Many musicians do not like to contend with the technical aspects of an amplifier. They would
rather leave these details to a technician. Then again, you may find yourself in an emergency
situation
( live performance )
where you may have to make a quick tube change due to a power
tube failure. In this scenario you could install a new set of matched tubes in the amp, gently
unlock the brake lever
, set the bias at
30mA
per tube
( 30mV on the meter )
, lock the brake lever,
and your done. The amp will work great, sound great, and be reliable. For those of you who
would like to tweak the amp for maximum performance, read on.
IMPORTANT:
The
bias control has a very wide operating range. It is possible to turn the bias
dial to the point where the power tubes exceed the maximum current threshold for which a
particular set of power tubes is designed to safely operate. This can severely damage the tubes
and / or an amp. We recommend you closely monitor your volt meter and power tubes, and
strongly recommend you do not bias your stock power tubes any higher than
30
m
V
. This will
guarantee an efficient life span of your power tubes.
Note:
the pre amp tubes in your amp are
self biasing and need no adjustment.
The setting of the power tube’s bias is a critical factor in the overall tone of the amplifier. The
bias setting affects the distortion characteristics, harmonic content, note separation, and
headroom, among other things. Many technicians and book authors recommend a specific
amount of bias current for a certain tube type. This approach is
not wrong
, but it allows for a
very quick biasing procedure. Time is money, especially in the mass production of amplifiers.
Unfortunately, this method disregards the most important aspect of biasing
– the sound
.
A change of a few milliamperes in bias current, in a sensitive amp such as the Komet
Concorde,
will result in a noticeable difference in tone. This amplifier reacts differently for each new set of
audio tubes, even if from the same manufacturer. Therefore we recommend setting the bias by
ear.
This is an acquired art, takes time to learn, and demands a good set of ears and a lot of
concentration.
This method is more time consuming than any other method, but it’s fun to learn
and will benefit you in many different ways:
CAUTION:
Komet
Amplification is not responsible for any damage to the tubes or amplifier
as a result of improper biasing. If you have any doubt about your understanding of this
procedure, - PLEASE STOP ! - and bring your amplifier to a qualified technician for help or
servicing.
BIASING BY EAR
Start with the bias control turned all the way
down
(
counter clockwise ).
Let the amp warm up for
a minute and flip the standby switch to the
“ PLAY ”
position. Nothing should be plugged into
the input of the Komet
at this point. Disengage the bias dial’s brake lever, insert the volt
meter’s probes into the proper test points.
( continued )
Copyright 2000-2012, Riverfront Music, L.L.C. d.b.a. Komet
Amplification. May not be reproduced in any form without express written
consent from Riverfront Music, L.L.C. d.b.a. Komet
Amplification.