OP27
Capacitor C2 and Resistor R2 form a 2 μs time constant in this
circuit, as recommended for optimum transient response by the
transformer manufacturer. With C2 in use, A1 must have unity-
gain stability. For situations where the 2 μs time constant is not
necessary, C2 can be deleted, allowing the faster OP37 to be
employed.
REFERENCES
1. Lipshitz, S. R, “On RIAA Equalization Networks,” JAES,
Vol. 27, June 1979, p. 458–481.
2. Jung, W. G., IC Op Amp Cookbook, 2nd. Ed., H. W. Sams
and Company, 1980.
3. Jung, W. G., Audio IC Op Amp Applications, 2nd. Ed., H. W.
A 150 Ω resistor and R1 and R2 gain resistors connected to a
noiseless amplifier generate 220 nV of noise in a 20 kHz
bandwidth, or 73 dB below a 1 mV reference level. Any practical
amplifier can only approach this noise level; it can never exceed
it. With the OP27 and T1 specified, the additional noise
degradation is close to 3.6 dB (or −69.5 referenced to 1 mV).
Sams and Company, 1978.
4. Jung, W. G., and Marsh, R. M., “Picking Capacitors,” Audio,
February and March, 1980.
5. Otala, M., “Feedback-Generated Phase Nonlinearity in
Audio Amplifiers,” London AES Convention, March 1980,
preprint 1976.
6. Stout, D. F., and Kaufman, M., Handbook of Operational
Amplifier Circuit Design, New York, McGraw-Hill, 1976.
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