I have a valvetronix 40+, which I am quite happy with. However, I've run into a problem when I try to run my pedal board in front of it--the sound gets really cruddy and distorted, even on the Fender clean amp models. The board is a Behringer PB1000--cheap, but it runs fine in front of other amps. The problem doesn't occur if I run two or three pedals on their own directly into the amp. Is there some kind of buffering issue going on--or would it be electrical? I did check to make sure there were no dead 9 volts in any of the pedals.

Thanks. I have many pedals, but as most of the on-board effects are quite good, I really only want to run: 1) digital delay (I bought an Echo Park as I find the vt+ delay quite weak; 2) overdrive (as a lead boost); and wah. Of the three, I believe only the wah has true bypass option, so I'll check out the option you suggest.

This could just be down to the quality of wiring/pedals, but the front end of Valvetronix amps are DSP (digital signal processing). Whilst results will vary depending on pedals used, generally speaking the Valvetronix amps are sometimes not overly 'fond' of external pedals (compared for example to the AC15/30VR which have a different non-modeling front end, and were specifically designed with external pedals in mind).

Best results will be to use the internal pedals and if you need anything more, just keep these to a minimum - as you found, 2-3 pedals on their own aren't usually a problem. Remember too that time based pedals (delays, modulation) are better suited in an FX loop, not at the front end, anyway - unfortunately, none of the VT+ variants comes with an FX loop. If you want to add an FX loop, there is a non-Vox mod/kit option at Valvetronix.net, designed by 'Retrobob', but this will invalidate your Vox warranty.

Thanks. I'll troubleshoot individual pedals, cables, etc. The problem is actually a recent one--I didn't notice the issue with the board previously--some darkening of tone but not undesirable distortion, almost as if signal was having difficulty getting through. I usually run the amp on the AC30 green model--have never tried it in manual. Will do. I'll also run the wah on its own into the amp and see if that's the source. The Echo Park and OD808 aren't the cause...

You're welcome - glad to help