[quote name='warwickhunt' post='185106' date='Apr 25 2008, 09:51 AM']Hey Lee.
If you're talking one valve (12ax7 / ECC83) in the preamp I have to confess that from experience there is sometimes not a huge amount of difference in the tone between valves. The EBS may be different but I've had 4 valve fronted amps and I bought a whole selection of tubes at one point (sorry they've all gone) to try in the front end and the difference was negligeable! I had H&K, Groove Tubes, Rubies, EH, Mullard etc and even though I tried all of them in all of the different amps over the course of a couple of years they didn't make enough difference for me to justify one over the other.
I'm not saying that would be the case in all amps or that valve amps wouldn't be affected to a greater degree by the choice of preamp valve(s) but in the case of a single valve in the front end of a basically solid state amp I didn't notice any massive difference.
I could be wrong (step in and correct me techies) but I have a feeling that many of these valve fronted amps actually don't send 100% of the signal through the valve, which could account for the lack of obvious difference [/quote]
i'm pretty sure the signal does go through the valves since it is a valve pre amp unless the circuit shorts really badly i don't see how they would and why you'd go to the effort to make the signal not pass through them