Careful With That PSU, Eugene!

I had an interesting "thing" at rehearsal last night. The pedals all sounded a tad weird, and things came to a head when I found that just the analogue delay section of my EHX Tone Tattoo didn't work at all. The straight through clean signal was there, but no delayed signal, and turning the mix right up (so you would normally just get the delayed signal) meant no output.

So I was miffed. Peeved, even. Another £150 down the drain, and I'd just spent out on a new heavy-duty music stand and a lovely new Hercules mic stand.

So I finished rehearsal in a bad mood and didn't play well because I kept wondering what could make just one section of the pedal fail. So at the end of rehearsal a very-narked Screaming Dave grumpily removed the pedal from the board with a view to performing some sort of autopsy on the morrow.

And then grumpy Screaming Dave happened to glance at one of the two wall-warts he uses to power said pedal board. The one with the switchable voltage - and it's set to 12V. My immediate thought is that I've fried something in the Tone Tattoo, but I reassembled it into it's rightful place and fired the rig up again and, lo and behold, it works fine!

I've read a lot on other forums about running pedals at higher voltages, which I'm sure is OK with some, but my cautionary tale is to be careful. Some might not work at all ....

But, my question to you honourable gentlemen is, why would too high a voltage stop it working at all? My first thought was that an op-amp had gone belly-up, and that would seem to fit the symptoms, but why would too high a voltage cause an op-amp to just not work?

Answers on a postcard, please ......


  • LesterLester Posts: 1,619Member, Moderator
    Jocko is the electronics expert; he will know the answer.
  • MegiMegi Posts: 7,116Member
    All too easy to make this kind of mistake - I've done similar things myself with my pedal board and it's power supply, although in my case I had two of the outputs selected to too low a voltage. Like you, for a while a got in a bit of a cross mood, and blaming the pedal manufacturers, rather than myself!

    Glad all is good though Dave, and afraid I wouldn't know where to begin re answering your question. Although I can say with confidence that "it's something to do with the electronics" - hope that helps. :D
  • JockoJocko Posts: 7,009Member, Moderator
    Pedal may have over-voltage protection. The 12v output isn't opposite polarity by any chance?
  • Screaming DaveScreaming Dave Posts: 779Member
    The over-voltage protection is an interesting notion, but it was just that section of the Tone Tattoo the didn't function correctly. The Nano-clone and Metal Muff bits of it worked (albeit not properly. The chorus was nowhere near as lush as normal and the Metal Muff was just yuk.)

    The 12V output is the same, it just has a switch which changes voltage. Also, it powers all the pedals bar the Rat (which does have reversed polarity) and they all functioned in one way or another.

    One thing that just occurred to me is that maybe the adaptor is faulty and actually delivers less than it should when said to 12V. I must do a test. Maybe it saved my bacon (from being fried!)
  • Kevin PeatKevin Peat Posts: 3,090Member
    As it happens my Mum bought me an electric razor for my 13th. I turned what I thought was a battery cover, couldn't get it off and so left it. Mum asked me to show her how the razor worked - I plugged it in, started shaving and the thing began to melt in my hands with smoke and everything. She was in tears. It had cost her a week's wages.
  • Screaming DaveScreaming Dave Posts: 779Member
    I was brought up with the received wisdom that if you put the wrong voltage up something it will catch fire, explode and kill you. Seems designers are much more canny these days at stopping that happening. Whatever happened to the good ol' days, eh? Life was much more interesting back then!
  • Kevin PeatKevin Peat Posts: 3,090Member
    Grandad sorted it. He put the voltage changer in its right place and took it back to the shop with its receipt and got a new one. Knowing what I do now about production engineering that would have caused a real stir at the research department of Hitachi.
  • ESBlondeESBlonde Posts: 894Member
    Digital circuits tend to behave far more eraticly with over or under voltage. I sometimes run a small generator for a sound system at village fete type things and CD players or Digital crossover units are susceptable all kinds of rubbish. I run a voltage stabiliser between genny and power sockets to clean up the voltage.
  • Screaming DaveScreaming Dave Posts: 779Member
    Digital stuff is particularly susceptible to spikes and other "unclean" features of the power supply, it's true, but the Tone Tattoo has an analogue delay section. So not sure what was going on with it, but it seems OK now. Interestingly, I had a Carl Martin Red Repeat which was purported to be an analogue delay, but I later found out was a digital recreation of the analogue delay characteristics. That stopped working, too, but I never found out why. Getting wet in the rain at a gig probably didn't help!
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