Can't Stop Humming

Hi,

I can't help thinking that you may have a fault in the first or second stages of the amp. What does the guitar actually sound like when playing through it? Is it extremely distorted? or clean if only the hum wasn't there? I have one of those little Fender Frontman 15w amps that was very noisy but was due to one of the input stages shorted inside the first dual op amp. It's relatively easy to blow the first stage of preamplification by overdriving it with a guitar effects unit/pedals etc.

Richard

Probably still some of the original black rubber and cotton insulation wiring there I suppose. The rubber goes hard and brittle and breaks away from the conductor thus exposing the wiring to possible shorts and other hazards. Maybe the rats have also had a good feed on the insulation....

It is rather difficult for anyone to give a definitive answer to your problem on this forum, without having heard the symptoms. We can only go on similar symptoms experienced by some of us and make suggestions as to possible causes.

Good luck....

Hi, Richard;

I didn't even have time to blow it, rather, the hum was there from the first moment I plugged the guitar into the amplifier. The sound from the guitar is clean except for the hum, but as I found out, the hum is only present when the guitar cable is plugged in suggesting that the [cheeap] cable is most likely to be at fault.

Ron

Plug the cable into the amp and instead of plugging the other end into the guitar - short the tip to the body & see if the hum stops.

Hmm, actually that makes the hum worse.

Ron

The amp's faulty in that case.

Graham

It's hard to see in what way the amp could actually be faulty, though, given that Ron said that the guitar is perfectly clean and correctly amplified. If the cable is poor quality, with a less than adequate shield, shorting inner to shield at the remote end, could be just turning it into a long single turn hum pickup loop, particularly if the environment is electrically noisy or there are any power earth integrity issues.I would still feel inclined to try another better quality cable, or take the whole shebang across town to your sister's house, or wherever, and try it there.

One slight possibility comes to mind. Does the amp seem very very sensitive ? That is, does it sound like you've got sort of full chat, with the gain control up at only say number 2 ? The reason I ask this, is that I did once have a ProSound combo that suffered intermittently from hum, and it eventually turned out to be due to a feedback resistor in the first opamp stage, that ws going intermittently open circuit, increasing the gain of the stage so much when it did, that it picked up huge amounts of hum.

Arfa

Hi, Arfa;

No, except for the hum when the cable is plugged in, the amplifier behaves nicely and normally at all settings.

Ron

Then it's a cable or operating environment issue, not a fault. Like I said, try relocating it to another house temporarily, and see how it behaves.

Arfa

I went into my office, the only part of the house with all new wiring and virtually no 60 Hz noise, and tried the guitar and amplifer. As before, no hiss or hum untilt the guitar cable is plugged in. This pretty much cinches it for the prblem being in the cable.

Ron

Agreed

Arfa

Yes, way too many variables. Especially for a guitar/cord/amp combo that cost a total of $100.

Did you try...

I don't remember if you mentioned, where did you buy this set? Online, or through a catalog? I would take all this stuff down to a good music store ( a MUSIC store i.e. musical instrument sales, not a record store). Any reputable shop will be happy to help you isolate the problem, maybe even offer suggestions to correect. Of course, depending on the salesman, the correction could be rather pricey :)

I got the combo from Amazon.com, and now I have only one guitar (well... except for my old Casio DC-10 digital geetar, but that's a horse of a different color) and *one* amplifier so I have to rely upon the evidence at hand which points to a cable problem. I've ordered a new shielded cable, and in about a week or so, I'll know for a fact whether it's a cable problem or not. What was it Sherlock Holmes used to say? Eliminate the impossible and no matter how improbable, what remains has got to be the answer? Something like that... Anyway, going to a music store is a last resort for me as I have way too many other things to worry about these days. But nine will get you ten the problem is in the current cable. :-)

Ron

Or the screen is open on the cable.

Ron(UK)

Or the ground side of the input socket is open circuit, probably fractured solder joint. It will ground when no plug is inserted if it has a shorting contact on both sides.

Ron(UK)

But he has said that it all works ok with the lead and guitar plugged in - guitar sound is normal, amplification level is normal, just rather too much hum. Thus, there cannot be an open circuit either on the cable shield, or on the ground PCB terminal of the input jack ...

Arfa

Yes, might be the cable. What sort of pickups does the guitar have? Single coil? Humbuckers? Single coil pickups can be very, umm, hummy.

That is very true. Usually, if the problem is due to pickup in the pickup ( if you see what I mean !! ) it is substantially affected by touching the strings or the surface of the pickup. A decent cable can make all the difference with a single coil pickup.

Arfa

As it happens, I just had a Roland combo come in for repair with the same problem, humming regardless of whatever was plugged in. It turned out to be the shorting contacts on the second input socket (overdrive) tarnished. Of course guitar boy always plugs into the first socket leaving the overdrive socket open to the elements.

Ron (UK)