Making a 9V Pedal 18V

[WJR]

Hi,

I am interested in putting an internal transformer in a circuit to change the input voltage from 9 to 18V to give it more headroom. Do i need to change anything on the circuit board ie double resistance values to cope with this double voltage, or do i just have to check for example that all parts like capacitors for example have been rated for usage over 18V>

Any help appreciated,

Cheers,

Will

[MartyMart]

The reisitors will be fine, just make sure your caps are rated a bit higher, I would use 35v electro/tants and lots of poly caps are 50-63vrange  anyway, MMK  AVX etc.
Double check any op-amp ratings as well and you're good to go.

Marty.

[WJR]

Cheers mate, my 350V caps should do fine then hehe

[toneman]

Doubling the V will *not* change the gain of an opamp.
Gain 4 an OA is set by the resistors in the neg feedback loop.
If it's "just" trannys,  U might have to adjust /rebias.
I would use an adj pwr sup & raise the V in steps,
while feeding a signal in.
U might want 2 watch 2 Cwhat the new current draw is.  
An adj, regged pwr sup would allow this.
A scope & sig gen would B what  I would use....
stayUP
tone

[WJR]

Ok, now you have turned what was meant to be a simple thing into a whole new complication. I cant find any information anywhere on the web on how to bias a tranny - can anyone help me ?

[MartyMart]

Have a read of some projects at www.runoffgroove.com
Lots of their transistor circuits, like the "Odie" and "English Channel" are biased, with resistors to run at 4.5 v at the "Drain" of the transistor eg on a J201, and you will have to make some adjustments to those resistor values if you want to run the pedal on an 18v supply !
If you need some detail, just do a "biasing transistors" type of search, you'll find a lot of posts and some more answers too.

Cheers,
Marty.

[KORGULL]

You might want to try this://www.diystompboxes.com/pedals/vdbl.html

[Paul Marossy]

One thing to keep in mind is that although you may increase headroom by running it on 18V vs. 9V, the noise floor may also significantly increase, too. Depends a lot on the type of circuit.

[Mike Burgundy]

Don't be offended, but just to be sure: this pedal has AC power, not a battery right?

[Paul Marossy]

just to be sure: this pedal has AC power, not a battery right?

Oh yes, good point. An internal AC transformer would need a rectifier and filter caps if the circuit in question runs off of a DC voltage...