Can't get rid of Bypass Pop, I tried everything!!

[Sweetalk]

Hi!, i'm building an small stone with the tonepad pcb. Works fine, a little of lfo ticking but the effect works OK. The problem is that I can't get rid of the tipical true bypass pop, not even with the pull down resistors (on the input and/or the output)... I'm using a DPDT switch (I change 2 of them just in case) and millenium 1 plus, when I connect the mill board the pop it's even BIGGER... I doesn't know what else to do...

Thanks in advance!

[R.G.]

Mother Nature is whispering in your ear that there's a problem in either your circuit or your wiring.

Take your ohmmeter and measure the DC voltage on your input and output jacks in both bypass and effect switch settings. It should be 0mV all the time. If it's more than that, there is a range of values that get more and more hearable. Somewhere around 10-20mV it gets just hearable, and it's worse from there on out. So go measure.

I'm guessing that this is something you didn't try, right?

[Sweetalk]

Thanks RG for the quick answer... I thought about doing that but finally I didn't....

So, I measured.... on bypass I have 0mV on the input and output, on effect I have 0mV on the output and oscillating between 4 and 24 mV on the input, at LFO rate... What can be causing this and how can I fix it?, wiring problem?

[R.G.]

Ouch. Yep, that'll make it pop.

I'd look for the polarity of the input and output caps, and then at solder shorts, etc. I would think a solder short would be worse though. Caps first.

[Sweetalk]

The Small Stone has a 100K resistor in series with the output and then a 0.0068uF capacitor in series with that resistor, on the output has a 0.1uF cap and a 470K from output to grond, no polarized caps there to look. All the other polarized caps of the circuit are well oriented. Would a electrolitic cap on the input (in front of the 100K resistor) block that DC voltage?

[R.G.]

With those big resistors, check with your ohmmeter to see if the input and/or output caps are maybe shorted (resistance < 1K).

[Sweetalk]

They're not shoted... resistance is > than 500K, they should block the DC don't they?

[R.G.]

They should - but if they don't, then it's getting in some other way.

Are all your grounds connected properly? Are there any nearby traces on the board that could have solder threads?

[Sweetalk]

I've checked the wiring, re do some, cleaned the board, fluxed, resolder some things,  no more DC voltage at the input and/or output... but still popping. I putted a 1M resistor on the input of the FX board. Now I'm with no LED connected... the noise it's bigger with the color switch in the deepest position (tells me that the problem it's at the input as the noise it's affected by the phaser). Any more ideas??

Thanks for all!

[R.G.]

Hmm. I'll have to think about that one. I'll be back.

[shredgd]

Are all your grounds connected properly?

True, once I had the same problem, then I realized my ground path was an open circuit because of a solder break.

Giulio

[Sweetalk]

All the grounds are connected properly...still popping...

[amz-fx]

There is a 47uf capacitor that is located off the board in the Tonepad layout. Did you add this capacitor (Cb)?

If not, then you should put it in, but I would increase it to 100uf.

regards, Jack

[Sweetalk]

There is a 47uf capacitor that is located off the board in the Tonepad layout. Did you add this capacitor (Cb)?

If not, then you should put it in, but I would increase it to 100uf.

regards, Jack

Cb it's on the board on tonepad layout, Ca isn't. Both are connected (for Ca I have to put 0.22uF insted 0.1uF to get no LFO ticking), first I have 47uF for Cb, I changed to 100uF and nothing, still the same popping noise.

When I had the LED connected (with millenium 1 plus circuit) I tried the led pop noise reductor from amz lab notebook but it didn't work. I putted between the FET and the LED, i was wondering if putting it between +V and the FET will be more useful. But no the circuit is without  LED.

Thanks for all the help, some more ideas?

[amz-fx]

Hmmm...  I've heard it said that some footswitches have a mechanical "pop" that may be caused by contact bounce or some similar phenomenon. If this is the case, no changes in parts or wiring will fix the problem.

I do believe that a footswitch pcb will often add some rigidity to the 3PDT and help with this type of mechanical problem. It might be worth a try. Someone on this forum was making the pcbs.

regards, Jack

[Sweetalk]

Can be mechanical pop, the strange thing here it's that I been using this footswitches in several projects and no noise. In this one is HUGE, unfortunably the aren't for pcb mounting..

[petemoore]

  I don't like to say switch, but anything electro-mechanical is always worth a 'suspect mention'.

[R.G.]

I'm down to a few possibilities, based on your statements about what's been checked to be correct.

One is the mechanical switch switch popping thing. For that, try another switch.
Another is that bypassing is somehow causing the internals of the circuit to move around. This is actually one form of a wiring problem.
Another is that something about the layout itself has issues that result in the pop. Ground conductor routing can do this in some instances, but it's generally not a big pop.

So can you describe the nature of the pop? For instance, is it a tick, a pop, or a thump? How loud is it compared to your guitar's signal? Does loudness of the pop vary with controls?

And have you removed the Millenium 1 entirely? Or just the LED?

[Sweetalk]

We're talking about a Small Stone Phaser, one knob. The noise it's a big pop, loud, annoying, with this pop the pedal it's almost unusable for "live" or "studio", just home use, if you doesn't have troubles hearing that noise.

The sound of the pop changes with the modulation of the phase, setting the lfo for a low speed and switching fast enough the pop changes from treeble to bass with the modulation.

The Millenium 1 Plus it's only connected to the control lug of the switch, +V, GND or the LED are not connnected.

It's the 3rd NEW UNUSED switch that I try, all the same kind (X-Wing DPDT). I changed to an old 3PDT that I have lying around but the pop it's the same.

The wiring it's really neat and well-soldered, i'll double check again

[PerroGrande]

Can you post a diagram (or a link to a diagram) of your switching circuit?  In other words, are you switching both ground and signal, or are you leaving ground "common" and only switching signal?

Another question -- does the pop change depending on what is plugged in before the pedal and/or after the pedal?  In other words, does the pop change/vanish if you change the pedal/instrument that comes before/after it?

Does it pop with both battery and adapter power sources?