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Krell KSA 50 pcb
Krell KSA 50 pcb
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Old 11th January 2019, 12:42 PM   #8981
Blitz is offline Blitz  Germany
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Quote:
Originally Posted by henryve View Post
I don't know of ANY KSA 50 that had MOSFET outputs.
Ok, maybe I misread that...which makes this project more intersting...is there a clear bipolar preference ? Seem to be different versions out there...
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Old 11th January 2019, 01:08 PM   #8982
Medisinmannen is offline Medisinmannen  Norway
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This is a 1:1 of original layout. It is this im using to build my clone.

It is also possible to use delta audio boards,but they are not the same as original(parts also differ). Well documented in thread.

I do not trust ebay for transistors/board with transistors.
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Old 11th January 2019, 01:19 PM   #8983
Dave murrey is online now Dave murrey  England
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Quote:
Originally Posted by Blitz View Post
Ok, maybe I misread that...which makes this project more intersting...is there a clear bipolar preference ? Seem to be different versions out there...
Hi I am also collecting parts to build a krell ksa 50.
What I have read from others early version was full class A
Mk11 version higher rail voltage is not full class A but sounds best.
you can also check this guide out.
bhttps://www.diyaudio.com/forums/diyaudio-com-wiki/152448-krell-ksa-50-clone-building-guide.htmlut sounds best.
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Old 11th January 2019, 01:31 PM   #8984
henryve is offline henryve  South Africa
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Quote:
Originally Posted by Blitz View Post
Ok, maybe I misread that...which makes this project more intersting...is there a clear bipolar preference ? Seem to be different versions out there...
These were some we used to build the clones:

https://www.onsemi.com/pub/Collateral/MJL21193-D.PDF

https://www.onsemi.com/pub/Collateral/MJL3281A-D.PDF

You can also get them in the TO-3P packaging as

https://www.onsemi.com/pub/Collateral/NJW3281-D.PDF

https://www.onsemi.com/pub/Collateral/NJW21193-D.PDF

Some of us could still source these in the older TO-3 packaging, but I doubt you will still get them now. Those on eBay is almost guaranteed to be fake. Rather use the modern packaged units from a guaranteed source like Mouser, Farnell and Digikey.
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Old 11th January 2019, 09:45 PM   #8985
Blitz is offline Blitz  Germany
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...ok and any recommendation on the board fitting to these more modern version ?
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Old 11th January 2019, 11:44 PM   #8986
THD+N is offline THD+N  United States
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Quote:
Originally Posted by Blitz View Post
Well, what is the recommended board version ?
Attached is the version most people built (including me).

The KSA50 is very dynamic and fast, but most of all "listenable". It has an extremely wide bandwidth (200kHz at 1 watt), low distortion and low noise.

Even though is is an "old design", I believe it is a benchmark even today. It is a very forgiving design and a lot of parts (many different transistors can be used) are not critical.

The design is tried and true as built by many DIYers.
Attached Images
File Type: jpg KSA50 Schematic.jpg (147.8 KB, 164 views)
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Old 12th January 2019, 12:18 AM   #8987
grimberg is offline grimberg  United States
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Starting on post #8883 I showed pictures of the 10th anniversary makeover of my KSA-50 mono blocks. I used PCBs designed by member Pinkmouse and created long output PCBs to better use the length of my heat sinks.
I have an unused set of the Pinkmouse PCBs and can also provide long output boards. If anybody is interested in building the Krell clone using those proven PCBs, contact me through private message.
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Old 12th January 2019, 11:44 AM   #8988
Blitz is offline Blitz  Germany
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Originally Posted by neychi View Post
Well, some people says that the latest version sounds best, some people prefers first mk2. I had no opportunity to listen every version of original ksa50 (just first mk2) but I can tell you that higher rail voltage do things better. I've finished two clones, one with Delta boards, and 37V DC rails (1.8 A bias, 3 pair of output devices, 300mV per device), and one with mosfet-ccs, 48 V DC rails (1,3 A bias, 2 pair of output devices, 325mV per device). The difference between this two amps is so obvious. The later has more punch, more authority but still has smooth silky highs which is exactly what I remember from listening original KSA50.

Dean
neychi, may I ask which boards did you use for your version with 48V and mosfet ccs ?

I can find some versions on aliexpress, but more for KSA100 if I get it right:

Click the image to open in full size.

from this offer:
KRELL KSA100 improved BA15MKII power amplifier kit Class A power amplifier board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group

Are these the Mosfet-Versions you talked about ?

medisinmannen, I got the schematics of your boards, they seem to be the early Mk2 version without mosfet ccs. They as well have some changes compares to the schematic from THD+N...(not sure how I can attach a pdf here)

Last edited by Blitz; 12th January 2019 at 11:50 AM.
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Old 12th January 2019, 12:39 PM   #8989
alibear is offline alibear  United Kingdom
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Quote:
Originally Posted by Blitz View Post
May I ask those who built it and compared it with other builds like Pass F5 or other class A SS power amps: Is it still worth it to build it or are other models superior...given that this was invented in the 80s...and yes, I wanted one of them as well when I was a student and could not afford them...so it is easy to convince me to build one, but really...should I ?
I built an F5 several years ago and I must say I didn't like it, this is just a personal opinion, and I am sure there are a great many who think differently.
I have a passively cooled KSA50 that is modified for 25 W output that I enjoy a lot. Also currently building another KSA50 that will be biased to at least 50W with fan cooled heatsinks.
Also worth considering is the Aksa Lender Alpha class A . I have built this and although not yet installed in a chassis is a very listenable amplifier that to my ears is very nice.
Best Regards
Alan
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Old 12th January 2019, 05:11 PM   #8990
neychi is offline neychi  Croatia
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Quote:
Originally Posted by Blitz View Post
neychi, may I ask which boards did you use for your version with 48V and mosfet ccs ?
Stolen Trademark Amplifier from Jim's Audio on EBAY
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