Lowering R1/35 to 470ohm will have a pretty significant impact on your signal level. You can theoretically increase the gain of the input buffer by increasing R7, and the gain of the output buffer by reducing R30 (wet signal) and R31 (dry signal) to compensate for the signal loss, but I'm not sure how that will affect the noise floor of the circuit. I guess it can't hurt to try. I think the most ideal solution would be to build a separate impedance converter.
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