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Wallwarts?

Started by tcobretti, August 11, 2006, 02:22:12 PM

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tcobretti

I'm a diystompboxes regular who is trying to branch out.  I searched the forum but couldn't seem to find the answer to what seems like a fairly obvious question.  So, either it is so stupid no one bothered to ask it, or it has been answered and my searching skills suck.

Ok, so I wanna build an LM1875 based amp.  Will a 18v wallwart power it?  Is there a reason not to use wallwarts with chipamps?

joecool85

The biggest reason I can think of is lack of amperage.  Although, the voltage would be a problem two.  18v ww would only give +/-9volts, way too small.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

tcobretti

Ok.  I see your point.  For the sake of my continued education, if I were to find a 40v wall wart (yeah, it's ridiculous), it would make +/-20v DC right?  How would I wire it to the circuit?  In my limited experience, a tranny has 3 wires while a wall wart just gives you + and - right?  If we consider the schem -



Where would Vee and Vcc come from if one was using a wall wart vs. a tranny? 

I really appreciate your patience; I can't seem to get my head around this power supply stuff.

Crystallas

A wallwart with the desired spec is fine. As joe said, amperage is what you should also be looking at, and aslong as your in spec, you'll be okay. I particularly like laptop adapters to find a decent quality shortcut to building a PSU.

joecool85

You would need to wire it into a powersupply section of a board that would go from positive 40v, negative is ground, to +/- 20 with a middle ground.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

tcobretti

Ok.  Thanks for the help, I understand it a little better now.  I'll probly have more questions soon.

Thanks again.

idle_chatterbox

QUOTE:
" For the sake of my continued education, if I were to find a 40v wall wart (yeah, it's ridiculous), it would make +/-20v DC right?"

I wouldn't say ridiculous. I have a 30v, 500ma one that I scrounged from a discarded inkjet.

Recently, on the DIY stompbox forum, there was a guy talking about modding a 30v (or possibly higher, I don't remember) power adapter. I don't know if he ever finished the project, but it sounded interesting to me, since my adapter just sits in a drawer. Maybe if you searched on that forum you could turn something up. Not long ago on ebay someone was auctioning about 10 adapters, and I remember some were fairly high voltage. So I'm sure they're out there.  :D