first rule of preproduction: get rid of all your wall warts/daisy chains/midget-bicycle power stations and replace everything with 9V batteries.
but I never use batteries in anything live... one goes and your fucked... best thing to do is to try to plug the chain into the same power strip as the amp.
It depends on your power supply. Mine (a
Voodoo Labs Pedal Power 2 Plus) is transformer isolated (each output has it's own tap on the transformer), and it is extremely well regulated, so it is pretty quiet. These are, by their nature, expensive (lots of stuff in there), but it's a lot cheaper than a constant supply of batteries. Plugging the daisy chain into the amp's power strip is unlikely to fix this one, because there are (depending on how many pedals he has) quite a lot of ground loops going on.
To the OP:
You've got a ground loop. The signal is finding multiple paths to ground, and it's taking a noisy one. Those daisy chain pedal power things are almost guarantied to do this, and I have never figured out why anyone would sell them.
There are a bunch of things you could do. First, you could go to batteries, which would work every time, but it gets expensive in the long run and is horrendous for the environment (batteries have REALLY nasty chemicals). Second, you could go through all of the patch cables connecting your pedals, and clip the ground on one end of each cable, which will work most of the time, but sometimes it will cause a worse noise and you will have to swap out a cable which is grounded normally. Oh, and those cables won't work at all if you use batteries or a better power supply. Third, you could put out the money for a better power supply. Each output needs to be transformer isolated, and individually rectified and regulated, so it will not be cheap. The one I've got (mentioned above) is one choice - I would assume their are others on the market, but I don't know.
If you are REALLY comfortable with a soldering iron and building power supplies (they aren't hard, but the details ARE critical), you could even make your isolated PS. Weber has an appropriate transformer, which is pretty cheap, but by the time you get all the parts and do all the work you will not save much, if any, money. I only have one pedal drawing power these days - I do get power the LED's for my amp's footswitches from it as well - but I got it back when I was using more pedals and I think the isolated PS was WELL worth the price.
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