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Topic: Session 400 - Sarno cap upgrade?? |
Todd Brown
From:
W. Columbia , South Carolina
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Posted 21 Dec 2011 4:43 pm |
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I'm just gonna put up a bunch of pics of my Session. I'm hoping I can get some help on what all has been done to it from you guys that know.
I think some of the caps are aftermaket, the bright blues ones, and( I don't know what they're called), 4 of the long white cap looking things look to be different. They have 10w stamped on the side, what are those??
I'm pretty sure the huge aluminum canister looking filter caps could probably be upgraded! Does this look like a good candidate for what Sarno recommends for cap upgrades?? Thanks for your help...
Last edited by Todd Brown on 21 Dec 2011 11:42 pm; edited 1 time in total |
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Bill Terry
From:
Bastrop, TX
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Posted 21 Dec 2011 7:32 pm
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I'd say a lot of the caps look original, maybe not the big filter caps. You can still see the 'goop' that Peavey put on a bunch of the components at the factory to keep them from vibrating or moving around. You have to break that stuff off to change a lot of the electrolytics.
The big '10W' square things are resistors. Some look like they may have been replaced at some point, but you never know. I'm sure Peavey bought components from various vendors and they may not have all looked the same.
Maybe Ken Fox or Brad Sarno will chime in. Brad has a mod where a lot of the coupling caps are replaced with audio grade replacements, but I haven't heard an amp with that mod done. I can't seem to find that link to his Session 400 page, maybe it's still up and somebody will post it. Definitely worth checking out.
I agree with what somebody said in another recent thread about these amps, they sound pretty good without any mods. That said, you've got some pretty old electrolytics that most would probably replace as routine maintenance, including the power supply filter caps if you don't know how old they are.
_________________
Lost Pines Studio
"I'm nuts about bolts" |
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Todd Brown
From:
W. Columbia , South Carolina
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Posted 21 Dec 2011 10:19 pm
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http://home.earthlink.net/~bradsarno/session_400page.html
Here's that link I think you're looking for Bill. I've been looking at this page. I guess I probably have a few questions for Brad. The 2 - 2.2uf yellow caps w/ black writing in the power section look as if they've been added to the board, not just replacing existing capacitors. They just don't match up with mine. They have to be ones that Brad has added for some reason. Mine is a 76-77 plastic front. It shouldn't be any different from his!
Also, what are some sources for these good audio caps? If Brad would let us know where he sourced all the caps he used in his upgrade, that would be great, or any one else who's done this upgrade based on his page.
Whats the opinions on whether I should do it myself, or have a local tech handle it. Save the headache. Or I could send it to Peavey and let them just update the filter caps and whatever else they think it needs and leave it alone. What do ya'll think?? |
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Michael Hartz
From:
Decorah, Iowa, USA
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Posted 22 Dec 2011 9:46 pm Caps source
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| I just ordered all the caps to do my '75. I ordered them from Mouser Electronics. They have great prices and fast shipping. |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 24 Dec 2011 8:04 am
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Todd, if you are experienced in working on circuit boards, replacing components, and have good soldering skills, you would not have a problem. Just order the correct components and have at it.
Otherwise, have a good tech do the work for you.
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Best regards,
Mike |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 24 Dec 2011 8:59 am
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It's been years, maybe 9 or so, since I created that webpage. So likely a bunch of part numbers have changed from the old list. But the basic idea behind the mod is to
#1; preserve the original circuit component values. No alterations to Peavey's amp in that regard.
#2: replace all of the electrolytic cap's in the power supply as they are well aged now and need to be refreshed
#3; replace the ceramic disc type cap's in the tone control circuit with mylar or polypropylene film types. They'll just sound better.
#4; replace the handful of small electrolytic cap's in the audio path with something better sounding. I recall the value being 2.2uF. You can use mylar or polypropylene film types, or you can try some nice, audio-grade electrolytics instead. For audio grade electrolytics I like Elna RFS (aka: Silmic II) or you can use the Nichicon Muse electrolytics. Both of these types of caps sound great for guitar audio, and since they're electrolytics, they're compact and affordable.
We're basically taking a great amp design and taking it to its real potential by giving it a very high quality, clean and silky signal path. And of course then we're doing required maintenance by replacing the power supply filter cap's.
Brad |
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