Odd sounds coming from amp

[ambissonnett]

I currently have a GK Backline 600 head and a GK 4x10 cab. Anytime I turn the volume knob or boost knob I get this scratchy, in and out sound from the amp. Also if I hit a note, I get a muddy, in and out sound again. It only returns back to a normal sound after a long, constant turning of the knob to get a normal clean bass sound. I also noticed when my head temperature gets really hot with the fan going, I don't have this problem.

Any ideas on what this is? Is it a simple fix, or something I gotta send out? Any input is appreciated.

[Rick Auricchio]

First and easiest is to try cleaning the effects send/return jacks.

1. If you have some contact cleaner, spritz a little on a 1/4" plug. Any guitar cable will do. If you don't have contact cleaner, a dry plug is OK. Do not spray cleaner into any jacks.

2. With the amp off, plug that in and out of the effects send and return jacks several times.

3. Remove that cable from the effects jacks and test the amp.

[Downunderwonder]

Sounds like dirty pots. B-String can tell you what's involved in getting to them on that amp.

Meantime it won't hurt to clean your send/return jacks as suggested, GK are famous for that.

[B-string]

I agree with dirty pots, all jacks should be cleaned. The effects return jack is a weak point with ANY amp that has a serial effects loop (more so if that jack is never used). The procedure has been covered many times and I could repeat for you, but any used amp should see a tech for a basic inspection and general maintenance (usually a small fee for the piece of mind). General maintenance SHOULD include clean and properly protect (special lube) all pots and jacks and any interconnect cables.

[BogeyBass]

wait that is kinda weird though.

the problem goes away if the amp is hot and the fan is on?

or did i read that wrong.

[ambissonnett]

No you didn't, I noticed this last summer. I was rehearsing outside with my old band last summer and it had to be in the upper 80s on a sunny day. I remember wanting to turn it up and it didn't give me a problem. It happened on multiple occasions, and sometime occurs if I've just been playing for awhile in a warmer environment.

Thanks for the help! I try and get to that this week. By the way, any idea where I can get some contact cleaner? And could I use my chord I use to practice to do this? Or should I get one that I don't use?

[JimmyM]

Contact cleaner should be available in any Radio Shack. But get one designed for pots as some of the contact cleaners can take out the lubrication in the pots and ruin them. Deoxit is the standard, but I think RS has a house brand that's safe for pots.

[two fingers]

And this goes without saying but............

Make sure the amp is both turned off and unplugged before spraying any liquid anywhere near your amp. You probably already knew that but just making sure.

[B-string]

The house brand from Radio Shack sucks though! DeoxIT or RidOx is much better.

NO WD-40 !

[bedroommuso]

I actually read the thread title as "Old sounds coming from amp", and I thought, well, the answer is pretty self-evident isn't it? Must be an old amp.

Sorry. back on topic.