I'm just beginning to step my toe into the murky waters of phono stage design, and I've noticed there can be considerable variation among simple opamp-based passive RIAA designs in the series resistor value, with the pursuant changes in the other RC components. Attached are a couple of examples.
While the opamps used in each schematic have some differences -- input voltage noise among them -- they both are capable of driving low impedance loads with low distortion.
Why would a designer choose one approach over the other?
My apologies -- I'm certain this has been asked and answered many times before, but I can't seem to find or discern an answer
gtrmkr
While the opamps used in each schematic have some differences -- input voltage noise among them -- they both are capable of driving low impedance loads with low distortion.
Why would a designer choose one approach over the other?
My apologies -- I'm certain this has been asked and answered many times before, but I can't seem to find or discern an answer
gtrmkr
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What exactly is your question. Apart from differing component values, both topologies are exactly the same.
Gain of the first circuit one is a bit high, the second a bit low, but that's all a matter of selecting the right values fitting your needs.
True, but with an OPA2604 with high rail voltages which will go a long way to improving overload margin.
The way the circuit is drawn, however, with a 470k build-out resistor (R1 in Lipshitz) it will also be very noisy.
Hard to say. The only excuse for the high impedance network is the belief that a particular opamp sounds better into higher impedance loads. At some stage, a long time ago this was perhaps true.
Personally i do not like the subjective effect of high resistance in series with the signal. My current opamp riaa has no such resistor at all.
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