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11. FAQ
1.
Can you operate the RE 290 when no loudspeakers are connected?
Yes. The RE290, like all OCTAVE amplifiers, is fully protected against open circuit operation,
i.e. the amplifier will come to no harm if it is operated without loudspeakers connected.
2.
How do you recognize a faulty tube?
See
troubleshooting
3.
Is there a loss of sound quality as tubes age?
No. Tubes normally sound the same throughout their service life. Our soft-start technology
contributes greatly to extending the service life of tubes. You can tell when an output tube has
reached the end of its useful life: it becomes impossible to adjust it correctly. Driver tubes
cannot be checked, but these will generally last for well over 10 years.
4.
Does the RE 290 have to have all of its tubes fitted?
In principle, the RE 290 will also operate without tubes. It is sometimes useful to do this when
testing the operation of the switching functions such as the selector switch, remote control,
etc. Of course, it is not possible to play music under these circumstances.
For test purposes, or as a temporary measure, one channel may be fitted with just a single
power tube, although its power output will - of course - be reduced. The amplifier will come to
no harm if it is operated continuously like this.
Operation without driver tubes is also possible for test purposes, although, for obvious
reasons, music playback is not possible.
5. What is the significance of loudspeaker impedance and efficiency?
The impedance and efficiency of modern loudspeakers is not an issue for OCTAVE amplifiers.
The often-quoted damping factor is not normally a guarantee that an amplifier will exert tight
control over the loudspeakers. In practice, speakers of 85 dB efficiency and above are suitable
for use with tube amplifiers. The high stability of the OCTAVE power amplifier technology even
allows the use of speakers whose impedance dips as low as 2 ohms (except for EL34 with 4
ohms)
6. What cables are suitable for tube power amplifiers?
The cable manufacturers are now offering cables that have supposedly been designed
specifically for tube amplifiers. Although such cables may be of good quality, there is no need
to use special cables with tube amplifiers. Speaker cable can exhibit high values of
capacitance and inductance, and tube power amplifiers deal with such loads better than
transistor power amplifiers. The only exception would be if you needed to use a tube pre-to-
power amp interconnect cable longer than 5 meters. In that case, a low capacitance cable
would be advisable.
