.
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Does this not depend on your emitter resistor and # output devices?

I believe we are confusing mA and mV on Bias. 325mV means nothing if you don't know the emiter resistor and # output devices...I would think 325mA per device seems too low.....original was upwards of 650mA/device?
 
#8,077
john65b said:
Does this not depend on your emitter resistor and # output devices?

I believe we are confusing mA and mV on Bias. 325mV means nothing if you don't know the emiter resistor and # output devices...I would think 325mA per device seems too low.....original was upwards of 650mA/device?
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On a complimentary output stage I can get away with as little as 10mA per output pair and still get rid of crossover distortion on the scope.

I find with a quasi it needs a bit more current, nearer 100mA per output pair.
 
#8,080
325mV on .5 ohm emitter resistors is 650mA per device

KAmps said Max class A is limited by the bias current of 690mA per device...

Aren't you both saying same thing? How is he over driving his devices (40mA?)

I have mine at 610mV on .649 emitters, getting around 940mA per device...are you saying I am just wasting heat and there is no Sonic benefit??

Your attachment was not for KSA-50, but KSA-80/100/160/200. I remember the KSA-50 design was two devices driven to over 900mA per device.

Nelson Pass' position of raising bias as much as your sinks can take to better sound doesn't apply here (I know different design - single ended and he uses MOSFETS)??

Not trying to cause trouble...just interested in finding out. I wouldn't mind turning down the bias on my Krells...if there was a benefit...


Quick, hide that link before Dan makes them remove it!!!
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Got my copy...thanks.
 
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