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-   -   threshold sa 50? (http://www.diyaudio.com/forums/pass-labs/136361-threshold-sa-50-a.html)

amp_guy 12th January 2009 12:27 AM

threshold sa 50?
 
It seems there are those who seem to think that the Threshold sa 50 was a better sounding amp than the similar wattage Krell.
Just wondering if anyone has seen the schematic and compared the differences. I have a almost completed KSA 50 clone, but just curious what the differences are being that I generally have a preferrence for Nelson's designs

jacco vermeulen 12th January 2009 09:44 AM

What is a SA-50 ?

The Threshold model from the same period that's wattage comparable is the SA/3.
Different ball game though, the SA/3 has an output stage three times the size of the KSA50 and had an identical price tag to the S/300, which was roughly twice the cost of the small Krell.
The SA/3 was succeeded by the SA/3.9e, looks close to identical from the top but has a different front end board.
The SA/3.9e has a cascoded dual JFET input stage, the Vas is also cascoded, plus the optocoupler biased Stasis output stage.
Soundstage (pugh) and tonal balance (more pugh) of the Class A Stasis amps is way beyond the capabilities of the KSA50.
All the parts needed to assemble an SA/ model are still fairly easy to locate, merely the original pre-drivers will be costly.

amp_guy 12th January 2009 06:23 PM

Quote:

Originally posted by jacco vermeulen
What is a SA-50 ?

The Threshold model from the same period that's wattage comparable is the SA/3.
Different ball game though, the SA/3 has an output stage three times the size of the KSA50 and had an identical price tag to the S/300, which was roughly twice the cost of the small Krell.
The SA/3 was succeeded by the SA/3.9e, looks close to identical from the top but has a different front end board.
The SA/3.9e has a cascoded dual JFET input stage, the Vas is also cascoded, plus the optocoupler biased Stasis output stage.
Soundstage (pugh) and tonal balance (more pugh) of the Class A Stasis amps is way beyond the capabilities of the KSA50.
All the parts needed to assemble an SA/ model are still fairly easy to locate, merely the original pre-drivers will be costly.

Oh yeah SA/3 right S50 is Plinius . You know your Threshold.
Are there any schematics floating around of the SA/3 ? sounds like it is much more extensive than the Krell.
The ksa that I have partially built is actually somewhere betwween the 50 and the 100 (output stage of the 100, power supply somewhere in between)

Thanks for the history lesson.

Nelson Pass 12th January 2009 06:59 PM

www.passdiy.com/np/threshold/thr_fe_89.tif

www.passdiy.com/np/threshold/thr_fe_90.tif

www.passdiy.com/np/threshold/thr_os_89.tif

:cool:

amp_guy 12th January 2009 07:09 PM

WOW just ask and POOF it magically appears!
many thanks.:D

jacco vermeulen 12th January 2009 07:33 PM

At the risc of Papa slapping me with a phonebook again : an important difference between the older 3-series and the 3.9e (and up) is the dual JFET differential input stage instead of matched BJT's.
The P got hooked on (J)FET's 20 years ago and hasn't detoxed since, in a manner of speaking.
/History channel Off

(warning, ask for a piccy of Jack first before you start with jammies funny stuff)

amp_guy 12th January 2009 09:01 PM

What can I say my first Design was a differential jfet lineamp, it was so sweet. I guess you never forget your first time.
We say we are cloning something here but more often than not the original is far removed from what ends up in the system making BTU's (and sometimes music)

tiefbassuebertr 18th October 2009 08:20 PM

Hallo Mr. Pass,
please let me know the presently URLs - thank you

Zen Mod 18th October 2009 09:32 PM

Quote:

Originally Posted by tiefbassuebertr (Post 1953481)
Hallo Mr. Pass,
please let me know the presently URLs - thank you

give me a buzz to >choky@neobee.net< and I'll send them to you


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