TL72IP or TL72CP question, and popping apostle.

[ElectricDruid]

C = Commercial (std temp range)
I = Industrial   (wide temp range)
M = Military (wider temp range)

Other specs can vary for M.

Just for completeness, you sometimes see "E" for "Extended" too. That sits between I and M.

[antonis]

I tried to add a 10n film cap as described in reply #16. I desoldered the legs circled in blue, and soldered a cap on the legs, leaving the pads empty :

I have a signal in bypass, it shuts down when the effect is engaged, unfortunately no sound.

A close photo of your build (both PCB sides) should help a lot..

[duck_arse]

I mean—technically yes but it's much easier to say it blocks DC.

I looked for "input capacitor" on wikipedia

Try "coupling capacitor": http://www.learningaboutelectronics.com/Articles/What-is-a-coupling-capacitor

a cap in series will block DC - so often a coupling cap is called a blocking cap.

[eh la bas ma]

A close photo of your build (both PCB sides) should help a lot..

Thank you, but I don't think pics will be needed. I fixed my mistake : The remaining R3 pcb-soldered leg is grounded, so I needed to add a jumper on the empty R3 pad to restaure the signal path... quite simple, let's say that I was probably tired last night.

Thanks for the suggestion, I can't really notice anything obvious differing from before, and I guess that's a good thing.

Edit: oh ! it sounds like the popping is much less audible, it's kind of silent now...  Aahyyaa ! Gloire ! Glory to Antonis !
Blocking DC is effective on popping noises in some cases, I guess ?

I noticed the volume pot is located before IC1 TL72 on schematics. I'm used to see Volume pots at the end of circuits. I wonder what's the function of IC1 ? Is it a cabsim circuit ?

[FSFX]

I wonder what's the function of IC1 ? Is it a cabsim circuit ?

IC1A is just a unity gain buffer between the volume potentiometer and the 'Sallen-Key' 4.82kHz lowpass filter implemented by IC1B.
Having the volume pot like that with the buffer and filter you have a very low output impedance and a high end cutoff frequency of almost 5kHz.

[Rob Strand]

Having the volume pot like that with the buffer and filter you have a very low output impedance and a high end cutoff frequency of almost 5kHz.

FWIW, -3dB cut-off will end up lower than 4.82kHz, around 3.10kHz.

[FSFX]

FWIW, -3dB cut-off will end up lower than 4.82kHz, around 3.10kHz.

As Rob says. 4.822kHz is the -6dB (half-voltage) cut-off point and around 3.1kHz is the -3dB (half-power) cut-off point.

If you are really interested, then here is the actual calculated response:

[antonis]

Blocking DC is effective on popping noises in some cases, I guess ?

Actually, it's effective on more than just popping issues cases..

[bartimaeus]

Just be careful in case you buy the TL072H. Apparently the H version is noisier and might not even be JFET: https://www.modwiggler.com/forum/viewtopic.php?t=242526