Spectradrive with excessive hiss when treble turned up past half way

I've had it in my head now for a while that I want/need a Spectradrive. This all stems from doing a small gig (we only do small gigs!) where rather than use my Ampeg BA115 and DI from that the sound guy DI'd me straight into the PA. I was not happy with my bass tone so I thought something like the Spectradrive would be ideal to help shape the tone plus I really want to try out TC's Toneprints.

So today I went and tried it out but the treble produced a lot of hiss which when you turned up the compressor or tubedrive it actually got worse. My wallet went back in my pocket. The shop guy was not techy enough to know what might be the problem and neither am I. I've searched the forum but no one seems to have had this problem. Could it have been the Schecter bass I was using, the amp/speaker combo, which I think was a JoYo. He did use a power adapter from the shop counter and did not unpack the Spectradrive one - could there be a potential issue there?

Any help, info or advice you fab TB'ers can give, as always, is much appreciated.