My friend has an acoustic-electric bass. I can get you more specifics tomorrow, but for now just accept that it's a standard issue acoustic bass guitar (not upright) with an under-saddle piezo pickup, 9V driven preamp, and 3 band EQ.
For a while now he's been complaining that it's flaky. He can't trust it for live performance. "It's the jack," he says. It buzzes and makes noise and drops out all the time. Well, if it is the jack, it's an easy fix.
So I was at his house this evening and asked him about it. He unscrewed the jackplate and I took a look. All three solder joints looked and felt pretty solid.
"Yeah, it looks good but here," he said, handing me a cable. We were in his living room. The cable he handed me was attached to the bookshelf stereo he uses to amplify his computer. On my end it was an 1/8" TRS plug adapted up to 1/4" TRS.
I brought it home to check it over, but I'm pretty sure I know what the problem is.
The cable works perfectly fine with his (passive) electric bass. Yes, the level's probably a little low. The impedance mismatch actually seems to roll off enough treble to act as a half-butt speaker sim.
The preamp on the acoustic quite likely has low enough impedance and plenty of gain to get a good healthy signal into the stereo.
Last Edit: May 18, 2010 13:22:11 GMT -5 by ashcatlt
Well. to make most electro acoustic guitars work needs a mono 1/4" plug, to short the battery negative to ground to make a circuit. A stereo plug, with a ring, would not work, or maybe intermitently depending on exact dimensions. Any good?
I had thought about disqualifying a number of board regulars from the competition, and JohnH was at the top of that list. That's exactly what I figured was the problem.
Unfortunately, that ain't the problem. It was enough to render last night's test invalid. I just plugged in a mono plug, though, and did in fact find that it makes a nasty noise and cuts out occasionally if you wiggle the plug. You almost have to try to get it to mess up, but it's there!
To make sure it's not just a flaky cable, I tried several of my guitars. Unfortunately, both of my basses have a very similar problem. My main gigging guitar (my Strat) doesn't, though. Couldn't get it to happen no matter how I jiggled or jostled or pushed on the plug.
In the case of the bass in the original question it might well just be corrosion/oxidation on a very old jack which hasn't been used much. I'd bet we could probably cure it with some contact cleaner and about a hundred plug-in-plug-out operations. Easier to just replace the thing, I think.
I'm sure one of those two can explain it more clearly.
No need, you got it.
It's true of the input jack on most stompboxes as well. You could do a quick google for just about any pedal schematic and look at the input jack portion to get the idea.
I have a number of short TRS cables meant for balanced connections on my studio patchbays. They look almost exactly the same as the cables I use between my pedals. It's only just recently that I figured out why they did not work for that application.