Originally Posted by DefQon
Man got so many questions don't know where to start.
Ok what is the purpose of having 2-6 dual or single opamps in the output stage of some vintage high end CDP's?
What is the best opamp for the I/V converter section of CDP's?
Although discontinued what can be a single suitable drop in replacement of a MC34072 opamp?
A dac which uses 4 LME47920's and 2 LME49710's can take dual or single OPA627's?
To be edited
really old CDP may have complicated, high order 20 kHz analog active filters for the "brick wall" reconstruction filter - needed because of low/no oversampling in the early DAC chips - before today's higher OS ratios, digital filtering
some may even have the RedBook deemphasis shelving filter in a op amp active filter
DAC I/V choice has many "moving parts", "best" is an engineering judgment - intelligent rolling requires taking into consideration at least DAC chip, feedback, power supply, high frequency layout quality...
the only MC34072 "discontinued" I see are the old Pb plated parts - helps to know ON-Semi is the continuation of Motorola's analog business and then you can see the product status, read the datasheet
as a 4.5 MHz bjt op amp it boasts jfet input level slew rate and a quasicomplementary output stage that swings a bit closer to the supply rails than some others of its class/generation, also has the somewhat unusually high 44 Vmax supply - check the ps V on the board before choosing replacements
but its input V noise is horrible so any jfet input op amp beats there while matching the slew rate, more modern outputs in "isolated" semi processes with good npn/pnp speed matching are easily better today if designed for low output distortion
"better" modern chips shouldn't be hard to find on all specs - just don't go crazy on GBW - I wouldn't recommend more than double the speed without an oscilloscope fast enough to see any possible oscillations in the replacement
Edited by jcx - 11/21/13 at 11:52am