? Using a 12V DC Power Supply in an 18V Stomp

[Jerry Overstreet]

I have an old Ibanez AD80 delay box that has 2 9v battery holders, but since it had a voracious appetite for batteries plus the battery connectors and wiring went south, I've been powering it with a 12V DC adapter for more than 20 yrs. I have no way of knowing whether the PS I'm using is regulated or non.

I've had no problems doing this, but I have a couple other units with the same requirements.

Other than the obvious should use the proper voltage PS, in cases where such adapter might not be available, what problems and/or differences might occur with using an underpowered PS?

[Donny Hinson]

Some units will work fine with less voltage, and some will not. It won't cause any damage to underpower because that's a normal occurance when batteries run down.

However, if the power supply cannot supply enough current, the unit may malfunction, or the power supply itself might be damaged.

[Mike Auman]

In addition to Donny's comments: if everything sounds OK, the only down side is reduced headroom (the level of clean signal that can be passed before the pedal starts to distort.) 12V power will give you about 2/3 of the headroom of 18V power, so a hot signal will distort quicker at 12V.

[Jerry Overstreet]

Just for fun, I measured the static voltage of the unit which I probably did before I put it in use....but it's been over 20 yrs...it is something that I likely would have done.

Anyway, it measures 16.2 volts. Since it's stamped 12V ouput, I doubt it is a regulated adapter, but I don't know. It is an NEC adapter that I have reversed the polarity by swapping the wires to the connector.

Over the years, I have acquired a few power supplies and tend to utilize them when I get a new or different device where one is not supplied. [Just have to observe whether AC or DC output and polarity along with sufficient amperage requirements.]

I have noticed that many times, they will measure more voltage than is noted on the case.

Obviously, I prefer to use the mfg. supplied PS if available as I have seen operational issues with some that are not.

[Scott Swartz]

For the single specific case of the AD80, there is a MC78L12 12 volt regulator IC on the PCB, so any supply of 15-20 VDC regulated or not will work fine.

[Jerry Overstreet]

Ah...I see. Learning something new. I hadn't considered a stomp box or other device might have it's own internal regulator.

So that's one of the reasons the mfg. states use their specific power supply, I guess.

I posted earlier about a device with AC output wouldn't activate a certain function even though the generic power supply had the proper voltage and amperage. My tech had to convince me by going on his own and acquiring the proper adapter.

Thanks for the info Scott.