Amp: can something be done with unused 5V tap?

[elberto]

So I'm in the process of putting an amp together, and I'm wondering if there's something creative I can do with the unused 5V tap coming off the power transformer (using a ss rectifier for the amp's b+)?  Could this be used to power, say, an onboard effect with some rectification and filtering?

[nelson]

Maxon voltage doubler bring it up to 9v an use it to power any onboard effect you would like, personally I would go for a simple tremelo (EA tremelo) rig it up with a simple relay or fet switching and use standard amp switching to switch trem off/on.

May get added noise with the MAX1044 though.

Thats what I would prob do, there is bound to be a better option than the 1044 though.

[putrefusion]

make it switchable rectifiers... 5volt tube rectos are easy to come by.

or, drill some more holes for 12ax7s and add channel switching, using relays and vactec LDRs

[elberto]

next stupid question:  exactly how do I get 9vdc from 5vac again?  

I def like the idea of sticking a trem in there.

as for channel switching, I'm using one of those weber relays that runs off the filament supply.

[Paul Perry (Frostwave)]

If that 5v winding is not connected to anything else, you can make a simple diode voltage doubler like this: (the top one)
http://webpages.charter.net/dawill/tmoranwms/Circuits/Doublers.gif
Allowing for diode drops, you might get about 10v DC or so from this.
Maybe (check data sheet) you could run a low dropout 9v regulator from it.

[nelson]

If that 5v winding is not connected to anything else, you can make a simple diode voltage doubler like this: (the top one)
http://webpages.charter.net/dawill/tmoranwms/Circuits/Doublers.gif
Allowing for diode drops, you might get about 10v DC or so from this.
Maybe (check data sheet) you could run a low dropout 9v regulator from it.

Nice!

Knew there had to be somethign better than a charge pump.

[Paul Marossy]

I was also going to suggest a voltage doubler circuit, but then I thought about it a little bit - wouldn't you end up with a positive and a negative voltage instead of a positive voltage and ground?

[Paul Perry (Frostwave)]

I was also going to suggest a voltage doubler circuit, but then I thought about it a little bit - wouldn't you end up with a positive and a negative voltage instead of a positive voltage and ground?

Well no, if the transformer winding isn't connected to ground.
It is true, that if you make the non-diode side of the transformer winding ground, then yes, you have a +5 and a -5 output, with respect to that ground.
But, if you don't connect the transformer winding to anything, then you have the two output caps, and they just stack like a pair of batteries end to end, and you make the - of the - cap ground, and there it is!!

[Paul Marossy]

Oh, I see. That's cool!  I only asked because I have very little experience with voltage doubler ciruits.  :wink: