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Old 22nd January 2007, 10:32 AM   #1
Sony is offline Sony  Europe
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Location: Europe
Default Increasing preamp caps

Hi!

I need to refresh the four main caps on my preamplifier.
They are 1000uF 50V.

I was wondering if there could be some advantage (and no risk) in replacing them with larger ones (like 1500uF), which could provide more ripple current, and/or higher voltage (like 65V), which could make them last longer?

Thanks and regards!
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Old 22nd January 2007, 04:54 PM   #2
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Join Date: Jan 2007
Default Re: Increasing preamp caps

Quote:
Originally posted by Sony
Hi!

I need to refresh the four main caps on my preamplifier.
They are 1000uF 50V.

I was wondering if there could be some advantage (and no risk) in replacing them with larger ones (like 1500uF), which could provide more ripple current, and/or higher voltage (like 65V), which could make them last longer?

Thanks and regards!
I don't see how replacing the caps with higher voltage ones could be a bad idea (other than that they are physically larger).

Replacing them with larger ones might help; it helped the preamp in my system a lot. Safetywise, you have to be sure that the transformer and the fuse can carry the peak currents (especially during start-up). I don't advocate this, but I myself just replaced the fuses and my transformer still works fine.

While you're at it, you might also take a look at replacing the diodes by possibly better models, and denoising them with some small parallel capacitors.

The more specs you give on the thing (transformer rating, component numbers, etc.), the more suggestions we can make.
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Old 22nd January 2007, 07:59 PM   #3
AMV8 is offline AMV8  United Kingdom
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Hi Sony

I do not have any details of your pre amp/equipment so these are only general comments.

If you are thinking of increasing the voltage of the caps then first check the voltage across them. The capacitor voltage needs to exceed that voltage. For example if the voltage across the capacitors reads 25v then I would install 36volt capacitors.

If you want the capacitors to last longer ( and sound better ) then I would install 105 degree capacitors and not 85 degree capacitors.

Increasing the capacitance may or may not help. In some case it does - older equipment sometimes has under designed power supplies. For example I have just upgraded an old tuner from the 1970's. That had 450uf per rail of capacitance. However the sound had little base and that base was badly defined on complex pasages. I gradually increased the capacitance per rail until the base increased and became firm. You should not need more than about 2000uf per rail. Also best not to add more unless the power supply has been designed to accept greater values.

I also add polystyrene bypass capacitors across the power supply capacitors.

Hope this helps.

Don
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Old 23rd January 2007, 09:25 AM   #4
Sony is offline Sony  Europe
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Join Date: Sep 2004
Location: Europe
Thanks for the great tips!

I have just got this preamplifier - a 15' years old DENON DAP-2500A that includes a digital block.
Given its age, I expect the electrolytic caps to be somehow dry.

The bass is exactly where I feel there's a lot of space to improve.

As soon as I know more details I will return with the data. Meanwhile I will try to obtain the schematic.
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