On RIAA Equalization Networks

Most current disk preamplifiers, including some very expensive models, have audibly innacurate RIAA equalization. This severely limits any conclusions that can be drawn from A/B testing of such preamplifiers. These errors are due in part to the perpetuation in print of incorrect formulas for the design of the RIAA equalization networks commonly employed. Other factors include the existence of an uncorrected high-frequency zero too close to the top of the audio band in many noninverting designs, and failure to take adequate account of the limited available loop gain. The situation is surveyed, and tables taking into account the above problems are given for the design of both inverting and noninverting RIAA deemphasis and preemphasis circuits. Examples are furnished to illustrate the various configurations.