Octave V 70 SE [21/33] Replacing the tubes

7. TUBES

7.4. Replacing the tubes

 Driver tubes

Replacement driver tubes require no adjustment.

 Output tubes

General procedure:

Switch off the amplifier and allow it to cool down for 10 minutes. Remove

the old tubes and fit the new ones.

Before you switch the amplifier back on, turn all BIAS adjustment screws

(see chapter 7.3) counter clockwise (this greatly reduces the anode

current). You will hear a click when the screws reach the minimum

setting. These screws are three-turn potentiometers, i.e. it takes three

revolutions to go from the maximum to the minimum setting.

Switch on the amplifier and turn the mode selector switch [No. 2, chapter

4] to the BIAS position. Following the Soft-Start phase, all 4 "minus" LEDs

(yellow) will illuminate. 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.

3.1.

Original Octave tubes.

There is no need to burn in original Octave replacement tubes. 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.

7.5. Running in

All OCTAVE equipment is subject to a 48-hour soak test at the factory to burn 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.