~ RIAA–1 Configuration Calculator ~

 

Calculates the component values to make a passive 'lumped' or 'all in one' RIAA replay equalisation network of my type RIAA-1 as shown in this pdf and the schematic below ~ With R1 connected parallel to C1 the 4 terminal network can be used as a 2 terminal type which develops a voltage across it or current through it depending how it is driven and terminated

Correct equalisation using this 4 terminal network is only obtained with 0Ω source and ∞Ω load so 'perfect' amplifiers are required either side of the network but it can incorporate a resistive source Rs if R1 is reduced by Rs ~ A resistive load RL will appear in parallel with R1 so the value R1–Rs can then be increased to accommodate RL

Thus a single adjustment of R1 for the 4 terminal network can correct for both Rs and RL and is often required in practice where amplifiers have output loads and input bias resistors ~ It is also possible that the amplifier impedances are such that the calculated R1 does not need to be changed

T3  µs	T2  µs	T1  µs	Pre-populated for RIAA but can be changed
ƒ=   Hz	ƒ=   Hz	ƒ=   Hz	Calculated –3dB corner frequencies for each T
The table below allows one component in each row to be changed and accurately calculates the other 3
R1  kΩ	R2  kΩ	C1  nF	C2  nF
R1  kΩ	R2   kΩ	C1  nF	C2  nF
R1  kΩ	R2  kΩ	C1  nF	C2  nF
R1  kΩ	R2  kΩ	C1  nF	C2  nF

The 2 terminal or current driven networks are often used in negative feedback loops and have been for many years long before transistors and op-amps because when driven from a lowish output impedance and terminated into a resistive load RL the current through the network has an inverse RIAA or RIAA record characteristic

The rising current with with frequency develops a voltage across RL which could be a cathode [or emitter] load or part of an op-amp feedback loop and reduces the gain of the amplifier in accordance with the RIAA or BS1928 ~ Depending on the quality of the amplifier and the feedback topology used you may get acceptable playback of vinyl records

I refer to the 2 terminal networks as current driven because that is how I often use them ~ Not in a feedback loop around a voltage amplifier but as a load on the output of a Transconductance amplifier which could be the collector of a transistor with un-bypassed emitter resistor or the anode circuit of Cascode or Pentode where the current develops the equalised output voltage across the network As shown here ΐ

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