Recommendation on use of series K157UL1 microcircuits

The series of K157UL1A/B microcircuits are low-noise two-channel playback preamplifiers for stereo tape recorders. The characteristics of the K157UL1A microcircuit are noise voltage V sub n, in = 0.46 uV and noise current I sub n, in = 120 nA referred to the input, in the 20-20,000 Hz frequency range, based on measurements and calculations with the aid of spectral density curves. The characteristics of the K157UL1B microcircuit are somewhat worse. The K157UL1A microcircuit can be used in the playback channel only when its transmission coefficient is at least 50, otherwise the preamplifier becomes unstable. Its resistors and capacitors must be selected and matched for necessary gain and time constants at the various tape speeds. This microcircuit can be considered for use in the recording preamplifier and final amplifier stages.