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cbutterworth 11th December 2006 03:38 PM

which gauge wire for PSU????
I just bought some 16 AWG stranded copper wire for my Aikido PSU. It is really difficult to work with as it is pretty stiff and thick, especially compared with the mains input wires on my Hammond transformers and chokes, which are 20 AWG.

So, presumably then 20 AWG would be all that I need for 300 VDC at less than 100mA????


Joel 11th December 2006 03:57 PM

In a typical tube amp PSU, the voltage rating of the wire is the important thing, rather than the diameter. You can safely build a 100mA PSU with 22g wire.


zigzagflux 11th December 2006 05:37 PM

By the ampacity tables, you can use anything you want, even as small as 30 awg.

The real determining factor is actually mechanical strength more than anything. I find solid core wire much easier to deal with, just due to the fact that it holds its shape better, and can be easily trained and twisted.

However, with too much handling, solid core can easily break. So you reach a limit as to how small you want to go.

I currently use 22awg silver coated teflon hookup wire (solid silver is a waste of $$) for just about everything. It's low capacitance, easily worked, yet strong enough to be reliable. I even use it for point to point wiring on my perf board projects.

The silver coating helps minimize poor resistance due to oxidation (copper is very poor). Silver oxide is at least relatively conductive. If you need greater ampacity, its easy to twist and parallel conductors.

cbutterworth 11th December 2006 09:35 PM

Thanks guys for the replies.

I ended-up buying 20-AWG stranded wire from Home-Depot. It is certainly going to be easier than dealing with the thicker stuff.

Of course, now I actually have to do the wiring. The switch is already wired to the IEC and I used braided cable to Earth the chassis to the Earth-pin of the IEC. This means that I now have to figure out the Amperite tube delay relay and regular relay network. It is not complex, but going from paper to reality can be difficult.



Sherman 12th December 2006 12:11 AM

I found someone selling some teflon insulated wire rated at 600V on eBay for a good price. It is 20AWG (I think), stranded and tinned. Good stuff. I bought a several rolls in a few different colors (I like to color-code my wiring, makes it easier to follow later on). I can't remember the seller's ID though.

The teflon is nice since it doesn't shrink when soldering. There are a few situations when I would rather use solid core but overall I've been very happy with this stuff.

Richard Ellis 13th December 2006 04:38 AM

No stranded!!!
Do not use stranded wire thruout your build....Stranded wire is a sponge for RF.........I definately heard that once in class, I don't recall which class, perhaps RF theory, I don't recall what the theory was behind it, but I have my own theory.
If you could zoom in (1000X) or so on a cut stranded wire, what would the surface contact area be on two strands set side to side? Wouldn't there be a capacitance from strand to strand? The airspace inside?
Like I said, I don't know the theory behind it but that one factoid stuck in my head.....I suppose one could experiment with a scope to confirm or deny said theory.
___________________________________Rick........... .

Sherman 13th December 2006 12:52 PM

It would make sense that there would be some capacitance in stranded wire. A question is how much capacitance is there in pieces of wire a couple inches long and would it have an audible effect? Compare the effect of stranded wire to the effect of flux leakage from trafos, radiation from A/C mains, etc..

Sometimes theories, even correct ones don't always hold up in practice, there are so many variables to consider. I've used stranded wire throughout the last 3 amps I built with no problems at all. Looking at signals on a scope I'm satisfied.

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