can cap question

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JBP
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can cap question

Post by JBP »

Is their an advantage to using individual caps in the power supply verses a single can cap with the same values ? I'm considering a new build and the layout shows individual caps but a single JJ 40/20/20/20 500V would save room and simplify things. Thanks, Jeff
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rp
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Re: can cap question

Post by rp »

Not sure if there are technical/quality limitations but remember multi cans were used for decades through the golden age even in amps of the highest quality. There's the obvious disadvantage that if one fails you must replace the whole thing. Also you might have to run longer wire runs rather than place the caps close to each stage.

One thing to keep in mind is that 10 years from now you go to replace and CE will have stopped making them or be out of stock for 6 months and you'll be out of luck. Happened to me. Try and leave a little space inside and outside for future modding like a 20/20/20 or 20/20 outside and a 40 or 40&20 inside or 2X 20/20 outside etc.
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David Root
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Re: can cap question

Post by David Root »

One advantage to individual caps is you are not stuck grounding all caps to the same ground point.

Generally one is well advised to ground the power tube plate and screen caps at one point and the PI and preamp caps at a different point. You can of course do this with two can caps.

If the amp has global NFB, it is generally adviseable to connect the OT common lead to the PI cap ground point. In this case the PI cap should be grounded separately from both the power tube caps and the preamp caps.

Having said that my EH-150 Type 4 build used a single can cap for everything but it is cathode biased. It hums a bit because it has 6SQ7 octals that are being pushed fairly hard gainwise.
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rp
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Re: can cap question

Post by rp »

David Root wrote:If the amp has global NFB, it is generally adviseable to connect the OT common lead to the PI cap ground point. In this case the PI cap should be grounded separately from both the power tube caps and the preamp caps.
I wondered about locating the common for the OT w/ NFB. Must check my NFB amps I think I guessed it right. Love TAG.
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Structo
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Re: can cap question

Post by Structo »

I have read but I don't know if it is true that multi part cap cans are not as efficient at removing ripple from the power supply as discrete separate caps.
Whether that is due to the grounding or not I couldn't say.

I did use a JJ cap can in a 6V6 Rocket amp and it seems quiet enough.

I would say use separate caps if space allows but I wouldn't worry if I had to use one or two cans in an amp.
Tom

Don't let that smoke out!
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rp
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Re: can cap question

Post by rp »

Structo wrote:I have read but I don't know if it is true that multi part cap cans are not as efficient at removing ripple from the power supply as discrete separate caps.
I came across something like that too. You'd think some compromises might be made to fit four big caps into the space of one, but I've used and replaced several and never has issues or could hear any issues. You see multis on vintage Marantz, Macintioh, Fisher and that was the top of the tops. They must have concluded it's a fine compromise, if there is any. Considering David's points I'd avoid a 4X in a high gain amp but in classic guitar amps it's good enough, rawk on.
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