I use a Vox AD50VT 212 and was thinking of adding a small tubed pre-amp between the guitar and amp to see what effect it would have.

Anyone tried this and how does it sound? I was thinking that it might add a bit of warmth to the sound???
do you mean a rack mounted preamp or a pedal like the ehx black finger?
if you cranck the preamp completely and your SS a bit lower you will have a warmer sound.
But 1 or 2 preamp tubes won't have much effect on your tone.
Set the preamp to go into the FX return of the amp ( if its a rack preamp). This way you bypass the crappy modeling preamp (assuming you don't like it) and have this going on :

Guitar---->preamp----->Fx loop return (modeling amps poweramp)---->speakers
My Gear
-ESP truckster
-Ibby RG 7 string
-Mesa/Boogie Studio Preamp (Mk2C+ mod)
-Mesa/Boogie 50-50 Stereo Poweramp
-Mesa/Boogie Vertical 2x12 (C90 and EVM)
Thanks, I was thinking of a small pre-amp like the Art Tube MP Studio v3 or the Presonus TubePre - mainly used as an interface with the computer but I thought that it could also be used to warm up the tone from the amp.
OK, I'm back to this. If I want to fatten up the tone through this amp what would be better - the tubed preamp (Presonus or ART Tube) - or a preamp pedal? If a pedal is recommended which one? I am on a limited budget fir this one and it would be around £60 (eBay may be my friend!)
The tube preamp your talking about are mic preamps, and they wouldn't improve the tone from your amp. You'll need to buy an amp simulator if you wanna do this, but your amp's preamp is already an amp simulator, so why replace an amp simulator with an amp simulator?
So, unless you want to buy a high end preamp or you want to teh br00talz(wich the valvetronix can't do), I don't think it's really worth it.
Now, that's just my .2¢, if you still want a preamp pedal take a look at tech 21, they make some pretty good and affordable ones: http://www.tech21nyc.com/products/sansamp/index.html
Many thanks, Squit. The valvetronix simulation is ok but pretty basic and that is why I had hoped that by using a tubed preamp while bypassing the modded amps would provide a warmer sound from the amp. I know that those preamps that I mention can be used as DI devices and had hoped that they might just improve the warmth of the amp. I am sure that I have read of others considering this but can't get back to those threads.
However, if it is not worth wasting my money............I'll move on to something else for Christmas!
Quote by erskine

However, if it is not worth wasting my moneyChristmas!

I'm not saying you are wasting your money by buying a preamp, because a preamp has alot of uses, can be used as an headphone amp, you can bring to a jam and just plug into a P.A., that way you don't have to lug your amp, it's also good for direct recording. My point is that I think the valvetronix have a decent preamp section, so unless you want a completely different sound, it's not worth it, but that's if plan on using it only for that purpose, like I said an external preamp has alot of uses. Maybe it's worth buying one, it's definetly not a waste of money