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13. FREQUENTLY ASKED QUESTIONS (FAQ)
6. What is the idea of selectable gain?
It becomes difficult to adjust the volume when driving loudspeakers with sensitivities greater
than 98 dB. As the range of adjustment is limited to the lower end of the volume control, it is
difficult to adjust the volume with any precision. The gain switch is provided to deal with this
problem. It reduces gain by a factor of 4, making volume adjustment easier and reducing
background noise at the same time.
7. What cables are suitable for tube power amplifiers?
The cable manufacturers are now offering cables that have supposedly been designed spe-
cifically 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 amplifiers are better able to deal with these characteristics than
transistor amplifiers. The only exception would be in the case of a tube preamp to power amp
interconnect cable longer than 5 metres. In this instance, a low capacitance cable is advisable.
8. Why are balanced inputs rarely seen on integrated tube amplifiers?
Unlike transistor amplifiers, it is not possible to design balanced (or bridgeable) tube power
amplifiers. You may come across an occasional "quasi-balanced" tube power amp, but this
makes little sense when you think about it, because it is complex, and tube tolerances make it
difficult to implement. This is why unbalanced remains the better approach for tube equipment.
It also has the added benefit of superior long-term stability.
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