Whats this noise? (when bypassed, oscillates when controls are moved) Video Incl

[steveyraff]

Hey guys,

So I built about 4 pedals recently. 2 of them were these Fuzz pedals. I've build dozens of this exact pedal before, and never had this problem. However, with the last 2 I've built, they both have this exact same problem. It makes me believe its an issue with a part rather than an error on my behalf with wiring/soldering etc. The only thing I can think of is that they use a 2n1306 transistor. The previous dozen or so I made used the last batch of 2n1306's I had. These recent two with this weird noise are the first I've built using a new batch I just recently bought. Could it be them? What is most likely to cause such a problem? Its very irritating! I've been trying a jumper wire to experiment grounding things better but that doesn't seem to help at all.

VIDEO: (audio low when bypassed, you may have to listen carefully)

[GibsonGM]

I could see some sort of oscillation going on with the Qs, sure (I mean, that is what we're hearing)....AND it's coupling into your output wire, so long as your offboard wiring has been done correctly..that seems more of a problem.

I'd reassure myself that my switch wiring is good....and try using shielded wire for input/output, see if that helps...are you using a 'grounded input' switching scheme?  That might help, too.

[steveyraff]

I could see some sort of oscillation going on with the Qs, sure (I mean, that is what we're hearing)....AND it's coupling into your output wire, so long as your offboard wiring has been done correctly..that seems more of a problem.

I'd reassure myself that my switch wiring is good....and try using shielded wire for input/output, see if that helps...are you using a 'grounded input' switching scheme?  That might help, too.

I always use this one: (EDIT: But without the battery, and I ground join the input and output sleeves)

[steveyraff]

...also, its not as bad when I don't have the back panel on - but it is still there.

[EBK]

I'm with Mike on suggesting you change to a grounded-input bypass scheme. 

Any chance you could post some pics of the actual wiring?

[steveyraff]

I'm with Mike on suggesting you change to a grounded-input bypass scheme. 

Can you elaborate on what that is or if there are guides to show that? I just dont understand why the dozens of this exact pedal I've already built didn't have the same issue, but these two recent ones do. I haven't changed any methods of building etc.

I can get pics up tomorrow.

[EBK]

I suspect that your ground is isolated from your enclosure due to paint around the jacks or the like.  But, without seeing it, just a guess.

[bluebunny]

Can you elaborate on what that is or if there are guides to show that?

Check out the Tonepad wiring document.  Page 5 is what you're looking for (but without the battery snap).

[Kipper4]

[steveyraff]

I guess I just don't understand why these two are making the same noise, if I always wire all my pedals up the same way - why only the last two builds?

Anyways, heres a pic:

[GibsonGM]

There could be many reasons, stevey...all YOU have to do is satisfy about 2 conditions and you have oscillation.   Fuzzes aren't clean circuits AT ALL, so it's not uncommon for junk like this to go on.

I'd try the grounded input...but if you're curious, try changing in/out wires to a shielded type, grounded at one end.  Try moving some wires around with a pencil.   These Antennas may be involved in the feedback path.

Lead dress, length (in/out too long...), length of ground wire, missing ground connection (to the back?), orientation of caps to transistors, and more...all can play a factor.   

MAYBE your first 2 transistors had a gain of 1< oscillation point, and the rest are 1 above it! LOL 

[EBK]

Is the metal "can" electrically connected to one of the terminals in these transistors?

[EBK]

Did you buy this new batch of transistors from the same supplier as your last batch?

[steveyraff]

Did you buy this new batch of transistors from the same supplier as your last batch?

Nope, different. Thats why I am wondering is it those - its the only thing I've changed since this pedal and the previous and both are doing this. I've tried grounding it every which way and its not helping.

[steveyraff]

would a 2n447a trans be a suitable replacement for the 2n1306? Its the only other I have that seems similar.

[EBK]

Did you buy this new batch of transistors from the same supplier as your last batch?

Nope, different. Thats why I am wondering is it those - its the only thing I've changed since this pedal and the previous and both are doing this. I've tried grounding it every which way and its not helping.

"Every which way" should obviously include this, but I'll ask anyway.  Did you try with the circuit input grounded?
Also, does the oscillation go away when the effect is engaged?
Finally, does everything else seem to be fine with these pedals?

[steveyraff]

Did you buy this new batch of transistors from the same supplier as your last batch?

Nope, different. Thats why I am wondering is it those - its the only thing I've changed since this pedal and the previous and both are doing this. I've tried grounding it every which way and its not helping.

"Every which way" should obviously include this, but I'll ask anyway.  Did you try with the circuit input grounded?
Also, does the oscillation go away when the effect is engaged?
Finally, does everything else seem to be fine with these pedals?

I just don't understand 'input grounded'. I thought my input is grounded all along. There is grounding going from its sleeve to the other sleeve and to the footswitch, and the other sleeve is grounding everything else too. I even but another wire going from the input sleeve to the ground point of the circuit, and to the ground point of the power jack and its all still the same.

Yes, the pedal works fine in every other way. And no, there is no oscillation when the pedal is engaged.

I am so frustrated with this thing. I can't figure this out. 

[YellowBoy]

"Input Grounding scheme"

This is referring to the circuit input, not the input jack, being sent to ground while in bypass.  Your current wiring scheme (on the switch) leaves the circuit input "floating," so picking up any aul muck floating around the box and amplifying it just like it does to your guitar signal.  Change your wiring scheme to one that will ground your (circuit) input when in bypass like this...

http://tagboardeffects.blogspot.co.uk/2012/02/offboard-wiring.html

(sorry...need to have another wee read on embedding pics )

[EBK]

Actually, your switch wiring just needs one extra wire added....

From your original wiring diagram, add a wire from the top left (currently unused) terminal to the bottom row center terminal (shared with the circuit input).

[bluebunny]

It's what the Tonepad #5 wiring does: when you're bypassed, the input to your circuit is grounded.