Krell KSA 50 PCB

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#9,523
You probably don't want your email on a public forum. You could possibly get all sorts of spam and/or scam emails.

You might want to ask the moderators to delete it. Or if you can edit it and remove it yourself.

In the future you can send it more privately by clicking on the user you want to communicate with and then click "start conversation".
 
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#9,526
I reoommend @grimberg's pcb method and use of TO247 transisitors.

I bought ready built modules using 3 pairs of TO3 transistors bolted to an aluminium bar. Even with a massive fan cooled heatsink, I had problems keeping the TO3 can temperatures below 75C.

You need to be able to bolt the output transisstors directly to the heatsink which will need to be fan cooled.
 
#9,527
Stupid question alert...

Can the diyAudio Universal Power Supply be used for the KrellClone? I'm baby-stepping my way through this build and struggling with a lack of information about the power supply. I'm planning to build it as a stereo amp housed in the 5U chassis from modushop. It's going to drive a pair of very high sensitivity speakers. Any pointers or recommendations?
 
#9,528
In each of my mono-blocks I used a Plitron transformer with two secondaries, one bridge rectifier attached to each secondary, followed by a 68000 μF capacitor. A total of 136000 μF per channel. You can see that in the pictures of my build linked above. That is similar to the original Krell which housed both channels in one case and used 40000 μF per rail, for a total of 80000 μF per channel.

krellinside02.jpg
krellinside03.jpg
krellinside04.jpg
 
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#9,535
batteryman said:
I reoommend @grimberg's pcb method and use of TO247 transisitors.

I bought ready built modules using 3 pairs of TO3 transistors bolted to an aluminium bar. Even with a massive fan cooled heatsink, I had problems keeping the TO3 can temperatures below 75C.

You need to be able to bolt the output transisstors directly to the heatsink which will need to be fan cooled.
Click to expand...
Please may I know which readymade module did you buy, there are so many to choose from and all look similar, and quality varies. Do you have a pic or links?
 
#9,538
I can't say as I've not tried others. The buid quality was fine. There was no way to kow whether the semicoductors were all genuine but the measured results were good.

My issues was the need for the L bracket mounting for the TO3 cans, which is why I recommended a version that uses TO3p or TO247 that can be bolted direct to a heatsink.

Even with a massive fan cooled heatsink, I wasn't happy with the TO3s running at 75C when the heatsink was at 55C - ie too much extra thermal resistance for my liking.
 
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#9,540
KRELL- CONNECTIONS.jpg


I bought these boards in 2018 but haven't worked on them due to confusion about the connections. Since they were purchased from eBay, there is no support available.

I need help clarifying the following:

  1. Are the connections between the boards correct? Should one cable connect the + and - supplies to both the output and driver boards before going to the power supply?
  2. I read in this thread that my board has an error and that one leg of the 1N4148 diode should be connected to the ground plane. Can someone confirm if my correction shown above is accurate?
  3. Can 2SC2240 and 2SA970 be replaced with KSA992 and KSC1845?
  4. I couldn't find substitutes for 2SA968 and 2SC2238. Can anyone suggest alternatives? As a last resort, I might try AliExpress, but I’m unsure if the transistors there are genuine.
Many Thanks in advance for your help
 
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