SOLVED Switch Popping

[TravisM]

I build the Andromeda deluxe and love almost everything about it. When I engage the switch, it pops through the amplifier. I tried adding the delay circuit described here with no difference. This starting additional testing and while troubleshooting, I noticed that the pop occurs with nothing else is connected except output jack and the amp (no input and now power). I'm a bit stumped at this point.

I posted a before pic, an after pic (not pictured is the 380R attached to the anode leg on the resistor), the circuit schematic, the board schematic and the delay circuit diagram.

 

[jeffwhitfield]

What kind of switch do you have installed? Is it a soft click switch? Or a harder one? Honestly, even with soft click switches I have a lot of pedals that still have a noticeable "pop" when engaged. Just no easy way around it sometimes...especially if there are impedance differences.

 

[TravisM]

Soft click from Tayda.

 

[TravisM]

I just tried a new switch, new breakout board and new LED and it still pops like it is its job. C27 is the capacitor nearest the output, it is a film cap, should I start there for leakage voltage?

 

[fig]

I just tried a new switch, new breakout board and new LED and it still pops like it is its job.

Would a relay circuit be of benefit?

 

[zgrav]

maybe this article from AMZ would help --

 

[fig]

maybe this article from AMZ would help --

Hey cool! That's the same link the OP posted...

 

[zgrav]

Hey cool! That's the same link the OP posted...

If at first you don't succeed, keep repeating that mistake.

 

[TravisM]

Would a relay circuit be of benefit?

I'm not sure. That's why I'm asking for help.

I did just measure across the output jack and while switching I can see a 10-15 mV spike across it. I'll have to check that against another pedal to see if it is normal and expected.

 

[TravisM]

Definitely more voltage across the output jack than I see on a quiet pedal when switching.

 

[mdc]

First thing, I'd try disconnecting the LED and see if that solves it.

What are you plugging into? Is the switch pop consistent across multiple amps/interfaces/etc?
Have you checked DC leak from whatever you're plugged into?

Have you tried tapping the board with a chopstick/etc to see if there's a particularly microphonic component?
Are you getting any significant mechanical noise from the wire that goes from input to switch?

You could try lowering the values of R2 and R40 to see if that helps. In the AMZ schematic you posted, try raising the value of the cap to ground from 10u to 22u or higher.

Try using shielded wire from the input to the switch and see if that help at all.

 

[mdc]

Definitely more voltage across the output jack than I see on a quiet pedal when switching.

that 2U2 at the output could be really leaky? If you have a high-ish value film cap (220n or 470n or something) try swapping it for that and see if it helps.

 

[TravisM]

First thing, I'd try disconnecting the LED and see if that solves it.

Didn't help

What are you plugging into? Is the switch pop consistent across multiple amps/interfaces/etc?

Vox AC4, Fender Princeton Reverb, Yamaha THR10II. It is there but the volume of the pop is different.

Have you checked DC leak from whatever you're plugged into?

I measured a significant DC leakage from the input on the AC4. Thanks for suggesting that.

Have you tried tapping the board with a chopstick/etc to see if there's a particularly microphonic component?
Are you getting any significant mechanical noise from the wire that goes from input to switch?

No change when tapping.

You could try lowering the values of R2 and R40 to see if that helps. In the AMZ schematic you posted, try raising the value of the cap to ground from 10u to 22u or higher.

Try using shielded wire from the input to the switch and see if that help at all.

TBD

 

[TravisM]

that 2U2 at the output could be really leaky? If you have a high-ish value film cap (220n or 470n or something) try swapping it for that and see if it helps.

Replacing the 2U2 fixed the pop for the THR and Princeton! Thanks for your suggestions. Now to dig into the Vox to find the source of the DC leakage.

 

[TravisM]

So this is almost an entire year later and I just added a 100nF cap on the input to clear up the remaining DC I was seeing and now this pedal is even more quiet than from just changing the 2U2 alone. I have put it back on my board after it collecting dust for a year and it has been nice to change some of my dirt section up.