Some way to rig up 12v AC?

[Harry Klippton]

Some time ago, a friend passed me an outboard effects unit to test and see if it worked, but he didn't have the power supply. The unit says it requires 12v AC. Is there some way I can rig this up without buying a 12vAC wall wart?

 

[Erik S]

Always be hoarding wall warts!

I’ve got some pc speakers that run on 12AC

 

[BuddytheReow]

If you've got a 18V adapter, you can always jerry rig it with a 12v regulator. Or make a voltage divider?

 

[Harry Klippton]

If you've got a 18V adapter, you can always jerry rig it with a 12v regulator. Or make a voltage divider?

AC my guy. AC

 

[BuddytheReow]

AC my guy. AC

Then just a voltage divider. I don't see why that wouldn't work if you're really in a pinch

 

[Erik S]

Time to get a variac!

 

[Harry Klippton]

Time to get a variac!

I thought about this. Even with a meter to monitor that I'm not exceeding 12v, this seems risky

 

[Erik S]

You still wouldn’t want to bump the knob, but that would slow the current down at least. This one seems to hold a fairly steady voltage.

 

[chris.knudson]

Maybe something like this would work...a 120V to 12V transformer.

 

[chris.knudson]

Oh never mind, this looks like 120-12V DC

 

[chris.knudson]

Maybe this instead...

 

[xefned]

You have a 12v DC power adapter? I suspect that would still work.

 

[chris.knudson]

You have a 12v DC power adapter? I suspect that would still work.

That was my first thought, but he needs 12V AC. I think a transformer is the way to go.

 

[owlexifry]

an 12VAC wall wart would probably be cheaper than a mains (120V?) transformer with 12V AC tap.
but hey if you can find a transformer for less, do that.

 

[Harry Klippton]

I'm gonna have to open it up. The polarity isn't marked on the chassis either so I'm gonna have to do some snooping

 

[Robert]

It's AC, there is no polarity.

If it requires an AC power supply it's very likely generating bi-polar supplies in the effects unit.

Even if not, full-wave rectification would be producing a DC voltage higher than 12V from a 12VAC input (around 17VDC)

 

[chris.knudson]

The one I posted a picture of above is $16 on Amazon.

 

[Harry Klippton]

Thanks @Robert


I've been meaning to ask and this seems as good a time as any. How do bipolar power supplies work and what's their purpose?

 

[benny_profane]

Thanks @Robert


I've been meaning to ask and this seems as good a time as any. How do bipolar power supplies work and what's their purpose?

Do you mean how do circuits deal with AC power or how bipolar DC input works?

 

[JTEX]

If it requires 12VAC, it almost certainly uses single wave rectification (1 diode per polarity) to generate dual rail DC. Pretty clever and efficient. You just need a simple 12V transformer. No DC power supply will help.