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Old 16th May 2005, 07:59 PM   #1
dorkus is offline dorkus  United States
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Default Dynaco SCA-35 fixer-upper

hi all,
being a solid state guy, i'm not up on my tube amp history... is a Dynaco SCA-35 any good as a fixer-upper platform for a modest tube amplifier? not looking for the ultimate in hifi performance obviously, just some tube thrills on the cheap. my friend has one he's giving away and i'm wondering it's worth the time to recondition/modify. he already spent a couple hundred on new tubes last year, so those may be worth salvaging.

thanks,
dorkus
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Old 16th May 2005, 08:02 PM   #2
SY is offline SY  United States
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Yes. Reasonably nice iron (outputs are 8K with UL taps, very hefty for the power rating), but you'll end up doing pretty much a wholesale replacement of the circuitry. The circuit is crude and the circuit boards are awful quality. Same with switches and plugs.

There's plenty of room to work in, though, and you can turn it into a very nice-looking unit.
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Old 16th May 2005, 08:07 PM   #3
dorkus is offline dorkus  United States
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hi SY,

long time no see. (i've been completely out of the DIY loop for a while now, got too busy with other things - so much for Son of Dork! ). thanks for the info... i'll Google around and see if i can find any good suggestions on improving the unit. i'll take a look at the original schematic as well.

cheers,
dorkus
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Old 16th May 2005, 08:40 PM   #4
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The SCA35 is a great donor, but as SY says the circuit and quality of boards & chassis is suspect.

I have an SCA35 project... iron is going on another chassis and i'll build up a circuit with a long-tailed pair on the front... mine will also borrow a PS Trafo from another unit to give me dual mono (the trafo on the SCA35 is reputed to be just a tad undersize)

dave
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Old 16th May 2005, 09:36 PM   #5
SY is offline SY  United States
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A ccs-loaded long tail is a good approach. If I were doing one, I'd consider a 12AT7- it's small, lowish distortion, cheap, and has enough gain that you can throw some feedback around the whole shmeer. In VA3, Morgan Jones shows a very nice little circuit (Bevois Valley), also a 1 tube input stage, that would fit just fine in the SCA-35 chassis.

Add a potentiometer and a switch and you've got a nice line-level integrated amp.
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Old 16th May 2005, 10:02 PM   #6
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Quote:
Originally posted by SY
A ccs-loaded long tail is a good approach. If I were doing one, I'd consider a 12AT7- it's small, lowish distortion, cheap, and has enough gain that you can throw some feedback around the whole shmeer.
I'll probably start with 6H23pi or 6AU6 strapped in triode... EF86 is i can come across enuff of them.

dave
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Old 16th May 2005, 11:22 PM   #7
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> some tube thrills on the cheap.

If the circuit boards are not toasted: just fix what's broke and enjoy it. The Dynas may not be the gold standard of high-end audio, but as a break from stolid-state sound they are just what you want.
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Old 19th May 2005, 01:07 AM   #8
jacky is offline jacky  Canada
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Default Re: Dynaco SCA-35 fixer-upper

Definitely.
Simply bypass the tone control circuit and short out the ceramic cap at the amp input (not needed unless your signal source has DC offset) will make the SCA-35 sound a whole lot better without spending a dime.
Replacing those light greenish blue color caps with polyproplene caps will further improve the sound.

Quote:
Originally posted by dorkus
hi all,
being a solid state guy, i'm not up on my tube amp history... is a Dynaco SCA-35 any good as a fixer-upper platform for a modest tube amplifier? not looking for the ultimate in hifi performance obviously, just some tube thrills on the cheap. my friend has one he's giving away and i'm wondering it's worth the time to recondition/modify. he already spent a couple hundred on new tubes last year, so those may be worth salvaging.

thanks,
dorkus
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