4 Pole Butterworth high pass filter using TL072

[jimladladlooklike]

Thanks Antonis, I did wonder whether it would degrade the signal.

I decided to rebuild the circuit to add space for a pull down resistor on the output. It also meant I could socket the 1k input and 470r output resistors to see if increasing the value made a difference to the popping/degraded the signal. I increased them to 10k each and heard no difference either to the popping or the signal, so eventually went with the original values here.

Not pictured on this layout is the LED wiring, for which I have implemented the previously suggested combination. For this I used 2 x 47k resistors. The negative leg of the 10uF cap is connected to permanent ground.

I'm struggling with what to do next

[antonis]

I can't see a pull-down resistor on input..

[jimladladlooklike]

Oh but there is one 

7F to 7N

Or have I messed that up??

[jimladladlooklike]

My mistake!

Said pull down resistors should go from the "outboard" leg of the 220nF cap to ground, is this right?

[antonis]

Absolutely right..!!

Pull-down resistors pull down caps "floating" leg..
(which always faces circuit's outwardly..)

[jimladladlooklike]

Got it. All sorted. Thank you!

However, I still have popping...

[antonis]

Don't get me wrong but, if pops persist after all those "remedies", maybe it's time for an ENT visit..

[ElectricDruid]

(which always feces circuit's outwardly..)

Always important to keep an eye on which way the faeces are flowing...

[antonis]

Late night here, Tom..

[Fancy Lime]

(which always feces circuit's outwardly..)

Always important to keep an eye on which way the faeces are flowing...

And to duck before they hit the fan.

[antonis]

You both guys are tragic, OK..?? 

[jimladladlooklike]

Lol. Great craic.

My latest attempt at fixing this saw me changing the de mont/guyatone footswitch to a gorva one. I thought maybe with all the wiring and rewiring (and the weird solder lugs on those switches) I might have damaged it slightly. Anyway, still no dice. But there must be DC leaking from somewhere right? So maybe it's worth swapping out the input, output and LED capacitor.

I must not be defeated by this....