#1
I have a couple 9 volt 500mA DC wallworts (both are the same kind/maker) that if I use a multi-tester read 12volts DC. Would these be safe to use on my effects pedals ?
#2
is your multimeter on AC? it would make sense if it was, because it sounds like the 12 volts is a peak reading compared to 9 volts rms, if its on the wrong setting, that will mess up your reading
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#3
set my meter to 25 volts DC and on that setting it reads 12 volts dc. Its not a digital meter, its old school using a VU meter
Last edited by kidthorazine at Oct 23, 2011,
#4
make sure its calibrated right. other than that, i have no idea sorry
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Quote by Delanoir
In 60 years, there will still be Opeth.
You know why?
Death ain't got **** on Mikael.
#5
Quote by kidthorazine
I have a couple 9 volt 500mA DC wallworts (both are the same kind/maker) that if I use a multi-tester read 12volts DC. Would these be safe to use on my effects pedals ?


It sounds like its unregulated. With no loading it will deliver 12 volts. With 500mA loading it will deliver 9 volts. Loading in between those values gives you volts between 12 and 9.

Unregulated power packs like this are cheap and dime a dozen.

I probably wouldn't use it on my effects pedal.
#6
Quote by Phoenix V
It sounds like its unregulated. With no loading it will deliver 12 volts. With 500mA loading it will deliver 9 volts. Loading in between those values gives you volts between 12 and 9.

Unregulated power packs like this are cheap and dime a dozen.

I probably wouldn't use it on my effects pedal.


This. Most effects pedals are fine with a few volt difference though. Open yours up and check the voltage of the caps. If they're 16V+, you should be good unless there are digital chips that need +5V and the pedal doesn't use a regulator. Also be sure that it's a negative tip supply.
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#7
if it's an analogue pedal you should be fine. it'll sound different but it won't explode or anything. if you've got a digital pedal it will probably burn up.
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#8
Most likely it is 12V unloaded but drops to 9V with a load because it has no regulator. It most probably has quite a bit of ripple on it with a load. Calculate what resistor you need across it to get the rated current and place that across it (18 ohm to get maximum current, so go for a 22 ohm resistor). Then measure the voltage again.
If it reads the right voltage then it won't be doing any damage when plugged in but it's probably a noisy mongrel. If it's something like a tubescreamer that just has a few op-amps in it you could safely go as high as 15V before it fried (18V is the absolute maximum). If it's more complex and has digital components you have to be more careful.
To really know what is going on you'd put a load resistor across it and look at the signal on an oscilloscope. My prediction is that you'd see around 9V with a 120Hz ripple (60Hz if it's only half wave rectified). From what you've said I'd say you are looking at a badly filtered, unregulated piece of crap.
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Last edited by Cathbard at Oct 23, 2011,
#9
Quote by Cathbard
Most likely it is 12V unloaded but drops to 9V with a load because it has no regulator. It most probably has quite a bit of ripple on it with a load. Calculate what resistor you need across it to get the rated current and place that across it (18 ohm to get maximum current, so go for a 22 ohm resistor). Then measure the voltage again.
If it reads the right voltage then it won't be doing any damage when plugged in but it's probably a noisy mongrel. If it's something like a tubescreamer that just has a few op-amps in it you could safely go as high as 15V before it fried (18V is the absolute maximum). If it's more complex and has digital components you have to be more careful.
To really know what is going on you'd put a load resistor across it and look at the signal on an oscilloscope. My prediction is that you'd see around 9V with a 120Hz ripple (60Hz if it's only half wave rectified). From what you've said I'd say you are looking at a badly filtered, unregulated piece of crap.

hooray for knowing what all that means!!
Gibson SG Special Faded(Super Distortion/PAF Pro)
Carvin V3M
Jet City JCA2112RC
Taylor 114e
Ibanez SR300e

Quote by Delanoir
In 60 years, there will still be Opeth.
You know why?
Death ain't got **** on Mikael.
#10
After all that.....I still wouldn't use it on my effects pedal

You're better off with a regulated and well filtered output 9v power supply.

But that's just me.

At least now you're well informed to make your own choice
Last edited by Phoenix V at Oct 24, 2011,
#11
Quote by Phoenix V
After all that.....I still wouldn't use it on my effects pedal

You're better off with a regulated and well filtered output 9v power supply.

But that's just me.

At least now you're well informed to make your own choice


^^^This.
I get pedals in all the time for repair that people used these unregulated supplies. It really depends on the individual pedal if it will work well or not. If not, you can damage the pedal so be ready for that. They tend to not have good power filtering as they weren't designed for your audio pedal and they tend to introduce noise.

The best thing is to just use the proper power supply. It's better than breaking pedals. It will be cheaper in the end.