In a stereo recording system, the bias and erase frequencies of the two channels must be equal, if the production of audio beat frequencies is to be prevented. Therefore, the bias and erase power for the two channels must be derived from one common oscillator or from two oscillators which have their frequencies locked together. The arrangement shown is Fig. 16.5 can be used for the preamplifier of Fig. 16.1 only if the AC 176/AC128 pair is replaced by an AD 161/AD 162 pair and the emitter resistors reduced accordingly.




Fig. 16.5 Tape preamplifier circuit



Fig. 16.6 Variation of harmonic distortion ...

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