Relay Bypass Pop At First Engage

[mickeybellinello]

Hi to All!

I recently built a custom crybaby pedal.
Because I always hated the standard on/off activation I buyed a relay true bypass module from stompville site that let me to mimic the switchless activation. I drill a hole in the top plate ad added a spdt momentary switch that activate the way only when it is pressed. So the wah is active only when the switch Is pressed down.
All works except the tedious fact that at the first activation it makes a pop. The following times it's pretty quiet.
What can cause that?
The user reference are here:
https://www.stompville.co.uk/shop/index.php?controller=attachment&id_attachment=19
the page of the site is:
http://www.stompville.co.uk/shop/28-true-bypass-bare-pcb.html
Any ideas?
Thanks

[cloudscapes]

How have you arranged your pulldown resistors on your effect input/output?

[mickeybellinello]

How have you arranged your pulldown resistors on your effect input/output?

I used this schematic:



UPDATE: In my pedal the input buffer is missing so the FX in cable goes directly to the 68k resistor.

do I need more?

Thanks

[cloudscapes]

So you don't really need a pulldown on the output since VR1 kind of acts like one. There's none on the input, but the cap is so small that I'd be surprised if that was a huge issue. I would start by making sure all the parts that need to be grounded actually are. Especially on VR1. And maybe try adding a 1m resistor between gnd and the crybaby input just in case. Doesn't matter if it's messy, it can be just as a temporary test.

Could be the quality of the relay too, not sure. I use those panasonics and haven't had issues with them yet.

[mickeybellinello]

So you don't really need a pulldown on the output since VR1 kind of acts like one. There's none on the input, but the cap is so small that I'd be surprised if that was a huge issue. I would start by making sure all the parts that need to be grounded actually are. Especially on VR1. And maybe try adding a 1m resistor between gnd and the crybaby input just in case. Doesn't matter if it's messy, it can be just as a temporary test.

Could be the quality of the relay too, not sure. I use those panasonics and haven't had issues with them yet.

here I am, thanks for support! The VR1 is the Crybaby pot ( I use a 250k here and it's grounded).
the cin1 has been replaced with a 100nf one.

Tried the 1M resistor... no luck!

[mickeybellinello]

I forgot... in the output of the wah circuit I added this:

[mickeybellinello]

Sorry for the third post. I tried to exclude the output buffer/boost and no pop at all.
What can I Do to solve?

[GibsonGM]

Is there an output cap?  Pin 6 is output - I don't see one.  Maybe this is some Vero trick? (don't like Vero much).    If there is no output cap - there is your pop...

I wish every Vero came with the real schematic.  Not having it is like trying to plan a road trip with a satellite pic instead of a map...

[mickeybellinello]

Is there an output cap?  Pin 6 is output - I don't see one.  Maybe this is some Vero trick? (don't like Vero much).    If there is no output cap - there is your pop...

I wish every Vero came with the real schematic.  Not having it is like trying to plan a road trip with a satellite pic instead of a map...

Hi!
Watching it I see that the C2 Is connected to the ic output. The signal than goes to r4 (one lug connected to ground) to r3 to output

The strange thing is that it pop only at the first press. the other switching are all dead quiet.
I mean. I connect the pedal to psu. the first time I press the switch there is a bump, the second/third times etc all is fine...

[mickeybellinello]

Last update... I completely removed the buffer circuit.
Again...pop at first on.

[Groovenut]

generally IME, pop on first switch and not others is a cap that is either charging or discharging very slowly and there is transitioning DC on the first switch. How soon after power up are you trying the first switch?

[mickeybellinello]

generally IME, pop on first switch and not others is a cap that is either charging or discharging very slowly and there is transitioning DC on the first switch. How soon after power up are you trying the first switch?

Thanks so.
I tried immediately and After some minute. At first stomp got pop

Another thing. I haven't got the input buffer, signal goes directly to R1

[Rob Strand]

do I need more?

What cloudscapes is saying is you need a 2M2 in the *input* side of Cin.  Without that you will get pops for sure.

[mickeybellinello]

do I need more?

What cloudscapes is saying is you need a 2M2 in the *input* side of Cin.  Without that you will get pops for sure.

Hi!

Added the resistor but same situation unfortunely...

[Rob Strand]

Hi!

Added the resistor but same situation unfortunely...

Hmmm, that's weird.  Especially since you have removed the buffer board.

As you found above, the buffer board has an output cap and a resistor to ground.   It has an input cap and uses the volume pot as the input resistor to ground.   So the buffer board looks OK.

OK, as an experiment, what if you connect a wire from the input jack directly to the input at Cin, leave all other wiring in place.    This isn't a solution but it might help narrow down the problem to the input or the output.

[antonis]

Why I never trust relays (latching or not) without diode across them..?? 

[mickeybellinello]

Why I never trust relays (latching or not) without diode across them..?? 

What do you mean?

[mickeybellinello]

Hi!

Added the resistor but same situation unfortunely...

OK, as an experiment, what if you connect a wire from the input jack directly to the input at Cin, leave all other wiring in place.    This isn't a solution but it might help narrow down the problem to the input or the output.

So I must add a new cable that go from the jack tip to the main wah board directly?

thanks

[Rob Strand]

Why I never trust relays (latching or not) without diode across them..??

That relay is a single coil latching type,

https://www.edn.com/design/analog/4324841/Circuits-drive-single-coil-latching-relays

So the only way to get diodes in there is like,

https://i.stack.imgur.com/LVWts.jpg

If the software has gaps when switching the outputs it could be a problem.

Alternate solutions for glitches are RC snubbers across the coil.

[Rob Strand]

So I must add a new cable that go from the jack tip to the main wah board directly?

Yes just one added wire.