Volume boost when replacing a resistor with a pot

sticky1138

Well-known member
I'm adding a dry-chorus-vibrato blend to a MBP Touchstone (EHX Small Clone). If you take out the 22K resistor, it turns into a vibrato, so I'm putting a pot in its place for the best of both worlds.

With an A100K pot I'm getting a nice taper - vibrato fully clockwise, chorus at noon, and fully dry at CCW, but there's a volume boost as you approach dry, louder than both the chorused signal and the bypass signal.

I have pins 1 and 2 on the resistor pads, nothing connected to pin 3. Do I need to add a cap or something to tame that volume jump?
 
I'm adding a dry-chorus-vibrato blend to a MBP Touchstone (EHX Small Clone). If you take out the 22K resistor, it turns into a vibrato, so I'm putting a pot in its place for the best of both worlds.

With an A100K pot I'm getting a nice taper - vibrato fully clockwise, chorus at noon, and fully dry at CCW, but there's a volume boost as you approach dry, louder than both the chorused signal and the bypass signal.

I have pins 1 and 2 on the resistor pads, nothing connected to pin 3. Do I need to add a cap or something to tame that volume jump?
I believe this is due to how the op amp works, you're increasing the gain as you lower the resistance going into it and once you go below 22k you're boosting the signal. The way its done on the julia chorus is sort of adding a pot to vref so you're killing off some signal that way instead of changing the gains so a configuration like that might work better for you.

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