23
7. TUBES
7.4. Replacing the tubes
Driver tubes
Replacement driver tubes require no adjustment.
Output tubes
General procedure:
1.
Switch off the amplifier and allow it to cool down for 10 minutes. Remove
the old tubes and fit the new ones.
2.
Before you switch the amplifier back on, turn all BIAS adjustment screws
(see chapter 7) counter clockwise (this greatly reduces the anode current).
These screws are ten-turn potentiometers, i.e. it takes ten revolutions to
go from the maximum to the minimum setting.
3.
Switch on the amplifier and turn the BIAS selector switch to the BIAS
position. Following the Soft-Start phase, the "minus" LED (yellow) will
illuminate at every of the four Output tubes. If from this point of time any of
the LEDs are green or red, this indicates a faulty tube that must be
replaced. After a 10-minute warm-up period, set the BIAS as explained in
chapter 7.
3.1.
Original Octave tubes.
There is no need to break in original Octave replacement tubes, as
they are factory tested and passed a 24-hour endurance test. Allow
the tubes 10 minutes to warm up and adjust them to the appropriate
setting for the tube type.
3.2.
New, untested output tubes should be allowed a longer warm up period.
You should adjust these tubes after about 20 minutes and control the
setting in the first days of operation.
7.5. Running in
All OCTAVE equipment is subject to a 48-hour performance test at the factory to break in the
tubes. The tubes are preselected for use in each particular model.
New tubes can take up to three months to run in and start sounding their best.
Daily use is beneficial in speeding up this process but is not mandatory. Continuous operation does
very little to help reduce the running-in time and is therefore not recommended.
7.6. Tube service life
Thanks to the protection circuits and soft-start electronics, the output tubes in your amplifier
should achieve a service life of up to 3 - 5 years.
Driver tubes can be used for 10 years or even longer.
Because tubes have different service lives, you will never have to renew the entire tube
complement at the same time. The facility for setting the BIAS for each output tube individually
makes it unnecessary to use matched sets of output tubes. You can replace output tubes
individually if you wish.
Some tubes require a long time (up to 300 hours) to achieve their optimum sound quality.
Depending on how long the tubes have been stored, it may be necessary to adjust the BIAS
several times in the first two to three weeks after installing them.
To Next Page
Loading...
Need help?
General
