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DIY Stompboxes => Building your own stompbox => Topic started by: Clubman35 on November 16, 2007, 05:13:19 PM

Title: radio station interference
Post by: Clubman35 on November 16, 2007, 05:13:19 PM
I'm picking up a radio station with my fuzz that I built. It's only when the volume on the guitar is at 0. I think I remember reading something about putting a cap on the input jack to ground.?.?.? Can't seem to find that thread....any ideas?

Many thanks...
Jim
Title: Re: radio station interference
Post by: yeeshkul on November 17, 2007, 03:18:16 AM
- check the grounding of the circuit
- try a large cap (220uF) between the battery lugs
- use shielded wire for input

is the fuzz in a metal box?
Title: Re: radio station interference
Post by: alfafalfa on November 17, 2007, 04:47:56 AM
Try a 68 K resistor from the input to the base of the first tranny , could do the trick.
Just like in a tube amp , it helped me with some fuzzes , distortions .

Alf
Title: Re: radio station interference
Post by: frokost on November 17, 2007, 05:55:27 AM
Put a small cap, like 47pF or something at the effect's input, that should take care of things. Don't put it between the input jack and ground - imagine what happens to the signal if you have several pedals with that cap in a chain. All those caps in parallell will surely suck a lot of treble out of your signal.

This topic has been covered a lot earlier, a search should give you a lot of information about this.
Title: Re: radio station interference
Post by: nooneknows on November 17, 2007, 06:40:52 AM
IMHO a 47pF is not a big cap, the treble loss is quite low, even with a low impedance input of a fuzz face and with multiple effects in chain (and a fuzz influences a lot the harmonic content of the signal), I think the effect of radio stations coming through the output is way worse... :) 
Marcello
Title: Re: radio station interference
Post by: frokost on November 17, 2007, 06:49:34 AM
I agree. My point was, however, that one should put the cap on the effect's input and not on the input jack so that it's only in the signal chain when the effect is on. It's a matter of good practice - if you put a 47 pF cap on the input jack of, say 6 pedals, the total effect of these in parallell will be 282 pF, and that you would notice. Assuming we're talking about a true bypass setup, the idea of having the cap on the input jack kind of takes the point of that away.

I don't know if this was what clubman meant, but I just thought I should point it out. Don't mess with the clean signal.