Why exactly does the series mode hum?

[Temcat]

Hi,

I got tired of the hum from my my MIA G&L L-2500, which for some reason became louder recently, and shielded it with GRAPHIT 33 graphite paint. In addition, I implemented star ground, with the jack's GND terminal being the grounding point.

As a result, the hum got significantly quieter with parallel mode, but not so much with series, which is still fairly noticeable. BTW, my bass doesn't have bass boost caps, so I don't get why exactly it should hum. Any ideas?

[sunbeast]

It shouldn't hum in series (without the capacitors) as long as it is wired correctly- series will tend to be louder though, so it may raise your noise level slightly. You're sure you cdon't have the bass boost caps? If you can't trace it to anthing else, you might want to trace and test the wiring with a multi-meter and tap the pickup poles to make sure everything is working as it should- my L2500 was wired wrong from the factory (the yellow wires from the pickups were switched- the neck wire to the bridge part of the switch and vice-versa). It didn't cause any excess noise- just some weird coil configurations (which was incidentally what originally turned me on to the idea of modding G&Ls coil switching).

Karl

[Ken Baker]

Originally Posted by Temcat

I got tired of the hum from my my MIA G&L L-2500, which for some reason became louder recently, and shielded it with GRAPHIT 33 graphite paint. In addition, I implemented star ground, with the jack's GND terminal being the grounding point.

Is the noise a more-or-less clean humming sound at AC line frequency (60Hz here in the USA) or more of a higher-pitched and somewhat dirty buzzing sound?

If it's a hum, check bridge ground, your cable, and the bass' jack. Also check your amp's grounding.

If it's more of a dirty buzz, back off the volume control on the bass to between 50% and 75%. Obviously, this assumes that you have the control cranked all the way up, which is normally to be avoided with G&L L series basses (in active or passive mode) or ANY active bass. Check your amp's grounding here as well.

Ken...

[Temcat]

Originally Posted by Ken Baker

Is the noise a more-or-less clean humming sound at AC line frequency (60Hz here in the USA) or more of a higher-pitched and somewhat dirty buzzing sound?

If it's a hum, check bridge ground, your cable, and the bass' jack. Also check your amp's grounding.

If it's more of a dirty buzz, back off the volume control on the bass to between 50% and 75%. Obviously, this assumes that you have the control cranked all the way up, which is normally to be avoided with G&L L series basses (in active or passive mode) or ANY active bass. Check your amp's grounding here as well.

Ken...

It's a hum, and I've checked everything. Most of it remains in the passive mode. After visiting a couple of rehearsal places, I came to the conclusion that the residual is most likely due to the amp and its grounding. Though we're well into the XXI century, grounded wall sockets, especially in residential houses, are not that common here in Russia. Signal-to-hum ratio at my home is quite worse than at either of the two venues, the bass was fairly quiet there.

Also, it's quite possible that hum increase in the series mode is due to it being louder. When I turn down volume to get about the same volume level as in series, hum level gets very similar to that in the parallel mode.

My general conclusion is therefore that the shielding was successful :-)

[sunbeast]

I have had similar grounding problems at the majority of houses I've lived in the US over the last 10 years, so you're not alone there! If the outlet is not well grounded, shielding tends to lose a great deal of its benefit! In my current house, all my instruments function more or less like radio towers in single coil mode- by far the worst of any house I've ever lived before...

Karl