When you have a sustainer in a guitar, and the output of the pickups is split (between the input of the little ruby-like amp to power the driver, and the normal guitar output) are there any issues that arise from the normal output of the guitar?
In other words, do you need a buffer or something on the normal output, or does passively splitting the pickup output work fine?
Looking at sustainer projects on the internet, a lot of them seem to use this:
(http://farm3.static.flickr.com/2520/4107858712_4483e71933_o.jpg)
If you do use the Fetzer-Ruby, I'd suggest increasing the resistor between the JFET's gate and ground to 4.7M. Then, you shouldn't need a buffer because, between the 250k-1M load that your pots put on your guitar pickups, and the 500k-1M load your first pedal or amp will probably give, you won't hear 4.7M more.