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Old 30th March 2013, 07:35 PM   #11
generg is offline generg  Germany
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Originally Posted by Loudthud View Post
Why are there four heatsinks? Where are the chokes mounted? I don't see 'em.
they are in the PSU....
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Old 30th March 2013, 09:25 PM   #12
Zen Mod is offline Zen Mod  Serbia
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Originally Posted by Salas View Post
Is SJDP120R085 good for a drop in test to those arrangements? How close is that type to the custom PASS SIT-1 part?
- it is good , having an eye on bias

close - ( whatever type you meant - 2SK or SJDP ) - as heaven and hell
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Old 30th March 2013, 10:10 PM   #13
Salas is offline Salas  Greece
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The 2SK82 has less transconductance surely. When R085 looks like 4-5 Siemens, right? That would give better THD and Zo to those amps shown here. Still R085, PapaFET, and 2SK82, are all depletion mode with "ohmic" ID/VDS curves, correct? I was meaning to ask how close R085 to PapaFET may be. There are things to differ like Ciss, gm, ID/VDS intrinsic linearity. I would expect the custom PapaFET to be the best tweaked one for audio.
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Old 30th March 2013, 10:38 PM   #14
generg is offline generg  Germany
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In the Art Sit Nemesis article from Nelson is a small comparison between the R085 and the Papa SIT

"The R085, the best of the previous batch, was somewhat dry by comparison and the SIT was more lively and had better depth."

http://www.firstwatt.com/pdf/art_sit_nemesis.pdf
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Old 30th March 2013, 10:45 PM   #15
Salas is offline Salas  Greece
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Thanks for the link. Looks like a more evenly spaced curves part, also with less Ciss possibly under 100V VDS.
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Old 30th March 2013, 11:19 PM   #16
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I fiddled with them a year or so back. It's fair to say they have an extended triode region, but they're not as linear or triodey as a SIT in the region where you'd make an OTL amp. I'm sure they'd be fun to try nonetheless.

This isn't cleaned up, but you get the idea (range is 50V, 4A):
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File Type: png R085.png (32.3 KB, 374 views)
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Old 30th March 2013, 11:24 PM   #17
Salas is offline Salas  Greece
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Which one type exactly is on the curve tracer chart Michael? R085? Can't see the few amps region curves in so high amperage parts datasheets well anyway. They look very high gm at the many amps too but they should cut a lot of throttle when down low.
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Old 30th March 2013, 11:29 PM   #18
Salas is offline Salas  Greece
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P.S. XY mode? You got em one by one pasted off the scope! That's patience!
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Old 31st March 2013, 01:03 AM   #19
Mr. dB is offline Mr. dB  United States
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Originally Posted by audiong View Post
Hi Zen Mod,

Regrettably, after the kind words from The Master and you , my head no longer fits.
Time to start looking for a pair of 210 cabs !
I recognize the TD124, Rega arm, and DL103, and the A5, but what's that mounted on the back of the piezo tweeter?
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Old 31st March 2013, 01:17 AM   #20
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Which one type exactly is on the curve tracer chart Michael? R085?
Yes, that's the R085.

I have a little staircase generator in the works to speed the whole process up a bit.
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