GK MB150E distorting

[Birdbass]

Hey everyone,

I've had my GK MB150E for 2 years, have never had a problem with it, love the sound. I use an underwood pickup (using only one transducer on the low end) and typically have everything on the amp set to noon, with the exception of the hi-mid, which I'll usually roll back to almost nothing. My bass sounds great - like an upright, only louder.

HOWEVER- recently I've noticed distortion on the E string. It's frustrating because everything else is fine- woody, balanced, cuts through...then the E with distortion. Anyone else having this problem? Suggestions? Thanks!

[clink]

It could be your pickup. My RSII behaved the same way with my GK, so I replaced it. It definitely was the pup. OTOH, it is a slim possibility that you may have a problem with the send and return jacks. Run a cable between them to be sure.

[winston]

Clink's suggestions are good. Check the mounting of the pickup, and be sure there is no mechanical noise occurring acoustically that the pickup is sensing. Regarding his second suggestion, if there is oxidization in the FX return jack, it can make intermittent crackling noises, especially at low frequencies. I had this problem with my GK 400RB, and fixed it by spraying contact cleaner in the FX jacks.

Or could it be mechanical rattling? I had to re-do the foam insulation in my 200MB combo to prevent mechanical vibration of the chassis. Does the distortion still happen when engaging the low-cut filter on the amp?

[Keyser Soze]

Originally Posted by Birdbass

Hey everyone,

I've had my GK MB150E for 2 years, have never had a problem with it, love the sound. I use an underwood pickup (using only one transducer on the low end) and typically have everything on the amp set to noon, with the exception of the hi-mid, which I'll usually roll back to almost nothing. My bass sounds great - like an upright, only louder.

HOWEVER- recently I've noticed distortion on the E string. It's frustrating because everything else is fine- woody, balanced, cuts through...then the E with distortion. Anyone else having this problem? Suggestions? Thanks!

I bought an old GK MB200 off an esteemed TBer several years ago and immediately experienced the same thing. I thought, "Re-foam, recone, new gaskets?"

I tried severaal different input sources; e-bass, e-guitar, acoustic guitar w/ onboard (lo-z) electronics. Same result: No distortion, unlike w/ my carved Christopher and old Realist.

I came to the conclusion (since adding a Fishman Pro EQ Platinum preamp) that 12 o'clock-ish is the ceiling for the master volume before the cab/amp starts to fart.

I'd love to hear others' experience.

[brooklynbassed]

Originally Posted by winston

Or could it be mechanical rattling? I had to re-do the foam insulation in my 200MB combo to prevent mechanical vibration of the chassis. Does the distortion still happen when engaging the low-cut filter on the amp?

The sealed cabinet and speaker (proprietary GK designed Eminence), make these amps special in several ways.
Problems occur when any of the rubber seals (foam) or the speaker surround (rubberized) becomes compromised. Rattling, buzzing, and percieved distortion occurs (especially at lower frequencies, because the air is pushing its way out of wherever the breech has occurred).
I have replaced two speakers and seals in my old 200MB and 200MP with good results. If you find this to be the problem, you can order the speaker directly from GK and then replace it yourself. The only way to do this is to inspect the speaker for any wear or tearing aroung the speaker surround (the rubber that supports the paper cone). You can look at the speaker through the grill to see if there is any damage. Replacement requires you to take the entire cabinet apart, screw by screw, panel by panel. There are other threads in this forum about that. Good luck.

Everett Boyd

[fdeck]

Always worth checking your cord. I have gone mad searching for amp / pickup problems, just to find it was the dang cord.

[Birdbass]

Thanks for all the suggestions. I'll definitely be doing a serious 'quality check' of all my electrical/pickup/speaker connections.