This problem seems to be pedal related.
I am using (in order) Polytune mini - TC Electronics Corona chorus - 3 leaf Pwnzor compressor. These are powered by a 1 spot power supply to a 4 way daisy chain (yep only using 3).
On a couple of occasions, approx halfway through a gig, the volume drops considerably. I bypassed the pedals and went direct into the amp and all was fine apart from no effects!
I took the Pwnzor out of the equation as it seemed the most likely culprit, last number on Saturday's gig the same thing happened. !! This is only using the chorus and tuner.
Could it be the power supply.(rated at 1700 Ma)
I am at a loss as to what to try next