Where did you have the "mix" knob set? I have had a Carbon Copy since they first came out and have not experienced any noise from mine.
There is of course the Aqua Puss re-issue for about $150 and it has up to 300ms of delay where as the Carbon Copy has 600ms. Both pedals were designed by the same guy.
For $195 you can check out Tech 21's new Boost DLA with Tap Tempo.