So Just How Quiet is Your Phono Stage?
You may be in for a surprise: actually not that quiet! The reason of course is that the cartridge inductance and resistance dominate the noise in any decent phono amp. To get the best in terms of noise performance, you really need to keep the input referred noise voltage and noise current to a minimum.
The spread sheet below rests very heavily on one pulled together by Stuart Yaniger (there’s a link to his original in the spread sheet) which in turn is based on the National Semiconductor ‘AN104 Noise Spec’s Confusing?’ published in the early 1970’s if my memory serves me well – also linked to in the spread sheet.
I’ve added the facility to enter the noise voltage and noise current for up to 5 opamps (or discrete input amplifiers). The spread sheet then calculates the total noise, taking into account the cartridge and amplifier parameters along with the RIAA gain which of course changes with frequency. What quickly becomes apparent is that even with a phono amplifier with say -90 dB noise floor reference 3 mV, you will not get better than -70 or -71 dB once you connect a typical phono cartridge ref 3mV input.
ONLY ENTER DATA IN THE GREEN SHADED CELLS AND NOWHERE ELSE!