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Old 15th April 2013, 04:41 PM   #1
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Default Recapping Quad 99 - simple question..

Hi there. I've completely re-capped my Quad 99 Pre-amp with new, low impedance low leakage devices. All is well.

However, on the board, I noticed some electrolytics rated 10uf at 50v which were green in colour and clearly have no "+" or "-" [on the cap or the pcb]

I'm making an assumption they are NP electrolytics ? They are physically the same size as the standard electrolytics on the board (I replaced all 10 of them plus plenty of others...)

All of the caps I changed were in the power supply, but these look like they are in the signal path.

Assumption 1:- If I change the cap value, something might happen to the sound
Assumption 2:- as they are in the signal path, that is not always a good thing
Assumption 3:- I can bypass... with a link.. but it's a risk

If I wanted to "upgrade" the quality of the cap, what type should I shoot for ? Tantalum ? Polypropelyne ?

Any thoughts ?

Rgds
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Last edited by clubsport911; 15th April 2013 at 04:45 PM. Reason: additional Q
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Old 15th April 2013, 05:39 PM   #2
Mooly is offline Mooly  United Kingdom
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If they had no polarity markings then its safe to assume they are bi-polar electros.

If you change the value of any cap in a signal path then the response is altered in some way depending on the time constants in the circuit. If you make the cap larger the low frequency response is extended. That can be a problem if the circuit has a "settling time" and larger values of C cause it to make thumps/noises on power on and off. That's just one reason.

I wouldn't bypass any with a link unless you have the circuit to look at to see what they actually do. And just because they are bi-polar doesn't mean they have no static DC conditions across them.

I would think anything other than an electro would be too large physically. A definite NO to tants
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