Fuzz factory clone, now with radio station!

[chromesphere]

Hi all!

Built a 2nd madbean zombii fuzz (fuzz factory) with the light plate like my profile picture.  Only difference with this one is i used russian GT308v's instead of the set i bought from small bear (which i think were 2N....or PN...sorry cant remember specifically).  Pretty sure there is no other difference between the two.

First one i built 12 months ago approx, works fine, no problem.  The 2nd one (the new one with russian transistors) seems to be picking up, what sounds like, multiple radio stations at once.  It sounds like a party, a bunch of people talking all at the same time, some piano playing as well.  Seriously...Maybe i've inhaled too much flux vapour?

When the drive is 90% to full its audible.  Pretty sure it only does it when the stability is cranked up (ie most stable, no squeling etc).  Also seems to do it on specific settings of the gate and compression settings.

Anyone encountered this before?  Any particular area i should look at?  I was thinking the trannies might not have shielding, where as the first did.  These particular transistors seem to have the collector connectored to the case. The only other time i have encounter RF interference was my first build!

Cheers for any help!
Paul

[Seljer]

I'm pretty sure in the fuzz factory you'd call that a feature

In any case, the solution to this is usually to add some small capacitors either cut away or lower the gain for radio frequencies. Try around 47pF from the base to the emitter of the first transistor, or 100pF or so from base to ground.

[chromesphere]

Hey Seljer,

Thanks for the advice, i have connected a 100pf cap from q3 (the one i suspect thats producing the noise) to ground and it did indeed remove the radio interference.  However, the RF noise has been replaced with a, sort of static noise instead.  I dont think the cap addressed the issue, it just sort of changed the type of noise im receiving (still an improvement though!  Radio through a pedal is an instant fail isnt it? . 

I also did notice if i put my finger on both cases of the trannies, connecting them together, the noise is improved.  I cant imagine this is a good idea, but i did consider putting a short, like a wire link, from case to case?

Paul

[Ben N]

What language is the radio in?

[chromesphere]

What language is the radio in?

Satanic.

Im not sure. Sounds like there are 20 people talking at once.

[deadastronaut]

what a bonus..



shielded in/out?...

[Kesh]

Satanic.

You should hear a reverb pedal that picks up radio. Sounds like it's coming from the darkest void of hell.

[Processaurus]

Yeah, I've ended up listening to alien conspiracy stories on Coast to Coast a couple times on my fuzz factory. 

[chromesphere]

what a bonus..
shielded in/out?...

lol well, i'd leave the talking if they were speaking some evil language.  Unfortunately it sounds more like a posh wedding reception, so its GOT TO GO
No shielded in/out.  It could be contributing to the problem.  I'm still convinced theres something going on with the trannies.  I ran out of time last night.  My inferior human form requires an 8 hour rest period believe it or not. but i will check it out tonight after work.

You should hear a reverb pedal that picks up radio. Sounds like it's coming from the darkest void of hell.

I gotta get me one of those

Paul

[moosapotamus]

Radio through a pedal is an instant fail isnt it? . 

No way! Not if that's what you were going for!
I recall a number of posts over the years from people wanting to know how to do this on purpose!

Did you try filtering radio frequencies at the input? Like in RG's "what are all those parts for" article?

~ Charlie

[chromesphere]

A resistor straight after the RPD?  Thats easy enough.  Is there a "typical value" that is used or is it circuit dependant?
Paul

[puretube]

it`s "His Master`s Voice"...

[stallik]

Had this effect on a dr boogie. Went round in loops before finding that ground between input & output was faulty ( my end pin jacks did not earth to the chassis). Running a direct wire sorted the problem but I sometimes think about putting a switch in there just to listen in to Russian radio

[chromesphere]

Had this effect on a dr boogie. Went round in loops before finding that ground between input & output was faulty ( my end pin jacks did not earth to the chassis). Running a direct wire sorted the problem but I sometimes think about putting a switch in there just to listen in to Russian radio

Thats interesting, i made one of the jacks a bit tight and had to bore it out a couple of mm to fit it.  Maybe its not making a proper connection!  I'll check that when i get home, thanks!
Paul

[EATyourGuitar]

I built a fuzz factory with the in and out cables to the footswitch shielded. a proper AC128 was used. I did not ever experience any radio noise. consider this the control group.

on topic of building circuits that pickup radio on purpose, I think you would like this ----> http://www.techlib.com/electronics/allband.htm

[chromesphere]

My previous build didnt use sheilded wire or ac128's and it worked.  Can we use that as a control group too?

Seriously though thanks for the reply, if all else fails i have some ac125's, ill chuck them in and see what happens.

Paul

[chromesphere]

I examined the output audio of the pedal a bit closer when i got home from work.  It appears the 100pf cap from q3 base to ground didnt fix the issue.  The radio pickup was just moved to a different place.  So i soldered the 2nd 100pf cap from q2 base to ground.  Still radio coming through.

So i was messing around inside it trying to determine if there was a lose component, or a specific wire that was causing the issues, when the output signal went completely...then i cried a little.

At this point, i've got nothing to lose so pulled out the pcb desoldered the GT308V's and put in ac125's.  It works again, and guess what?  No RF!?  I think i orginally suspected the GT308v's werent shielding RF or were just no good for the circuit.  Hopefully thats proven now.  I'm going to neaten it up again and call it a day, assuming all is good again

Thanks for the replies / help!

Paul

[RandomGlitch]

This is funny thread, Paul!

Was playing with my band the other day, our guitarist was using the fuzz factory I'd made (using transistors you supplied me!) and sure enough, radio was coming through his amp.  It actually adds a bit to our songs, many of them being about radios and television and stuff.

We actually said at the time "it's possessed!" 

So yeah, for us, it's a feature. (Not that we're devil-worshippers or anything haha)

[chromesphere]

Wow!  Your having the same issues?  Id read a few times about the shielding issues with ge's but id never seen it before!  Which trannies did i send to you?  Were they the IT308V's (GT308v's?). Sorry about that random glitch

Paul

[RandomGlitch]

Oh no  - please don't think it was meant as a criticism or complaint in any way! 

I'm pretty sure that the Fuzz Factory can be set in some pretty extreme ways, with lots of gain - in many ways it's inevitable, and I think that plugged into a Fender Strat in a dodgy rehearsal studio is all a big radio antenna!

I had not experienced radio interference before that at home (quiet suburbs), so I guess it depends on where you are (rehearsal studio near highway/industrial area etc).

Anyway I used the "top hat type 80's" (I think) trannies, whatever they are.