[sdiy] OT:Help with power problems

[rsdio at audiobanshee.com]

NEVER CUT THE GROUNDS FROM ANY POWER CABLE!!!

! ESPECIALLY NEVER CUT THE GROUND ON A POWER STRIP!!

(and while we're at it) NEVER USE A TWO-PRONG POWER ADAPTOR TO DEFEAT THE THIRD GROUND PIN!

Sorry for yelling, but this may save your life.

The ground is there to ensure that the circuit breakers trip when you start getting electrocuted. Electrocution probably only happens when something is wrong with the wiring in your gear or the venue, which is why there is an extra ground wire just to make sure that the circuit breaker will notice the extra current that is killing you and hopefully shut it off before you die.

No good piece of audio gear should connect the signal ground to the chassis ground or safety ground, at least not if is well designed. If you're going to cut any ground, then isolate the audio circuits (but that takes a bit of know-how, just ask the AES). There is plenty of gear out there that is designed poorly, but it's not worth risking your life to get rid of hum. Better to throw away the bad gear!

Look for papers by Bill Whitlock of Jensen Transformers. You'll get a lot of good advice about how to fix hum without risking death. Many of his writings are simple PowerPoint presentations that anyone can understand. If you want to dig deeper, he also has papers that a few audio electronics designers could learn a thing or two from. If you find something that's too deep for your skill level, just keep searching. Whitlock is the best resource for this topic.

Brian Willoughby


On Apr 20, 2017, at 6:04 PM, frey at radioles.com wrote:
> My performances involve signal processing the double bass or loops of the double bass. I use a furman pedal board that provides several mains and a bank of 9V for pedals. It also includes two built in audio buses. Plugged into a set of mains on this pedal board is another power strip that has 7 plugs that I have moon wall warts plugged into. I have noticed that if I touch the frame of the furman while patching a cable from my moogerfoogers I get a shock! I in fact have 120vac traveling between the audio patch cord tip or sleeve and the metal case of the furman power strip. The metal case is grounded. I am wondering if I should cut the grounds from the power strip chassis?
> I am a little clueless why this is happening at all. The moogerfoogers are only 9V dc and I assume isolated regulated power supplies? I will post some photo links if anyone decides to help. Thanks!
> Also, if this is too OT, please recommend where I should look for help. JoeF.