I get a buzz noise from my Fender amp. If I turn the volume all the way up om my guitar it stops buzzing.

closed as unclear what you're asking by Carl Witthoft, Dom Mar 21 '17 at 13:23

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    No idea where the 'unclear' close votes are coming from... I've experienced this too: volume below max on guitar, you get hum; volume set at max, no hum. – topo morto Mar 15 '17 at 0:22
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    @topomorto it's unclear for several reasons. He didn't identify his guitar, nor did he test his guitar with a different amp, or a different guitar with this amp. We don't even know if this is a passive or active pickup guitar. – Carl Witthoft Mar 15 '17 at 11:23
  • @CarlWitthoft My assumption is that there would be a very limited number of reasons - perhaps even only one - why a guitar would be likely to hum, but stop humming when turned up fully. If that is not true, then yes, more information might be helpful - though a comment asking for the relevant information would have been much more friendly than commentless close votes. – topo morto Mar 15 '17 at 16:51
  • Is the buzz generated by (coming out of) the speaker or from the amp itself (the electronics)? – Yorik Mar 15 '17 at 18:53
  • Also: does the hum go away when the volume is zero? is the hum a maximum around 5 or around 8? – Yorik Mar 15 '17 at 19:21

I asked for a few clarifications, but I am going to go ahead and give some information about what I think the OP is asking about.

So the volume control is a potentiometer which is basically a variable resistor, which adjusts impedance to divide (reduce) the voltage.

When the volume is at zero, the output impedance is zero, and when the control is at 10, the impedance is basically the pickup impedance.

But when you turn the knob, impedance will rise appreciably to a maximum and then fall off again. On a normal pot, maximum will be at about 5, but on an "audio taper pot" it will be at about 8.

One can check the impedance of the circuit by connecting a multi-meter to the guitar cable (convenient) or the jack itself (less convenient) and then actuating the pot. That maximum measured impedance with a 250K volume pot is probably going to be in the neighborhood of 60-65 Kohms, but with a 1meg pot, it could be 250 Kohms.

Basically, higher impedance passes higher frequencies and this means a guitar with a 1Meg pot is "more sensitive" to hiss. So the OP probably has a high-value volume pot, which causes it to be more sensitive to noise, since it does not attenuate high frequencies as much as e.g. 250K pot.

Some of this unattenuated noise might be cold or loose solder joints, grounding issues, and even a mis-wired cable jack (check this if the noise is attenuated by touching the strings).

(Resistors do create their own noise (thermal noise) that is proportional to resistance value. It is unclear to me if this is a consideration in a guitar.)

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    Thermal noise is negligible in this application. – Doktor Mayhem Mar 16 '17 at 22:51

It's worth re-soldering all joints (if you're competent to do this). Maybe replace the volume pot. Note that with volume fully up, the volume pot and any interference it is 'picking up' is effectively shorted out.

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