Marshall Valvestate AVT 100 Problem

v.e.r.b.a.l

I've had a Marshall Valvestate AVT 100 for a good few years now, but in the last few months the "Clean" channel has gone a bit weird. Both "Overdrive 1" and "Overdrive 2" sound fine as always, but the "Clean" channel sounds like it's muffled - like it's sound coming from the apartment above you, or underwater almost!! This is even when putting the tone to full on both the amp and the guitar.

I've tested out loads of different leads and a few different guitars, but it's the same for all. Any ideas? I hope it's not an electrical fault. I don't know if I can afford leaving it in somewhere to be fixed...

artvandulet

Seeing as you've had it "for a good few years now", I would guess you need a new valve. The AVT100 has one 12AX7 preamp valve in it.
This is a cheap fix and not a big deal at all if it is indeed the valve that needs replacing.

v.e.r.b.a.l

That's what I thought as well, but couldn't figure out where the tubes were. I asked in the shop I bought it in and he explained to me that the Valvestate series don't actually use valves or tubes. The sound is simulated electronically.

This was news to me, so I checked it out in the handbook and low and behold!

"Advanced Valvestate Technology, or AVT for short, is a major step forward in hybrid amplifier
design which is exclusive to our new Valvestate 2000 (VS2000) Series of amplifiers. It has evolved
from the original, critically acclaimed Marshall Valvestate technology, but is improved so that it
emulates even more closely the feel and response of the classic Marshall all-valve power
stage...without using valves."

http://www.marshallamps.com/downloads/files/AVT100%20hbk.pdf

Anyways, this fills me with a lot of dread, because if its not something simple like changing a valve, then it might be electrical. Ugh...

Anyone with any ideas?

seriousfizz

I think that part in the manual (and the guy in the shop) were referring to power tubes. A true valve amp has power tubes and preamp tubes.

I wouldn't have been totally sure myself, but judging by artvandulet's post, there is a preamp tube in your AVT. This can be replaced! You could always open up the back and take a peek, if you're not sure yourself.

v.e.r.b.a.l

Right-o! I'll have a look and see what I can find in there...

artvandulet

Verbal, as I said already, there is one 12AX7 PREAMP tube/valve in your amp.
This could be your problem.

Btw, 2nd paragraph of page 4 of that manual you linked to, for the record!

v.e.r.b.a.l

Oh right... Should have probably read the whole thing!! :rolleyes: