~ 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 to 'ground' end of C1–C2 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 for the 4 terminal network is normally only obtained with 0Ω source and ∞Ω load suggesting perfect amplifiers are required either side of the network ~ But this 4 terminal can incorporate a resistive [no C or L] source Rs if R1 is reduced by Rs ~ A resistive load RL will appear in parallel with Rs+R1 so the total Rs+R1 can be increased to accommodate RL

An adjustment of R1 alone can correct for both Rs and RL and is often required in practice so after obtaining initial values of R2 C1 and C2 with your chosen value of R1 you can select a standard value for C1 or C2 or maybe both and accept a slight change in R1 and maybe R2 ~ The default values shown here are accurate enough especially if R1 is adjusted for Rs and RL or RL and Rs just happen to work

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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