W W Biffta wrote:
hmm. really hard to say without details. short answer is yes, stick a preamp inbetween the main amp and the sub.
long answer, question is what outputs are you running the sub off? is it one of those prefiltered dedicated sub outputs for running 2.1 mode dolby? not going to be the tape loop cos the amp main vol wouldnt effect that. ive had amps with a pre amp stage output, would make sense if the main vol works the sub too. if it was an a/v amp you would be able to control the levels to the sub so i assume its not one of them. sometimes you can run the sub off the speaker out, but they are generally not powered subs and you probably shouldnt run a powered one off it. tbh i cant think why the sub wouldnt have controls on it, but my suggestion would be run a preamp off the tape loop output and the sub off the preamp. no scratch that my advise is to get a decent subwoofer with controls on it.
You could try this but it would be just as simple to replace/ update the equipment. Adding extra pre-amplifiers (ie volume controls) can also induce ground loops which give a nice annoying 'hum'.
There are subs that are designed to have a 'high level' input, these simply plug in to the amplifier's speaker terminals as you would connect speakers, then you connect your speakers to the sub's specific terminals.
I use this type between my TV's speakers as they are shite.