Powering 9v pedals with 18v???

[jeff]

I have dunlop dc brick and was wondering if it was safe to power 9v pedals with 18v. Any suggestions??

[jimi]

Some pedals might be ok and others won't. You would have to take a careful look at the circuit to see if it would be ok. Alot of commercial pedals have an 11 volt zener accross the power input so the first thing that would happen is you would blow that up if it has one and maybe the rest of the pedal aswell

[Rob S]

Why not build a cheap regulator for the 18V supply you have e.g.:

http://www.eidusa.com/Electronics_Voltage_Regulator.htm

Rob.

[Mark Hammer]

A great many op-amps and the vast majority of transistors are quite happy with 18v supplies. Sadly, that does not mean that one can automatically throw 18v wallwarts at them willy-nilly.

For instance...

1) CMOS chips do NOT like anything more than 15v, so a chorus or flanger that regulates a 9v battery down to 5v for the delay and clock chip might not do so for any other CMOS support chips (e.g., DOD uses a CD4007 for switching in the vast majority of their floor pedals), resulting in blown chips.

2) Although the cost and size difference is small these days, neverthless large manufacturers lean towards using the lowest voltage rating they can adopt on electrolytic caps. Often, that is 16v (next one up is usually 25v). Sixteen volts may be just fine for handling everything that occurs in a circuit piowered by 9vdc, whether battery or wallwart, or maybe even 12vdc. But 18v can either damage the caps or put them way off spec. That doesn't mean you couldn't first check the voltage ratings of caps in the pedal to see if they were okay and change all those that needed a rating upgrade. But it DOES mean you can't just lug the wallwart in and expect everything to work fine.

3) Sometimes pedals rely on the application of certain bias voltages at certain points of the circuit. Those bias voltages, in turn, are usually based on being a specific fraction of a known supply voltage, so fixed resistors are used to produce it. Radically changing the supply voltage may require all bias voltages to be reset in some way.

4) Some pedals, particularly discrete distortion pedals using germanium transistors, behave better when the supply voltage is lower.

So, while there may be a great many things that will happily tolerate the use of the 18v supply, and may well even perform better, don't expect EVERYTHING to hold up well or improve, and certainly make every effort to verify that the design and component ratings can tolerate such a voltage.

[Enzo]

PLUS: Power adaptors are rated at nominal voltage at FULL output current. At lower draws the voltage will be much higher. A 9v adaptor unloaded could easily be 16v. So that 18v adaptor could easily produce 25v at lower draws. That would be even harder on chips, caps, zeners, and whatever.

[jeff]

Thanks, everyone for the advice. Now I have real good idea of what to expect and look for.