DC to AC isolated converter options?

[SISKO]

Hi there, im searching for ways to convert 9v dc to 9v ac @ 500ma to power my digitech xp100 from my regular power supply. Ive started desiginig a switched psu, but its gonna be a slow process as i dont have much free time to work on it.

So, in the meantime im looking for some other options i might not be consdering or at least a doable idea. Im not worried about EMI at this moment. First it needs to work, then ill look into details.
Im not quite sure if the xp100 can handle a square wave or if it needs a sine one. My guts tells me it can accept a square wave as it has some ferrites to filter it.

Heres is a schematic for the xp100. PSU section, page 3, bottom centered.
http://experimentalistsanonymous.com/diy/Schematics/Vibrato%20and%20Pitch%20Shift/Digitech%20XP100.pdf

My first raw idea was to build a 50Hz sine generator, amplified with transistors coupled to a transformer (one that i should wind it myself as its gonna be a low watt type and 1:1).
Another one was kind like the last one but with an LM386 feeding the transformer, but didnt get any further with this.

Any one tried this before?

[defaced]

What does the xp100 do to the AC inside the unit? As a hunch, I'd guess it probably rectifiers, filters and regulates it to DC. I bet trying to make something that can provide that DC power will be easier than making an isolated AC output.

[PRR]

> xp100 can handle a square wave or if it needs a sine one

Some things work grossly better with squares; but in audio, squares are BAD.

And if talking 50Hz, "some ferrites" is not enough to slow 50Hz squares, they are just enough to reduce MHz interference.

It surely expects "wall power", a sine with few harmonics.

You also have to account for the different ways we measure/specify squares and roundy-waves. Which further depends how the input is rectified and smoothed. Common peak-catcher rectifiers charge near 1.414 of the RMS value. Choke-input systems charge to 0.9 times RMS. Systems with much resistance can be anything from 0.01 to 1.4. And then there are Doublers.

> 9v dc to 9v ac @ 500ma
> LM386 feeding the transformer

9VAC at 0.5A is 4.5 Watts.

No way a '386 will deliver 4.5 Watts.

> Any one tried this before?

Yes, except it was a 5 Watt motor. With various losses, a 20 Watt amplifier did the job, some lesser ones didn't.

And unless a XP100 has motors, it surely eats DC internally. An AC wart often means they run a voltage doubler center-grounded to make both +12V and -12V DC. 5V-> +/-12V modules are commodity parts, though 4.5 Watts is the high end of the low-cost models.

[SISKO]

What does the xp100 do to the AC inside the unit? As a hunch, I'd guess it probably rectifiers, filters and regulates it to DC. I bet trying to make something that can provide that DC power will be easier than making an isolated AC output.

It makes a bipolar power supply inside of it, thats why i tought of and isolated power supply in order to avoid ground loops.

a 20 Watt amplifier did the job, some lesser ones didn't.

And unless a XP100 has motors, it surely eats DC internally. An AC wart often means they run a voltage doubler center-grounded to make both +12V and -12V DC. 5V-> +/-12V modules are commodity parts, though 4.5 Watts is the high end of the low-cost models.

A 20W amp is far to big for what im thinking, i´d rather use a separate transformer.

Im gonna try a 555 charge pump (from here http://www.diystompboxes.com/smfforum/index.php?topic=80007.15; ) for the negative supply rail and hope that it wont heterodyne with anything and to get enough current out of it. The bipolar power supply seems to be only to feed the analog section of the pedal.