Add reverb and slave powered remote to an one channel amp with fx loop

[mfunky]

Thought I'd post this one, as it may be useful to some of us - nothing sensational, but something quite handy!

I am in the process of adding a reverb to a vintage marshall. I want to mount the reverb (a rub-a-dub) in the back of the amp and connect it to the amp's FX-loop. I want to be able to either use a manual switch on the reverb to enable/disable it and have an LED on the reverb to see which state it is in.

I want to add a phantom powered footswitch with LEDs for reverb and channel select. I want to use a TRS (stereo) 1/4" standard jack/cable for this. If the cable is inserted, the internal LED and the internal reverb switch and LED will be bypassed.

I am using two 5V RY5W-K (sometimes called RY 05W K, a Finder 30.22.7 5V will work as well), some vero, two 220 Ohm resistor and standard yellow and red LEDs for this. With the resistors in series with the LEDs and the relay, the voltage and current for LEDs and relays are in acceptable ranges (even if no LED is used, e.g. if I use my looper instead of the switch):

Measured values with R=220R, yellow LED:

Voltage over Relay with yellow LED in series: 3,24 V (enough to switch!)
Voltage over LED: 1,99 (within specs)
Current through LED: 18,17 mA (within specs)
Voltage over Relay when using a footswitch w/o LED or a Looper: 4,01 V (still below the acceptable 5V)