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O W N E R S M A N U A L
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BIASING and METERS!
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The SE34I.5 is a self biasing, self balancing design meaning there is never a need to
adjust the bias of the output tubes. The amp does it for you. It also insures that you
get matched output power from each channel even if the tubes are not matched. And
most importantly, when compared to the common "fixed bias" approach where you
adjust the bias with a bias control, this way sounds better. The reason everyone
doesn't do it this way is because it sacrifices power. So it's an issue of better sound or
more power. We choose better sound.
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If you have perfectly matched tubes, your bias meters of which there is one for each of
the two output tubes, will read the same. This is typically between 40~50 millivolts per
side. Of course different brands of tubes may read as much as 5 millivolts outside that
window.
Yes, the input tubes can effect the bias reading on the meter as well since they are
coupled to the output tubes.
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The bias meters also show what happens when the amp is at full power by dropping to
a lower figure. For example, when the amplifier is at it's maximum clean power (just
before clipping) you will see the meters move in response to the music. They will
dance between the bias point and 1/2 the bias point which is typically between 48 mills
and 24 mills. It's a nice visual indicator that lets you know if your amp is clipping.
Decware amplifiers clip so gracefully it can be sometimes hard to notice when you
have it turned up too loud. Seeing the meters plunge down below 20 mills is a certain
indication that your amp is clipping or near clipping.
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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com
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These bias meters will tell you at a
glance if your output tubes are
healthy and if they're matched. As a
completely analog device, they can
tell you other things as well. For
example, you can watch how long it
takes the tubes to warm up and
come to full bias by watching the
meters when you first turn the
amplifier on. If one tube takes a lot
longer to arrive at it's bias point than
the other tube it can be an early
warning that there are differences
developing between either your two
output tubes are the input tubes.
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