7. Maintenance
Valve Type : 12AT7 (equivalents : ECC81 , CV4024)
The VMPQuadPlus preamp comes stocked with brand new J.J valves.
Sebatron uses J.J (Brand) 12AT7 valves exclusively in all the currently
produced designs.These valves are favoured because of their realistic
representation of the audio spectrum as well as their low-microphony and
open-ended frequency response.Please note-valves vary greatly not just in
frequency response or sound quality but also in noise floor and
microphony.
Other recommended brands include: Amperax,Telefunken,Phillips,
JAN,National Electric,Mullard.
Valve life :
As the VMPQuadPlus is a preamp then valve wear is not as severe as
standard guitar amplifiers etc. Valve life also varies from valve to valve but is
generally three to five years with average useage and up to ten years if used
sporadically. As valves approach the end of their lifespan there usually is a
rise in noisefloor (hiss-noise) and a narrowing of the sonic bandwidth.
If useage is minimal and within 10 hours a week on average then we
would recommend valve replacement around the four to five year mark.
Heavier useage, twenty hours a week and upwards for example , we would
recommend valve replacement around three years.
One should keep in mind the fact the VMPQuadPlus is a pure
Class A design which means the valves are active even when no signal is
going through so it is a good idea only to power up for useage and not leave
the unit on for hours for no reason.This will minimize wear and therefore
increase valve life.
If possible allow approximately 1 to 3 minutes for a complete warm up
of the valves before commencing recording.This is so the valves can stabilize
in the conditions the unit is powered up in. It’s not cruicial of course and you
may wish to use the unit immediately which is fine also but there still will be a
warm up time of at least 30 secs before the valves will begin to pass
a decent signal.
Replacing Valves :
Replacing valves is easy - simply take off the lid of the unit and pull the
offending valve upwards with a slight wobble to get it out of the socket.
Plug the replacement valve into the socket keeping in mind the
orientation of the gap in the pins so that they line up correctly.
