T O R I I J R O W N E R S M A N U A L
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It is possible for one output tube to fail or start to fail with the other output tube being
perfectly fine. If this happens only one half of the music (sine wave) will be reproduced
and the suspension of your loudspeaker will be the only thing reproducing the other
half. The most noticeable symptom of this is that the channel will drop to about 5 watts
and have high amounts of distortion.
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Input tubes - the 6922 input tube consists of one half of the tube as the phase splitter
and the other half as a gain stage. The two halves are direct coupled. This means no
capacitor is used resulting in no phase shift so the perceived speed and honesty of the
amplified signal is communicated rather well above the norm. Symptoms of problems
occurring in the input tube could be lower power, increased distortion, drifting
loudness levels in that channel, noise, hum, lower gain, softer dynamics. If you’re not
sure, simply install a new input tube and see if you hear a big change.
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Clearly, the best way to know if any of the above mentioned tubes are compromised is
to simply have a complete set of new tubes that are verified good. Decware would
obviously be your first choice for getting the best quality tubes for your amplifier.
Anyway, when you have a complete set of replacement tubes, you can fix 95% of any
problems your amp might ever develop over its lifetime.
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To find out if one of the tubes is compromised in some way, first you must determine
which channel has the issue. One of the things we do when troubleshooting the
sound of an amplifier is to listen to only one channel at a time, and do so by switching
the interconnect cable between channels. This means we would take the left channel
interconnect and switch it manually between the left and right channel of the amplifier
and compare the sound. Doing this will let you hear which channel has the problem.
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Once the channel with the problem is identified, you simply change either the EL34 or
the 6922 for that channel and see if the problem goes away. In rare cases you may
find the problem persists even after you have replaced both EL34’s and the 6992 in the
problematic channel. At this point to know if the problem is the tubes or the amp, take
all the tubes in the left channel as they are, and swap them with all the tubes in the
right channel. If the problem actually is a tube, the issue should switch sides. If the
problem does not switch sides, then it is either the source, preamp, cables or amplifier.
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In summary typical tube problems can result in: Lower power, Higher Distortion, Noise,
Hum, Channel imbalances.
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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com
