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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Power Supplies for Pre-amps,Crossovers, etc. posted by ccd on July 13, 2000 at 17:36:08:
Don't waste your time buying an expensive toroidal transformer
for your low-level stages. Toroids are not necessarily low-noise
devices--sure they cancel fields from a large distance, but close
in they can still be a problem.However, putting the transformer and input bridge in a separate
enclosure will help, especially if the enclosure is made of
steel. Fast recovery diodes with associated ceramic capacitors
to ground on both the input and output of the bridge is also a
good idea.After the bridge you can employ a linear regulator (not necessarily
an IC--a very good one can be made of a few discrete transistors)
on both the positive and negative rails. Make sure you put enough
capacitance on the output so that it is stable (read datasheet if
you are using an IC). Linear regulators also have a minimum
load to guarantee stated regulation, 5 mA is a common minimum
load.Minimize and/or filter the preamp's connection to the supply
rails -- to make full use of the inherent power supply rejection
of your op-amps. Many times noise can creep in through a subtle
path, like through the parasitic capacitances of a transistor.Replace the DC blocking capacitors in the signal path with
at least metallized polypropylene caps -- mylars aren't really
good. Polystyrene or paper-in-oil are supposed to be better than
polypropylenes but may be expensive and hard to find.Have fun.
Matt
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Follow Ups
- Re: Power Supplies for Pre-amps,Crossovers, etc. - mneedes 19:13:44 07/19/00 (0)
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