Fuzz Face builds keep popping

[canman]

Hey guys,

I built two different renditions of the Fuzz Face today...and both keep giving me this odd, random popping.  I'm not necessarily asking for debugging help because the circuits work...I just can't figure out why they are popping/thumping randomly.  Maybe my amp doesn't like them or something.  I dunno.  But it's bizarre to me that it would happen on both versions (Creepy Fingers FF and Eric Johnson sig FF).  

Has anyone else had this problem?  Even when I pull the transistors out I still get the weirdness...is this a bias issue?

Thanks for any suggestions.  I have the layouts I used below, but like I said, the circuits work, I just have this popping noise.  I'm just wondering what might cause that popping..?

[MaxPower]

Maybe a bad solder joint? A bad connection which causes the power to cut out intermittently can produce popping.

[canman]

I'll go over all the solder joints this afternoon, but I'm not sure if that's the cause...the "heartbeat" is pretty regular, on both circuits.  Very odd...

[GGBB]

How are you powering the pedals? When the transistors are pulled, the only paths to the output is from the power input and ground. Either the noise is coming from there, or you have some cap problems (discharging), or there is a solder problem (stray strand, bad joints, ...). You say "heartbeat" - does that mean it is continuous and not random?

[canman]

Yeah, it's continuous, but somewhat random.  It's a consistent popping, but not *exactly* the same interval.  I'm powering it with a 1 Spot power supply.  I'll investigate the caps later on too and see if I can find something.  What's weird is I have the same exact issue with two separate fuzz face boards...I'm just not meant to play fuzz faces haha!

[davent]

Can you try powering it/them with a 9v battery?  Does that change anything? If it does... some of these circuits really don't like power supplies no matter it's quality and you need to add some filtering at the power input,  a 100r in series followed by a 100uF cap to ground might do it.

[canman]

Interesting...I'm about to trace the circuit, so I'll hook up a 9v battery first and see what happens.  I'll let y'all know what I find!

[canman]

Well, it appears the power supply is the culprit.  Using a battery eliminated the popping, so it looks like I'll have to do some power filtering!  I'll try the 100R and 100uF additions and see if it works. 

What is the basic theory behind power filtering anyways?  I get why we need to do it, but I don't quite understand how the pieces all work together to actually filter the power.

[Arcane Analog]

Definitely the OneSpot. They are one of the worst powersupplys on the market - especially for germanium based pedals.

[anotherjim]

I think they're both Silicon FF's?
Anyway, the EJ looks like it does have a supply cap - the 47uF. That could be bigger, up to 470uF might fit (depends on what physical size caps you have. No room for a series resistor though, it will have to be in series with the 9v power wire.

+1 100R & 100uF should be enough.

The Creepy is worse since there's no existing cap and no place for one. Probably make a little "satellite" board for a cap and resistor that can go in series with the power wires and be protected in heatshrink or tape.

[canman]

OK, I used a 1.8K (I heard somewhere else that a 4.7k resistor simulates a 9v battery resistance, so I split the difference more or less) and a 100uf cap...works beautifully.  Really cool!  I may just have to build a power filter box to run my 1 Spot into and then send the 9v out to all my pedals...could explain the motorboating I've been hearing!  This is excellent news!!

[GGBB]

Normally 1.8k would be excessively high - typical is between 10 and 100 ohms - but I'm not sure it matters in fuzzes as long as you bias the transistors to where they need to be. 4.7k is probably a dying battery simulation - fresh batteries are nearly zero.

The theory is a low pass RC filtered formed by the resistor and the cap.  All you want is pure DC, so filtering out as much of the AC spectrum as possible is desirable - especially 50/60Hz mains hum and the 100/120Hz rectified double of it. The lower the frequency of the filter the better = bigger cap and more resistance. Since it is a first order filter - 6dB per octave - the farther away from the filter frequency the noise is, the lower its volume will be. But you don't want so much resistance that the circuit can't get enough voltage and/or current. Also, a small ceramic cap of about 10-100nF in parallel with the big cap is often recommended as it will have much lower effective resistance than a big electrolytic and will help get rid of EMI and RFI interference. The big cap also acts as a power reserve to smooth out the ripple of the rectified mains AC - the bigger the better.

[canman]

Interesting, and mostly over my head!  Some good stuff to research this evening for sure.  I'll swap out the 1.8k with a 100R resistor and see how it sounds...I need to do it to a few other pedals too, as the 1 Spot is apparently noisy with some circuits. 

Regardless, I'm just stoked that the power supply is the cause of the motorboat, and that my amp doesn't need aid...thanks everyone!