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Old 20th April 2007, 10:02 PM   #1
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Location: oakland
Default Best bias for 400a/S300?

hi all,

this will sound a little stupid, but I'm picking up a 400a that's been most likely factory updated to S-300 in the early 80's. the owner is not sure which model, but jon soderberg is almost positive it must a S-300. he said there was no upgrade program to STASIS-3.

so, question is, what is the best setting for the S-300. in case the amp is a stasis-3, will the setting work for either amp?

right now, the owner says he can leave his hand on the sinks all day. so, probably running on the cool side.

I'll crack it open when i get it and post some pics.

thanks,
Robby
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Old 20th April 2007, 10:56 PM   #2
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The best value is the one that runs the heat sinks at
50 to 55 Deg. C. after warmup. This is the temperature
at which you can put your hand on the sinks for about
5 seconds or so.

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Old 20th April 2007, 11:12 PM   #3
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Join Date: Apr 2005
Location: oakland
wow, that was fast Nelson. thanks!

one last thing. this was taken from jon's website. about the early stasis amps:

Many of these units had poor thermal tracking ability. Thus, many were biased too cool to fully take advantage of Class A operation. Vintage Amp can modify the bias circuit and replace the main capacitors for improved performance.

what do i do to fix this problem? i'll put in new main caps anyway.

Robby

Quote:
Originally posted by Nelson Pass
The best value is the one that runs the heat sinks at
50 to 55 Deg. C. after warmup. This is the temperature
at which you can put your hand on the sinks for about
5 seconds or so.

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