Goood Morning Vietnam!!!!

[Buzzy Fretts]

S'ok. This is one for the electronic gurus out there who might tinker with keyboards and PAs as well as guitars.

I've noticed recently that when I plug my MIDI woodwind controller and little half-rack sound module into a PA etc that I have become a radio. Depending on the impedence setting on my channel the ghost in the machine might be a background bustle or a full blown in_you_face broadcast. This has happened three out of three times the last three times out so I am quite sure it is me. The reason I needed three times to be sure is that after I turn off and unplug, the radio ghost stays in the system for 5 or 10 minutes.

Any guesses what is going on here and how I can troubleshoot it? I am planning on trying the controller with a differtent module- and the module triggered by a keyboard- to isolate it further. After that I am at a loss.

[Jeff R]

Don't know if this is related but about four years ago I was recording a song with a stock strat, a Boogie Rectoverb combo in hi-gain mode, a wah pedal and a Phase 90, and everytime I switched on the wah, I started picking up this Spanish talk radio broadcast that had one of those whistling short wave hum frequencies. I would rock the wah and I could wah the broadcast and manipulate the hum all kind of weird ways. Then when I clicked the Phase 90, it was phasing too and overexaggerating the "click" when the phase circuit would repeat.

Ended up using it as the intro for the song. Never was able to get it to happen again despite several tries.

[Cary]

If Jeff's suggestion doesn't help, try some aluminum foil.

[Buzzy Fretts]

Thanks Jeff. I am the master of found art. The things that have found their way into my "productions" are many and varied. I had a blast back when I used to produce sky shows for the planetarium. The toilet flush mixed into the black hole sequence was typical. You'd never actually ID the sound but something in there got_you_thinking.

Cary thanks for the reminder. There's a few "conehead" stories I could tell from my college days that involved one or two boxes of renolds wrap. These are stories I could tell. But I won't. :angry:

[Guest cruster]

Maybe the lead for the wind encoder is acting as an antenna. I suppose you could try some ferrite beads, or you could make a choke coil (if you're not going too far from that tone generator, do about 1/2 dozen turns in the lead to the controller, maybe about 4-6" diameter). Figure out where the RF is leaking into the chain and then go from there. Do you get the radio if you unplug the wind encoder? Is it the leads from the TG into the PA?

[Buzzy Fretts]

Hey Cruster. All good questions. I'm going to tackle this over the weekend and hopefully have a better handle on where the leak is occuring. It is common for an RF leak to remain in a sytem for a while after the offending devises have been disconnected?

[killerteddybear]

The problem you describe is a high frequency rendition of a ground loop (just like 60-cycle hum). Check your grounds, your cables, everything remotely electrical.

Remember that MIDI is designed to be electrically isolated (there are opto-isolators in your equipment to do that); but your system could still be part of a HF circuit if there are grounding issues between the components and/or the cable.

Some questions:

1. Are your wind controller and tone generator plugged into the same power bar (common grounded) or is the TG in the same power circuit as the PA?

2. When you 'unplug', what do you unplug from where? Start by pulling the audio cable out of the PA at the mixer (or whatever your entry point is) and shutting off you equipment; see if the broadcast remains.

3. Maybe it's in your PA mixer (I assume you plug into the same channel all the time). Switch your entry point or channel and see if the problem goes away.

4. Are you sure it's only your equipment? Try setting up before a gig and running the PA before you plug in your MIDI gear.

If you're sure it's in your gear, try this:

Add one piece at a time (first the signal cable into the PA {start with the levels down!}, then into the tone generator off, then turned on, then add the MIDI cable, then the wind controller off and finally turned on).

Good luck.

[killerteddybear]

I have no idea how I double posted this... stupid intrenet!

[Buzzy Fretts]

Thanks KT Bear. I had a feeling it might be a variation on that ole familiar issue. The problem has been seen in three different systems so its something on how my two units are talking to everything else. The wind controller is powered by the module (they are designed to be used together) so I fear one or the other has gone south. The unplug is complete. Afterwards the RF remains in the system for a 5 to 10 minutes. Weird.