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DIY Stompboxes => Building your own stompbox => Topic started by: screamer on November 25, 2003, 10:52:06 PM

Title: Hum Hum Hum
Post by: screamer on November 25, 2003, 10:52:06 PM
Hi everybody,

I have big problem with hum generated by my pedals.(Wires are top quality.)
First box is a booster, second one is distortion.
When only one is on no hum,pretty silent but if the two boxes are on in same time,i have a lot of hum even when guitar volume is off ( i suppose that should be no signal from guit? :x
Any idea?

Thanks

Yves
Title: Hum Hum Hum
Post by: idlefaction on November 26, 2003, 12:45:50 AM
can you tell if it is 50/60Hz hum or 100/120Hz?  50/60 is usually caused by ground loops and 100/120 is often power supply related.

if you're using a power supply, think about these:
1.  are the supplies to various pedals isolated (ie from different transformers)?  if you're using a daisy chain type power supply, you may have enough hum creeping in from the ground loop to be amplified by the distortion/booster.  you can fix this by cutting ground wires, ensuring there is only one path from each pedal to ground (ie through the interconnecting cables or through the power supply cable.)  you can also fix it by having seperate transformers for each pedal.
2.  are you pulling too much current for your regulators?  if the strain on your transformer is too much and the output voltage drops enough before the regulator, large amounts of 100/120Hz hum can be present on your power supply line which will make their way into your signal.

if you're not using a power supply, can you turn it up and down with any of the volume knobs?  that will help track down the problem...
Title: Hum
Post by: screamer on November 26, 2003, 05:42:28 PM
Hi Idlefaction

First i'm using 9 volts battery, second when i crank volume pot of distortion even when the guitar volume is off the hum or hiss is increasing :x
Some bad signal in distortion?

Thanks again