Gallien Krueger 700RBii Buzz

[envy1400]

Disclaimer: I did a search for this but didn't see anything terribly specific to my problem but if there is a thread I should read please let me know!

I've had my GK 700RBii for a while now and its always had a buzz. Sometimes it's worse than others times. I've had a hard time detecting a pattern of when it is buzzing the most. At venues the amp is turned up loud and the buzz is very noticable. I have to run my DI through my sansamp because the buzz from the GK is so bad even when the ground is lifted. It buzzes without DI plugged in so I don't think lifting would help too much anyways.

I've been doing some expiriminting and noticed its worst with my T40 and Squire Jazz VM (both passive) and less buzzy with my Cirrus (active). I think it must be a grounding issue in the amp.

Here is a short video of the amp buzz getting worse as my bass is moved closer to the amp. The bass is plugged directly into the amp and no pedals are powered or in the signal chain.



TL;DR: GK 700RBii is buzzing and I think its a grounding issue. Any suggestions or thoughts would be a huge help! Thanks!!

 

[Mike A]

I've been doing some expiriminting and noticed its worst with my T40 and Squire Jazz VM (both passive) and less buzzy with my Cirrus (active). I think it must be a grounding issue in the amp.

Sound like a grounding issue, alright, but with the basses, their pickups and shielding/lack of shielding... maybe not the amp itself.

Does it buzz without a cord plugged into the input?

 

[envy1400]

It does not buzz with no instrument plugged in. Could the grounding on the input jack be screwy?

 

[Dave W]

It's your bass. The J bass you're showing in the video has single coil pickups in it. That's why when you plug the Cirrus in it's not nearly as noticeable.

With that said, it's not loud at all and it's not something I would worry about. If it really bothers you have your bass shielded and it may help.

 

[envy1400]

I completely forgot to account for single coil buzz. This may be what it is but even so it seems so very loud. Is it normal for single coil buzz to be really loud?

 

[Mike A]

It does not buzz with no instrument plugged in. Could the grounding on the input jack be screwy?

Possibly, or the input jack could be dirty... cord could be badly soldered, of questionable quality, etc.

 

[envy1400]

Small update. I just went to test out a different bass on the amp. Turned it on without the instrument plugged in (tuning mute on). Started out with a LOUD buzz for a few seconds then a large crackle and the buzz got a little quieter and then totally faded out.

 

[B-string]

What other electronic devices are near the amp? Like what is that white cord in the outlet going to? That power cord looks too small to be the original for the amp head, bad power cord can cause this.

 

[envy1400]

That white cord is a window AC unit. I went ahead and unplugged it and I am still able to replicate the buzz. It maybe the case that the power cord is not the original one. I bought this amp used several years ago.

After the buzz fades out I am able to turn the amp off and then on after a few seconds and even a couple minutes and there is now buzz. However, if I leave the amp off for 5 or more minutes when I turn the amp on the buzz is present. Again to determine this I had no instrument plugged in. One of the times I was able to reproduce the buzz I plugged in my Cirrus (no pedals in the chain) and the buzz was still present. This buzz is not single coil buzz ( although the buzz in the video above was probably single coil).

I wrote the above and just did another test. I'll post the video from this one in a few minutes. Starting to believe its the power cord. If I tug the power cable up the buzz completely goes away. I'll upload the video soon. Thanks so much for your help guys.

 

[David Jayne]

The ground in the power cable isn't 'making' reliably. Try a different cord.

 

[BrentSimons]

Small update. I just went to test out a different bass on the amp. Turned it on without the instrument plugged in (tuning mute on). Started out with a LOUD buzz for a few seconds then a large crackle and the buzz got a little quieter and then totally faded out.

Hi there my friend,
My GK 400RBIV does the exact thing. I had to send it back to GK for servicing. I tried a local repair shop that is a GK dealer and they Deoxit (ed) but the same issue remains. Hope this helps,
Brent

 

[envy1400]

Thanks for the help guys I think I may have fixed the problem. I went ahead and ran by GC and picked up a new power cable. The amp is much quieter now. There is some buzz when the woofer is cranked but I'm assuming this is normal. If it fails to have fixed the problem with venues I'll be back. Thanks for the suggestions guys!!

 

[BassmanPaul]

Good Grief!! It's perfectly normal. All amps with a power transformer will do this. The hum is induced into the bass's pickups where it's amplified by the amp. Even hum buckers will exhibit this behaviour. The cure is not to stand too close to your amplifier. Simple as that!!

 

[envy1400]

You're right the buzz in the video was normal. There was a much louder problematic buzz that didn't appear in that video. The louder buzz and crackle was what I was trying to diagnose. I was confused when I posted that first video!