Is there a reason why certain opamp would respond better to psu changes aside from psrr?
I ask because when i introduce a darlington capmx to my preamp, between the lm317/337 reg and the output opamp, the amount of improvement varies depending on which type of opamp is used.
For ne5534 the change isnt that noticeable. Same tonal balance, slightly more bass.
For opa134, opa1641, tl071, the capmx has a dramatic effect- their sharp treble is replaced by the much familiar jfet 'fuzz'. That is the treble becomes round and along with that the bass is now prominent.
No doubt this needs to be perceived as an improvement. Im wondering why is it that these opamps are so much more receptive to the capmx than the ne5534 and if theres some complex interaction going on with their jfet input and the bjt capmx, or its just that they have lower psrr than 5534.
I ask because when i introduce a darlington capmx to my preamp, between the lm317/337 reg and the output opamp, the amount of improvement varies depending on which type of opamp is used.
For ne5534 the change isnt that noticeable. Same tonal balance, slightly more bass.
For opa134, opa1641, tl071, the capmx has a dramatic effect- their sharp treble is replaced by the much familiar jfet 'fuzz'. That is the treble becomes round and along with that the bass is now prominent.
No doubt this needs to be perceived as an improvement. Im wondering why is it that these opamps are so much more receptive to the capmx than the ne5534 and if theres some complex interaction going on with their jfet input and the bjt capmx, or its just that they have lower psrr than 5534.
What is Capmx? Do you mean a capacitor multiplier? mx/mux/mpx are abbreviations for "multiplex(er)", mul/mpy are abbreviations for multiply.
I think schematics would be useful to understand your several circuit topologies.
I think schematics would be useful to understand your several circuit topologies.
It would be easy to test the hypothesis "opamp PSRR is the only difference".
Just install an RCRCRCRC ladder filter between the opamp's power supply pin, and its supply node. Include a jumper or switch that lets you bypass the ladder filter. Choose "R" such that (5 * R * OpampSupplyCurrent) is less than 200 millivolts. Choose "C" such that (C * R) is greater than 33 milliseconds.
Now repeat your experiments with different opamps and with darlington capacitance multiplier in/out. Do them (A) with the filter bypassed; you should get exactly the same results as before. Now do them (B) with the filter NOT bypassed. If they now all behave identically, you KNOW that opamp PSRR is the reason.
Just install an RCRCRCRC ladder filter between the opamp's power supply pin, and its supply node. Include a jumper or switch that lets you bypass the ladder filter. Choose "R" such that (5 * R * OpampSupplyCurrent) is less than 200 millivolts. Choose "C" such that (C * R) is greater than 33 milliseconds.
Now repeat your experiments with different opamps and with darlington capacitance multiplier in/out. Do them (A) with the filter bypassed; you should get exactly the same results as before. Now do them (B) with the filter NOT bypassed. If they now all behave identically, you KNOW that opamp PSRR is the reason.