Using diodes to isolate a noisy tuner? (A/B/Y Switchbox)

[Ryan Trevisol]

Hey guys, I've searched all over the internet and in these forums but I can't find an answer (or even a situation like this).

I've got a noisy tuner pedal, a Fender PT-100. It seems to throw some kind of crap noise (sounds like rapid, random, electronic beeping) into the signal. To try to remedy this, I tried plugging it into an unused stereo output of a chorus pedal, like a dead end, but it still puts noise into my signal.

So I'm building an A/B/Y box tonight and I thought, wouldn't it be cool to split the signal off to the tuner inside the switchbox? Then I realized, if the noise is coming back from the input of the tuner, it would probably be just as noisy this way.

So I thought about it, and I thought about the electrical properties of diodes. They only let current flow one way. Couldn't I just use two diodes to isolate the signal as it goes from the input of the switch box to the input of the tuner? Would that work?

Now, I realize that the issue might be that the tuner is just throwing out so much EMI that the other pedals are picking it up and amplifying it. In that case, I need a new tuner. So when I ask, "will it work" I mean, electrically, would signal get through the diodes to the tuner, and prevent any potential backflow of "signal" going the opposite direction?

If it would work, what kind of diodes would you suggest?

[R.G.]

Sorry, that will probably not work the way you envision it.

What you want is a buffer to take your guitar signal and send it to the tuner. A buffer is a one-way street for signal. Signal goes in the input and out the output, but can't go back the other way very easily.

Unfortunately, it is also possible that the squeel is coming back through the +9V or ground lines to the tuner. Is the tuner running on a battery or a shared power supply with other pedals?

[Ryan Trevisol]

Okay, too complicated for a PCB-less ABY box.

It may be coming through the power supply, in fact I'd say it's likely. The supply I"m using is a wall wart running an SKB board like this:

Which is crappy. I know it's crappy, and I'm working on fixing that.

This is just stage one of a 3-stage FX revamp for me:
1. ABY Box /Recombiner
2. Double-Decker pedalboard (I'm building it tomorrow)
3. A proper power supply (will build in the coming weeks)

Along those lines, I was thinking about using this circuit:
http://www.generalguitargadgets.com/diagrams/ultra_clean_ps_lo.gif
With a 2-amp transformer to provide 8 or 9 9V@250ma outputs.
I'd be open to suggestions of another Power supply that's known to be quiet and scalable.

[R.G.]

Any linearly regulated power supply  will do that.

The Boss PSAs will do it.

Full disclosure here: I work for Visual Sound. I mention this not so much in advertising as because we have lots of field history of the $25 1Spot running pedals from one to more than you'd ever want, quietly and effectively. I know that one works. But for your setup, unless you just want to build a power supply, any one of several regulated adapters will work. Unregulated adapters are known for introducing hum and noise.

Best advice: go try out some regulated power supplies in a music store. Pick the one you like.