Emu XL-7 & MP-7 User's Group

Hi,
Ive just received my new headphones and to try them out i plugged 
them into the XL-7.
Well i happened to stumble across this..
I had all the track volumes down via the 16 knobs on the left of the 
unit. It was playing back a seq then i turned up the master volume to 
be greeted by a loud poping and the tracks would break through as if 
id cranked up the idividual volumes!!
It only happens with the first quarter turn.
Then if i increase one of the tracks volume to say about 2 the 
problem dissapears.
Then i tryed it with other presets, the same problem :o(
Can someone else try this to see if i have a hardware problem?
Ive been having problems with notes being cut off as well..
So select a bts preset on any track. Set if off playing say 4 parts 
(E1, F1, F#1, G1 etc..)turn down the track volume. Turn down the 
master volume and increase.
The problem is erractic, fast or slow movement of the knob set if 
off. Higher tracks seem worse, but lower ones do it as well.
Also happens with normal presets.
I realise you wouldnt use the unit like this, but im wondering if it 
is connected with the other issues i have wih the unit
Ive just reset the unit = same problem
Ive just re-downloaded the OS (v2.0) = same problem
Arghhh!

Gonz