Well done. I guess you have not had any trouble with noise being introduced into the signal? Im guessing not.
You may consider using a little jack in place of the protoboard.
You could use 1/8in phono jacks. That would allow for easier plug and play, without a bunch of soldering involved.
That way you can "plug in" different cap varieties. You could also replace the caps in the perfboard with female headers so you can plug in different caps without having to solder while tuning everything. This will allow you to use the switch to compare cap types and specs side by side.
You may consider using a little jack in place of the protoboard.
You could use 1/8in phono jacks. That would allow for easier plug and play, without a bunch of soldering involved.
That way you can "plug in" different cap varieties. You could also replace the caps in the perfboard with female headers so you can plug in different caps without having to solder while tuning everything. This will allow you to use the switch to compare cap types and specs side by side.