Add slam switch to Multiplex Delay

[jnash85]

I am building a 1776 Multiplex delay. I would like to add a momentary "slam" switch that would engage the repeats on head 2 at a present level (either by an internal trim pot or an external pot). I have seen this done before but  have never seen how to integrate it into the circuit.

[slacker]

Going from this schematic, try this.

http://1776effects.com/wp-content/uploads/2015/03/Multiplex-Build-Doc-1.7.pdf

Connect one lug of a SPST switch to lug 3 of the mix pot, connect the other switch lug to the clockwise lug of your pot or trimmer, connect the wiper of the pot/trimmer to lug 3 of the FB pot. You'll have to experiment with pot values to find something you like.
There will be some interaction with the setting of the FB pot but it should do what you want.