pedal crackling when switched on

[frogman]

I have what i hope is a simple fix here. I built a box of hall reverb, soldered it up in an enclosure.Everything sounds good, but when I switch it on, a crackling sound happens. Its more of a reverberating popping that sound that doesnt happen with the reverb knob turned completely down, as I turn it up the crackle becomes more audible.

I followed the signal with a bias probe and found that it is not happening at the input jack lug/board input of the 3pdt switch and is happening at the output jack lug/board output. So the problem probably isnt on the board/pots/everything before the input of the 3pdt switch, BUT just in case, I tried swapping out the reverb pot and it still happens. Also tried swapping led's and it still happens.

Not sure where to go from here. Anyone ever experience anything similar?

[antonis]

Are the IN/OUT jack connected to GND via the metal enclosure or via their own sleeve lugs...??

[induction]

Those Belton bricks are finicky about power. I've had similar problems in a different circuit where I was using a 100 ohm resistor between the adapter and V+ (to improve the ripple filtering with the filter cap). Once I removed that resistor, it worked fine.

Your problem may be completely different. Can't really say. Measure your voltages.

[GibsonGM]

Does it crackle all the time when you have the pot up? A constant thing like a fire burning or something?

Or does it do it intermittently, loud and nasty at first, then calms down, maybe just comes back randomly?

Maybe make a video to demonstrate if you can't find the problem on your own...from the description, it could be anything from those already suggested to a bad solder connection, or even something arcing (if that's possible, don't know how the PSU is set up)...

[frogman]

Antonis:
The sleeve/ground lug of the input jack is grounded to the switch. The output jack ground lug has no wire going from the ground lug.

Induction:

Voltages:

BTDR2H:

Pin 1: 4.9V
Pin 2: 0
Pin 3: 4.63V
Pin 4: 0
Pin 5: 4.61V
Pin 6: 4.61V

78L05

In: 9.35V
Ground: 0
Out: 4.89V

TL074CN

Pin1: 4.62V
Pin2: 4.62V
Pin3: 4.62V
Pin4: 9.35V
Pin5: 4.20V
Pin6: 4.62V
Pin7: 4.62V
Pin8: 4.62V
Pin9: 4.62V
Pin10: 4.62V
Pin11: 0
Pin12: 4.62V
Pin13: 4.62V
Pin14: 4.62V

Gibson:
Its crackles only for a second when turned on. But now that you mention it, there is a sound when the reverb is turned up the whole way. Its a low hiss. Sort of like when a big muff is on and you roll the guitar volume down, but not as extreme. That might be normal though.

[Tony Forestiere]

"Iffy" contact in the foot-switch?

[frogman]

Not the 3pdt switch, just swapped a new one in and the problem persists.

[Mike Burgundy]

The hiss is probably normal.
So, it makes a "KGGgggg..." for a second when you switch it on?
Without hearing that sound, that suggests to me to be switch-pop which is then fed through the reverb.
Do you have all the usual pop-prevention in place (pulldown resistors, blocking caps...)? Power to the circuit is always ON right?

[Kipper4]

The all star reverb does this too.

[anchovie]

Seeing as the switch pop is happening on the input (hence it's a pop+reverb) - don't switch it! The input impedance of the Box of Hall is so high that you won't notice a sonic difference between true bypass and being always connected.

Keep the footswitch throw that handles the LED.
Hardwire the input jack to both the effect input and the bypass lug of your output throw, middle lug to output jack, remaining lug to effect output.
Lose any other footswitch wiring.

[frogman]

Seeing as the switch pop is happening on the input (hence it's a pop+reverb) - don't switch it! The input impedance of the Box of Hall is so high that you won't notice a sonic difference between true bypass and being always connected.

Keep the footswitch throw that handles the LED.
Hardwire the input jack to both the effect input and the bypass lug of your output throw, middle lug to output jack, remaining lug to effect output.
Lose any other footswitch wiring.

I am sort of confused by your explanation how to wire the switch. Any chance you could explain it again? Would a diagram be too much to ask?

[frogman]

At the risk of being completely wrong... is this the wiring that was described?

[antonis]

In bypass mode you ground the Effect output (which is OK..) but  - despite of mode selection - you have permanently grounded the output jack (which ISN'T OK at all..)  


P.S.
From another point of view it's definately THE cure for eliminating ANY sound...

[anchovie]

I am sort of confused by your explanation how to wire the switch. Any chance you could explain it again? Would a diagram be too much to ask?

Bear with me here - I'm at work so can't really use any drawing programs...

What I'm suggesting actually doesn't need a 3PDT, a DPDT footswitch will do, but you can use two columns of a 3PDT if that's all you've got.

Here's your footswitch in the same orientation as the diagram that you drew:

1 4 7
2 5 8
3 6 9

So if using a DPDT, 7/8/9 wouldn't be there.

Input jack goes to both 3 and the effect input.
Effect output goes to 1.
Output jack goes to 2.
LED goes to 4.
Ground goes to 5.

The result is that the input never gets switched but the output and LED do, so there's no chance of a pop having the reverb applied to it.

[induction]

The result is that the input never gets switched but the output and LED do, so there's no chance of a pop having the reverb applied to it.

On the other hand, the circuit will be reverbing everything you play in bypass, but not sending it to the output. Which means when you engage the effect, you'll hear the tails of whatever you were playing while in bypass. Instead of (or maybe in addition to) the pop, you'll hear an instantaneous reverb fade. This might be more problematic than the pop you have now, especially if the reverb is set very high. Or might not. Depends how you use it, I guess.

[anchovie]

5 stars to you - I totally missed that aspect!