Krell KSA 100mkII Clone

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#2,501
Testing my 3-chanel version of the amp on 4Ohm resistor I found that it rings on about 7MHz when going to AB.
I've tried to increase C6 and C5(Cdom) to 82pf, parallel R15(NFB resistor) with 20pf cap, but it didn't help. The only thing that helps is to increase bias till it in the pure class A. Please advise.
 

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#2,504
Luke, Xslavic,
Thanks for answers!
All of the 3 channels show the same behavior, but I've pulled one of my monoblocks and it behaves completely normal under the same conditions. They share pretty much the same topology, except the misbehaving one uses SC4793 + SA1837 in VAS - I'm going to replace them with MJE15034/5 and see what will happen.
I've checked DC around 1N5309 and it seems to be consistent with 3mA current source.

Viktor
 
#2,508
stolbovoy said:
Testing my 3-chanel version of the amp on 4Ohm resistor I found that it rings on about 7MHz when going to AB.
I've tried to increase C6 and C5(Cdom) to 82pf, parallel R15(NFB resistor) with 20pf cap, but it didn't help. The only thing that helps is to increase bias till it in the pure class A. Please advise.
Click to expand...
Length of the wires to the bases of the output stage was the problem. Reducing it to 2-2.5" did a trick
 
#2,516
It looks like this project is now dead with not many who received their PCBs actually building a working amp, unless you all did it in secret.

Let me know with a PM if you want to feel less guilty about it and sell me your PCBs. I will only need 2.

Pierre, if you are still around, maybe if nobody is willing to let go of theirs I might want to come and talk to you there in Bloubergstrand. I might even bring my surfski with for a quick paddle at Big Bay🙂
 
#2,518
KSA-50 PCBs

henryve said:
It looks like this project is now dead with not many who received their PCBs actually building a working amp, unless you all did it in secret.

Let me know with a PM if you want to feel less guilty about it and sell me your PCBs. I will only need 2.

Pierre, if you are still around, maybe if nobody is willing to let go of theirs I might want to come and talk to you there in Bloubergstrand. I might even bring my surfski with for a quick paddle at Big Bay🙂
Click to expand...

It is available here at Jim's Audio:
High Power Pure Class A Amplifier PCB KSA50 | eBay
 
#2,519
spurlte

I have the KSA50 already, mine is entering the last stages of completion and hopefully by the end of the summer holiday (here in southern hemi) it should be singing. I was refering to the KSA100.

Thanks to Loek for graciously offering up his PCBs for me, and they should hopefully be here soon.

Soon I might however have to grovel in front of Jacco for some 1N5309 CRDs, if he still has some left. Mouser has them, but only for a minimum order or 2500 units. Yikes!
 
#2,520
I found the 1n5303

please take a look at Newark

1N5309 - AMERICAN POWER DEVICES - CURRENT REGULATOR DIODE, 600mW | Newark/element14 Mexico

Let me know if I can help.
Best regards
Ramon Amandi









henryve said:
spurlte

I have the KSA50 already, mine is entering the last stages of completion and hopefully by the end of the summer holiday (here in southern hemi) it should be singing. I was refering to the KSA100.

Thanks to Loek for graciously offering up his PCBs for me, and they should hopefully be here soon.

Soon I might however have to grovel in front of Jacco for some 1N5309 CRDs, if he still has some left. Mouser has them, but only for a minimum order or 2500 units. Yikes!
Click to expand...
 
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