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Double Bass Ground Hum

Jeff Schwartz

Jeff Schwartz

Jun 9, 2005
72
11
58
Los Angeles
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#1
What gear and tricks have you found best for avoiding ground hum problems? Especially playing musicals, I've found amp hum to be a problem. I played a Cremona and now have an old carved flatback. I used a K & K Bass Max on the Cremona, then switched to a Realist, which I put on the flatback when I got it. For amps I've used a SWR Workingman's 10, which was way too noisy for theatre gigs (and two amp repair shops could find nothing wrong with it), and a Kustom 1x10 combo (don't know the model), which is a little better. I've used a Raven Labs MDB-1 in front of the Kustom to enhance the tone & to facilitate doubling (and yes, the hum is a problem with my bass guitars too. I expected that with the Danelectro, but with a Carvin Jazz-style fretless?).

One guitarist suggested I get a line conditioner. He uses one to make sure his tube amp gets driven consistently. I'm not sure how much it'd help with noise. Is the answer a high-end amp like AI or Walter Woods? Are they more noise-resistant? What do y'all do?

Thanks!
 
#2
:hmm: Need some more information here. Does the hum happen everywhere you play, or just in the theater? Is it more audible in some places than others? Is it that light ,annoying high frequency hum, or that low frequency power hum? Whenever I play a theater gig, or a high volume job, I use a power conditioner just in case, but I haven't had a problem for years. ( But I use a WW and an AI Focus as my two main Amps;) ) Anyway, there are many variables that can contribute to hum. Fluorescent lites, Dimmers, computerrs, all kinds of stuff. One fix I used to use was a ground lifter.( That plastic thing that turns your 3 prong plug into a 2 Prong) I'm sure you've tried the ground lift switch on your amp.
Also it could be a shielding problem .Have you tried different cables?
 
#3
Tried the ground lift switch and the 3-2 prong thing. Some cables are worse than others, but none are good. Maybe better shielded cables are the answer?

Theaters are the worst (I'm sure it's the lighting system, plus the hum is really obnoxious in the non-music parts of the shows, while people don't even notice in a bar) but it also happens at a couple of homes I jam at (older wiring?). Most places are fine.

When you say "power conditioner," are we talking about one of those rack light deals, or something more elaborate?

Thanks!
 
#5
Some low cost dimmers can generate a lot of RFI. But It is not likely to be rfi coming down the power line, getting to your amp, and coming out the speakers. It's more likely your input signal to the amp picking up the rfi from bad shielding. A power conditioner won't help. Or anything less than $500 wouldn't help.

The realist has a foil shield, so how about checking with an ohm meter that you have a good shield to ground connection from this foil shield.

It could be the realist isn't matched impedance wise to the input of your amp. This can make you turn up the amp high enough that noise from the preamp itself is contributing to the noise. Maybe try another preamp. Keep the preamp close to the pickup, and use a balanced cord from the preamp to the amp - if the amp has balanced ins.

Or maybe try a noise gate. I never found one fast or sensitive enough for musicals. Or maybe just a mute switch you could mute between numbers?
 
#6
While I've never played in a theatre, I have done sound in them. If your tech guys are smart they will make sure all the audio gear is plugged in on a seperate circuit from everything else, so you won't be getting any hum off lights etc. If you're not currently doing this, bring it up or try it yourself.
 

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