Amp hum

Sleeping Martyr

Sleeping Martyr

New member
Hey guys, so I have a mildly annoying hum coming through my amp (Mesa .50 caliber+ and meas 4x12 cab) Its worse depending on the guitar (strat is worst obviously) but its always there and maybe I hadn't noticed before but I don't think it always was there. I've tried taking everything else out of the chain so its just guitar cable amp and its still there so its not pedals or anything. I play fairly high gain and loud but not insane levels. I've also tried the ebtech humx noise eliminator and it didn't do anything and in fact seemed to make it a bit worse.

My question is, any other ideas?? how much of a difference would high end patch cords make and what if any difference would a high end speaker cable going from my amp to cabinet make?? Right now I'm just using generic yorkville cables, not bargain bin quality but not high end either, any ideas??


Mike
 
Re: Amp hum

Have you plugged the power supply into a power-conditioner or other such device? The noise may not be so much your instrument or chain, but noise coming from your outlets.
 
Re: Amp hum

I tried the ebtech Humx and power bars etc but it didn't seem to do it. And its in various locations not just the same place, thats what makes em think its something else. Thanks dude!
 
Re: Amp hum

I'd try swapping your pre amp tubes next... even just swapping them around if you don't have any spares.
 
Re: Amp hum

Cranked guitar amps are noisy, period. You're right, they're worse when you use a single coil instrument, but they are what they are, an unbalanced signal going into an unbalanced amplification system.
 
Re: Amp hum

It could just be some corrosion on a tube socket. Take out each tube and clean the sockets really well.
 
Re: Amp hum

1. Check your cable. Try a different one.
2. Did you try a different guitar? Maybe a ground connection inside your guitar has come loose.

Then check this link for more tips... http://www.geofex.com/ampdbug/hiss.htm


noisy tubes

Noisy plate resistors. The carbon composition resistors used on the plates of preamp tubes often go very noisy, especially in older Fenders. If swapping tubes does not fix the trouble, locate the circuit that seems noisiest by tube swapping, and then replace the plate resistors in that circuit with equal-value metal film or metal oxide resistors. You can use carbon comp if you can find them, but the problem is likely to recur.

Noisy resistors in the B+ decoupling string, often around 10K in value

Unusual: An ultrasonic oscillation can cause an intense insect-like hissing that sounds very much unlike normal hiss.

Rare: leaky coupling capacitors or faulty controls

Rare: a slight ongoing arc on the output tube socket(s)

Rare: a bad solder joint somewhere in the signal chain

Rare: internal arcing or noise in almost any part in the preamp section


A good way to divide and conquer is to turn the volume control(s). If the hiss changes levels as you do this, then the source of the hiss is something that affects the stages of the amp before the volume control. A faulty, hissing preamp tube will be turned up this way very quickly. Conversely, if the volume control does not affect the hiss, the cause is somewhere after the volume control. In general, the volume level of the hiss is an indicator of where the hiss is occuring - the louder the hiss, the more likely its source is near the input of the amp where the gain applied to it will be the greatest

The procedure of locating by removing one tube at at time working from the phase inverter/driver back towards the input until removing a tube no longer stops the hiss should then localize the problem to one tube's worth of circuitry.


 
Re: Amp hum

Thanks so much guys so:

-I tried switching around the pre amp tubes, didn't seem to make much of a difference
-The Hum is there when not plugged in though not as bad
-Its in both channels but worse in the distorted channel
-Tried a few cables (albeit nothing high end) and it was the same
-still worse depending on the guitar its in

Any ideas?? Should I just take it in to get looked at??
 
Re: Amp hum

don't get it looked at just yet, im drawing a blank but im sure someone on this forum will be able to at least help you identify the problem.

check what colour the tubes glow.
 
Re: Amp hum

The tubes in the amp are only about 6-7 months old. And the amp seems to still do it even when not cranked. We played some weddings this summer where it wasn't turned up super loud but it still had that hum
 
Re: Amp hum

Sleeping Martyr said:
The tubes in the amp are only about 6-7 months old. And the amp seems to still do it even when not cranked. We played some weddings this summer where it wasn't turned up super loud but it still had that hum
Click to expand...

get a full set of tubes (you can keep the old ones as spares anyway). See how you go after that. No need to call an electrician until you change the lightglobe.
Tubes can go south in a lot shorter time than 6 months. If that doesnt fix it, then its time to call the tech.
 
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Re: Amp hum

long time ago, I had an amp in the basement of the company where I work with. The hum was very loud. I tried everything, shielding, actives pickups, tubes, etc. I thought it was common of tube amps. One day I took the amp to the 6th floor for some laboratory test, and I discovered the beauty of an amp with no hum. It was the bloody room that did the amp hum.
 
Re: Amp hum

crguti said:
long time ago, I had an amp in the basement of the company where I work with. The hum was very loud. I tried everything, shielding, actives pickups, tubes, etc. I thought it was common of tube amps. One day I took the amp to the 6th floor for some laboratory test, and I discovered the beauty of an amp with no hum. It was the bloody room that did the amp hum.
Click to expand...

Yup, i used to build amps in a room that turned out to have no ground connections on the power outlets. I bought a power-point tester for about $10 and check any room where i plug my gear in ever since then. Best ten dollars i ever spent.
 
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