Krell KSA 100mkII Clone

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spurlte

Banned
Joined 2011
KSA50/100

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!
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I should have mentioned that Jim's Audio KSA50 was available as KSA100 by adding a few different components and more output boards. Search diyaudio for KSA100 Jim's Audio. But you have yours now. Good luck, spurlte
 
V

vdavidov

Member
Joined 2005
Krell KSA 100 MKII station building, I hope to finish it in a few months.
It remained the only pair of transistors 2SC2238 and 2SA968 not find them. Transistor: MJE15032, MJE15033, MJ15003, MJ15004 ordered from Mouser, 2SC2240, 2SA970 ordered from hifituning24.de, 2SK2013, 2SJ313 ordered from Ebay user alweit of Israel.
Toshiba 2SC2238 and 2SA968 looking on Ebay are from China and Hong Kong do not expire no confidence and I think other users diy audio. I want to use the same transistors.
 
S

spurlte

Banned
Joined 2011
2SA968, 2SC2238

vdavidov said:
Krell KSA 100 MKII station building, I hope to finish it in a few months.
It remained the only pair of transistors 2SC2238 and 2SA968 not find them. Transistor: MJE15032, MJE15033, MJ15003, MJ15004 ordered from Mouser, 2SC2240, 2SA970 ordered from hifituning24.de, 2SK2013, 2SJ313 ordered from Ebay user alweit of Israel.
Toshiba 2SC2238 and 2SA968 looking on Ebay are from China and Hong Kong do not expire no confidence and I think other users diy audio. I want to use the same transistors.
Click to expand...
have you had luck in locating your transistors? How far are you with the KSA-100? Where are you going to get your output heatsink?
 
V

vdavidov

Member
Joined 2005
spurlte said:
have you had luck in locating your transistors? How far are you with the KSA-100? Where are you going to get your output heatsink?
Click to expand...

Single transistor which I found Toshiba 2SC2238 and 2SA968. On Ebay I do not inspire confidence in buying from China and Hong Kong.
I miss filtering capacitors are not decided on its purchase and I are missing a few pieces. Krell finish in 4 months.
Build two monoblocks in class AB and if you are satisfied with the sound, like in about 1 year 2 monoblocks class A building with passive cooling.
Toshiba 2SC2238, 2SA968 transistors original find, U.S. ?
 
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stolbovoy

Member
Joined 2004
I've built 9 channels for LCR tri-amped speakers using this thread. After 6 month of running fine, one of the channels started to die every half an hour or so. The reason is failing Q3 (negative rail LTP "input" transistor, the left bottom 2SA970 on the schematics). Here is what I see after failure:
1) Dead transistor measures with ohmmeter fine.
2) Amplifier output is close to the negative rail (-45V).
3) Q3/Q1 base are about - 5V
4) After replacing the transistor everything seems fine.

Here is what I've done except just replacing transistors about 7 times already:
1) Put DC blocking capacitor on the input
2) Put 2 by 3 diodes between Q1/Q3 and Q2/Q4 bases in opposite direction to protest the Q1, Q2, Q3, Q4 EB junctions from reverse voltage

I have separate power supplies for LTPs and VAS + output. The first one is stabilized 60V shared with the other 3 channels on the same chassis. The second one for this particular channel is 45V. The input is from a crossover on the same chassis.

What can cause it?
 
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S

stolbovoy

Member
Joined 2004
BenY said:
Feel free to take it to the extreme if you like walking on the edge.
twice the load on the driver stage plus cutting it`s ability by 50%.
it`s a sure recipe for overload and circuit failure. but hey, it`s your money...
Click to expand...
Why? What if he will keep the total bias the same? Even if the total bias current will be twice of original will it put the drivers outside of SOA?
 
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