… after an initial period when I got lovely sound but no echoes! The only mode that gave the right sound was Tremolo with Reverb. After checking the voltages sent by the Arduino to the SKRM module on the Eccamatic board (the three control Pots P0, P1 and P2 and the Mode selector SW0, SW1 and SW2) and found them to be working as expected I was stumped for a while 😦
Anyway, to cut a long story short, I found I needed to join the signal from the input jack to both the Left and Right inputs on the Eccamatic/SKRM board (previously I only joined to the Left input). Once this was done – success, we had lovely echoes and a quick check showed all the emulations and presets were working as expected – happy days 😀
Some sound samples will follow as soon as I get a chance to record them.
Vintage Echoes and Guitar Effects 
Any noise from the Arduino and how hot does the Arduino voltage regulator get? I’m thinking of a separate 9 or 10V regulator for the Arduino to give it an easier life.
A little noise from the Arduino but not too bad. I’m also planning to use a separate (probably 9V) regulator for the Arduino – it does feel quite hot after a while.