Studio 20

20 Studio, 50+, 50PA, 50R, L100, B100, L120, L120PA, L120R, 120 SLAVE, B120, B150, L150, L200, B200, Concord, and SMF

Re: Studio 20

Postby javamagic on Sun Oct 26, 2014 5:04 pm

Papa Dog wrote:... are you saying that you do not think it is an Elpico build? on the Sound City Site there are pics of both and, to my untrained eye, they look to be the same, except for the badges. Have not compared the schematics, but I would bet that the differences will be slight if any.

It's definitely an Elpico built amp, rebadged for Sound City. I have the Elpico version and it has the same PCB marking, i.e. AC88. Mine (recently acquired) needs a bit of work - almost certainly new electrolytic caps. I changed the dropper resistors on the HT into the rectifier as they were smoking under load but other problems persist. The amp arrived with about 10mm of crud on top of the board which took a while to clean off, and a missing mains fuse. Luckily I had an old knackered transformer that used the same type and rating of fuse which was just as well as I've no clue where you can find replacements these days. I'd suggest rewiring the transformer connections to a standard modern fuse holder as the best solution. :)
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Re: Studio 20

Postby Racing on Sun Oct 26, 2014 10:03 pm

Been giving that some thought too as it seems about insanely impossible to muster fresh mains fuses.
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Re: Studio 20

Postby Papa Dog on Mon Oct 27, 2014 7:12 am

ya'll might check with the guys over in the Marshall subforum.
dunno the make of that transformer, but it looks like something I have seen in some older Marshalls
might be a source for them in Marshall resto suppliers
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Re: Studio 20

Postby bonds22 on Mon Apr 20, 2015 10:09 am

ind you a relay isn´t always a relay though. What you want are the high Q ones with selfcleaning contacts. What´s more they should never be involved in any of the tubes settings. Ie;the should always be decoupled completely. This to ensure noiseless operation.
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Re: Studio 20

Postby Racing on Fri Aug 14, 2015 6:30 pm

I hear ya.
The point here tho is that for completely "non intrusive" operation the way to do it,IMO,is to run an opto for let´s say the input grid of the PI. By using a regular opto for the incoming grid and simply making it hit really doesn´t matter what any and all relays do upfront.
The point here still is that altho optos certainly have a place...relays are relays. Ie; all said and done a relay mechanically makes sure there´s a complete "break" of a signal path.
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