steve, do i assume correctly that you first noticed the hiss when you started using the horn speakers? if that is so, then you are the victim of their efficiency. i've noticed the same thing with an sp10 which is very sensitive to tube noise. one way to solve the problem is to attenuate the output of the preamp. for example in order to get remote control, i inserted a passive volume control (think placette or crook) and this did the job quite nicely. there are probably other ways of attenuating the output of the preamp but i'm not a technician and can't help you.