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imperfectcircle 9th June 2010 06:38 PM

1n4004 upgrade?
Im doing some upgrades/mods to an old Exposure integrated amp and the first thing im working on is the pre-amp section. Im going to start on the power supply which uses good quality parts but is very basic.

power trans> 4x1n4004> 2x 10,000uf/63vs> lt317/337> 10uf/50v= +/-18v

Just curious if schottky or hexfreds would be an upgrade to the 1n4004's? I also plan on upgrading the voltage regs.

bob91343 9th June 2010 06:41 PM

I don't see any advantage to changing.

imperfectcircle 9th June 2010 07:41 PM

Thanks, what about a small .01-.1uf cap across each diode? Ive seen this done before to reduce noise.

bob91343 9th June 2010 07:46 PM

Unless you have a problem, don't fix it. I have been working in the field for many years and have yet to add such capacitors.

Enzo 9th June 2010 09:21 PM

I'm with Bob here. If it works, stop fixing it.

If you want to upgrade something, I think a good place to start is to assess the areas the performance lacks, and then determine an approach to correct that. If you are getting noise, then we take steps to reduce it, but if noise is not an issue, then what's to reduce?

After some years, the electrolytic caps can start to get soft. The semiconductors just might last longer than you do. The whole point of the power supply is to provide smooth, clean DC power. So are both polarity main supplies sitting at about the same voltage? Ripple free? Under heavy load from the power amp, do they remain pretty clean? And those +/-18v rails, how do they look? are both rails at about the same voltage? Clean? In my humble opinion, it is more important the two 18v rails be the same, rather than whether it is 18v or 17v.

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