What to do with 700VA 10-0-10 transformer?

[kavermei]

Originally Posted by Jonathan Bright

I'm not an expert at this but I think you can wire the secondaries to get 20+20* by configuring them as voltage doublers. Look it up on the Net but you'll find its only the way the diodes are connected. Now you'll find that the frequency of the secondary voltage goes from 100/120 c/s to 50/60 c/s. But that is not a huge problem. With 20+20 you can make some serious Class A power amps. 8 or 4 ohms.

You're right, but doublers tend to have poor regulation and a lot of ripple. A regulator would be needed to get a decent result.

Someone suggested using two and chaining up the secondaries; this would be a better option were it not for the hugeness of the result (remember, these are 700VA units ).

A slightly more adventurous option would be to rewind the secondaries. On a toroid, this actually sounds harder than it is

[AndrewT]

35A through each secondary demands a lot of copper cross sectional area.
Find out if the secondaries are wound bi-fillar or tri-fillar or quad-fillar.
Separate the joints and identify the separate windings. Connect them in series to give a more useful voltage and current combination.

I had a 500VA 25V toroid. I opened it up to find tri-fillar. Adding one more winding gave me a 25+25+25+25Vac 500VA transformer.

[Lingwendil]

Originally Posted by Jonathan Bright

I'm not an expert at this but I think you can wire the secondaries to get 20+20* by configuring them as voltage doublers. Look it up on the Net but you'll find its only the way the diodes are connected. Now you'll find that the frequency of the secondary voltage goes from 100/120 c/s to 50/60 c/s. But that is not a huge problem. With 20+20 you can make some serious Class A power amps. 8 or 4 ohms.

Edit: *or you might actually get a bit more voltage. (Sorry can't remember the exact formula.)

As of this moment I'm building a class A Szekeres mosfet buffer with one of them, voltage doubled to give me around 32~36v after regulation, 1.08A per channel with an LM317T CCS. I've built high power buffers like this before, but these will be the first to use a common power transformer, and also the first to go over 18V supply. I figure that If I have these guys I might as well use one or two, and maybe sell the rest when I can.

[dave_gerecke]

I would have to give a second to the idea of using these in an aleph, or a First Watt or Zen series amp. That's right it the correct voltage region, and quite a healthy VA rating.

Peace,

Dave

P.S. If you do sell some of them, I might be interested!

[Lingwendil]

Originally Posted by dave_gerecke

I would have to give a second to the idea of using these in an aleph, or a First Watt or Zen series amp. That's right it the correct voltage region, and quite a healthy VA rating.

Peace,

Dave

P.S. If you do sell some of them, I might be interested!

maybe, btw, what state are you in, I'm contemplating selling a couple, just getting a feel for shipping. What would be a reasonable price for these trannies?