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Old 26th January 2010, 02:13 PM   #1
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Default Replacing Cap Across Filter Cap

Hi all. I'm new to modding tube amps and have a quick question.

I'd like to replace the .22 mfd Kimber cap in my 15+ year old Cary SLA 70A signature amp that is connected across the terminals of only one of the filter caps. I assume this cap is to keep AC noise from reaching the filter cap. The other filter cap does not have a cap across it's terminals. It only has a resistor (bleeder?) across it's terminal. My question is can I add a second cap across this filter cap with the resistor in parallel to further reduce noise or would this cause a problem? Thanks in advance.
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Old 26th January 2010, 02:32 PM   #2
TheGimp is offline TheGimp  United States
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In General, placing an additional cap across a present cap is not a problem so long as (1) it does not cause excessive current draw from the rectifier(s) (Particularly tube rectifiers), and (2) the additional capacitor has the proper voltage rating.

A schematic and more specifics on the type of cap you are going to use and what it's expected advantage is would be helpful if further discussion.
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Old 26th January 2010, 10:04 PM   #3
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Originally Posted by TheGimp View Post
In General, placing an additional cap across a present cap is not a problem so long as (1) it does not cause excessive current draw from the rectifier(s) (Particularly tube rectifiers), and (2) the additional capacitor has the proper voltage rating.

A schematic and more specifics on the type of cap you are going to use and what it's expected advantage is would be helpful if further discussion.
Thanks for the response. I do not have a schematic unfortunately and I certainly don't want to cause an issue in the amp by adding a second cap so I guess I'll just replace the single .22 mfd 600v Kimber that's in there. Any recs as to what I should replace it with? I'm thinking that a 600 v OD 716P might be good enough.
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Old 26th January 2010, 10:29 PM   #4
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Quote:
Originally Posted by Monjul View Post
I'd like to replace the .22 mfd Kimber cap in my 15+ year old Cary SLA 70A signature amp that is connected across the terminals of only one of the filter caps.
Why? What are you expecting to happen?

The Kimber cap, which is an MKP cap, should be fine. However, any electrolytics, such as the filter caps, are likely getting up there in age and may be ready for a refresh.
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Old 27th January 2010, 12:53 PM   #5
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Originally Posted by dsavitsk View Post
Why? What are you expecting to happen?

The Kimber cap, which is an MKP cap, should be fine. However, any electrolytics, such as the filter caps, are likely getting up there in age and may be ready for a refresh.
As thegimp said, as long as "it does not cause excessive current draw from the rectifier(s) (Particularly tube rectifiers)". If this is possible, I'd like to avoid it.
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