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Post by ashcatlt on May 18, 2010 1:35:37 GMT -5
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.
Anybody wanna lay bets?
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Post by sydsbluesky on May 18, 2010 12:47:16 GMT -5
Wouldn't a stereo want to see a line level, anyway?
But yeah, cable is always the very first thing to check whenever I see something like that. That's my bet. Can't trust those adapters for anything.
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Post by ashcatlt on May 18, 2010 13:21:16 GMT -5
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.
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Post by ijustwannastrat on May 18, 2010 13:27:10 GMT -5
Was the jack simply bent out of shape? I say always put in stereo jacks, for future fun, and to keep things straight.
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Post by JohnH on May 18, 2010 15:53:33 GMT -5
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?
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Post by sydsbluesky on May 18, 2010 16:50:13 GMT -5
Well... my next guess has to do with the stereo jack, then. Are the contacts not lining up properly?
EDIT: Guess I'm not the first with that one.
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Post by ijustwannastrat on May 18, 2010 20:04:07 GMT -5
I have read the last two posts multiple times, and I have no idea what's going on.
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Post by ashcatlt on May 18, 2010 20:25:49 GMT -5
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.
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Post by ashcatlt on May 18, 2010 23:22:05 GMT -5
It was the jack.
Holding the hack in one hand. Plug cable in with the other. Wiggle the plug around and you can feel the slop and watch the resistance jump around on the meter.
New jack. No slop. No movement on the meter. Soldered it, plugged it in to listen. I can't make it cut out.
It still won't work with a stereo cable inserted.
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Post by sydsbluesky on May 20, 2010 16:25:53 GMT -5
Strat
I think I understand what's going on, here.. I'll try to explain.
The introduction of the 9v battery in an active system uses a stereo jack but isn't a stereo output... it's just a battery shorted to ground, as John says.
This is an issue when using a TRS (tip, ring, sleeve, I think) cable, because you're not sending the battery to ground(sleeve), as would happen with a mono cable. You're sending it to the ring.
Think of his jack not as a stereo jack, but as an active jack, maybe... I'm sure one of those two can explain it more clearly.
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Post by ashcatlt on May 20, 2010 17:26:59 GMT -5
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. |
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Post by ashcatlt on May 20, 2010 17:27:43 GMT -5
BTW - He played it on-stage for a half hour last night with the new jack and no problems at all.
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Post by sydsbluesky on May 20, 2010 20:18:55 GMT -5
It's always nice when it's a jack.
An even cheaper fix than buying a new cable.
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Post by sumgai on May 21, 2010 2:17:00 GMT -5
sbs, I'm sure one of those two can explain it more clearly. If I tried to explain it any more clearly, I'd be going in reverse, and confusing everybody. You earn the daily +1 ;D Better watch out - before you know it, newbies are gonna consider you a "person of knowledge".  sumgai |
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Post by sydsbluesky on May 21, 2010 6:40:31 GMT -5
Newbies are built to be wrong, so they may as well be wrong about me!
Especially since I specifically remember one of those points being from you for what was - let's be honest - a poop joke.
(August 14, 2009)
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Post by sumgai on May 21, 2010 12:45:49 GMT -5
syd, Newbies are built to be wrong...... Oh? Then would you care to comment on this particular post: hi Sumgai,
you joined up, and started giving advice, rather than asking for help.
so, i guess nobody noticed you were new to the forum.
so:
WELCOME ABOARD!.......... Some days my Ginko Biloba trumps your whippersnapper memory! ;D (Just wished to Gawd that they weren't so few and far between!   ) sumgai |
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Post by sydsbluesky on May 21, 2010 20:08:47 GMT -5
Lemme know if you get a muscle cramp from patting yourself on the back, eh? |
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Post by sumgai on May 25, 2010 1:51:30 GMT -5
Lemme know if you get a muscle cramp from patting yourself on the back, eh? Why, are you a masseur? Sorry, my health insurance doesn't cover that kind of traveling money! But thanks for asking! ;D sumgai |
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