18VAC transformer, what to do with it? - diyAudio
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Old 29th November 2009, 05:10 PM   #1
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Default 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!

Click the image to open in full size.

Cheers

Last edited by asbus; 29th November 2009 at 05:34 PM.
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Old 29th November 2009, 05:56 PM   #2
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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.
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Old 30th November 2009, 04:27 AM   #3
paulb is offline paulb  Canada
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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.
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Old 30th November 2009, 07:02 AM   #4
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Seems like a good transformer for making a tube amp with 18V (PLxx for european) heaters to me

Cheers!
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Old 1st December 2009, 04:17 PM   #5
Pano is offline Pano  United States
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That Gregg - he has toobz on the brain!

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.
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Old 1st December 2009, 04:43 PM   #6
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How about a variable power supply, either discrete (Pass transistor and op-amp feedback) or LM317?
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Old 2nd December 2009, 03:38 AM   #7
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Quote:
Originally Posted by panomaniac View Post
That Gregg - he has toobz on the brain!
Hehehehe, as usual!


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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