PedalPCB HAARP, is it possible to substitute R17 5.6K input buffer resistor?

K

koolimy

New member
Hi, I bought the PCB and parts for the HAARP arpeggiator, but I noticed that I don't have a 5.6K resistor that would go in R17.
Reviewing the schematic, it's the resistor that goes to ground along with a 1uf cap on the negative side of the input IC (TL072).

I was wondering if it would be possible to replace that 5.6K resistor to something like a 4.7K or 10K?

It seems like changing R17 would change the gain from around 2.67 to 3.19 (4.7K), or 1.5 (10K). The high pass filter frequency would change from 28.4 to 33.9 (4.7k) or 15.9 (10k).

Does the FV-1 chip need a specific input gain to function properly?
Sorry if this is disjointed, I am still quite new to this pedal hobby so I don't understand the concepts enough.

Thanks!

HAARP
 
Changing from 5.6k to 4.7k is a difference of 6dB. That's significant, but not huge. There's probably more variation between quiet and loud playing or vintage single coils and hot humbuckers. You could also drop R16 to 12k and get within 1dB of the stock circuit.
 
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