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-   -   18VAC transformer, what to do with it? (http://www.diyaudio.com/forums/power-supplies/155873-18vac-transformer-what-do.html)

asbus 29th November 2009 04:10 PM

18VAC transformer, what to do with it?
 
Hi,
I found a transformer lying around on my attic, so I thought I could build an amp with it.
I see there's only one AC secondary output, could I get +/- rails with that?
If so, I could use some tips on nice solid state amps running with +/-25VDC.

I understand I won't get much power out of 25VDC, but it would be fun to do something creative with it instead of throwing it away!

http://i46.tinypic.com/fd4sp3.jpg

Cheers

leadbelly 29th November 2009 04:56 PM

That trans is only 45VA, which is VERY small for a power amp. Also, with full wave rectification and no centre tap, all you'll get is +25VDC, forget about -25.

You CAN build a power amp with it, say something like a single-supply gainclone, but I would recommend you think along the lines of preamp or headphone amp.

paulb 30th November 2009 03:27 AM

Use double half-wave rectifiers to get +/- 25V. It will power an LM1875 amp very nicely. Look at the datasheet to see what power you can get. You'll need a heatsink.

Geek 30th November 2009 06:02 AM

Seems like a good transformer for making a tube amp with 18V (PLxx for european) heaters to me :)

Cheers!

Pano 1st December 2009 03:17 PM

That Gregg - he has toobz on the brain! :D

Since I have T-Amp on the brain - how about an AMP9 from www.41Hz.com ? Easy to build, sounds nice. Just right for your 18V tranfo.

gain wire 1st December 2009 03:43 PM

How about a variable power supply, either discrete (Pass transistor and op-amp feedback) or LM317?

Geek 2nd December 2009 02:38 AM

Quote:

Originally Posted by panomaniac (Post 1998262)
That Gregg - he has toobz on the brain! :D

Hehehehe, as usual! :D


Quote:

Since I have T-Amp on the brain - how about an AMP9 from www.41Hz.com ? Easy to build, sounds nice. Just right for your 18V tranfo.
Or a "FIWA"... five watt version of the SEWA :)

Cheers!


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