Whammerdyne Truth, Руководство пользователя

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9
Bias Drift over Time
If a tube is marginal (either old or has residual gas), it will slowly drift over the next several hours
of operation. If it borders on defective, or is outright bad, it will not stabilize during the time the
adjustments are being made. The Truth
™
amplifier measures all of the tubes in-circuit, with actual
operating voltages and currents. The old-fashioned TV-tube testers used by many resellers are much
cruder, and basically only tell you whether the tube is completely dead or not. They can’t accurately
tell if the tube has problems or is at the end of its working life.
Tubes can test “Good” or “OK” on a vintage tube tester, only to sound pretty bad in a high-quality
amplifier, or not bias at all in a fixed-bias amplifier. (It’s a little counter-intuitive, but “fixed-bias”
amplifiers actually have bias adjustments, along with bias meters.)
If you find the “upgrade” tubes are drifting over time, we strongly suggest removing them and
replacing them with the original tubes the amplifier came with. There are wonderful tubes out there,
but there are some fakes as well. The precision bias circuits of the Truth
™
amplifier show the real-
world performance of the tube; you can trust the measurements you’re seeing during the bias-setting
procedure.
If the tubes are stable (and all good tubes are), you can set the bias, check it every now and then if
you want to be double-sure, and go ahead and enjoy the Truth™ amplifier as much as you want. It
can’t be harmed by minor mis-biasing; this procedure is here so you can get the best sound, and the
longest life, from any set of tubes you install.