Interlude - a remote-control preamplifier

interlude elektor april 1983 a remote- control preamplifier To provide a preamplifier with a remote- control facility, the first step is to ensure that all its controls can be operated by means of a DC voltage. The input selector switch, for example, could be replaced by a box of relays or by so-called analogue switches. However, relays are expensive and require heavy-duty drive circuits; con- ventional analogue-switch ICs are not bad, but they are not really good enough for a top-notch audio system. The analogue controls (volume, balance and tone) are even more difficult. An ideal solution would be to use some kind of motor-drive for the potentiometers: just think of the gimmick-value of a knob that is rotated by a ghostly hand! Yes, and just think of the (mechanical) problems. Another alternative would be to use OTAs (Operational Transconductance Amplifiers) as electronic potentiometers. Unfortunately, their performance tends to be below par. To cut a long story short: any type ...