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RE: OPA2134 vs OPA2604 vs OPA2107

Posted by madisonears on December 23, 2016 at 20:06:07:
Call it what you will, but you get the idea that the 2134 leaves something out of the signal, while the 4562 adds something to it. I see using them together as an opportunity to extract the best balance from both. Coherence between the bands is determined by filter configuration, not parts. Coherence within the bands is the result of which parts are used. I used 4562 for input buffer and high pass, 2134 for low pass. You'll need to experiment. Do you use sockets or solder direct? You might consider sockets for experimentation, then direct solder the final configuration.

Of course, everything needs playing time to settle. Not sure it's a hundred hours (seems to be a number regularly stated but seldom confirmed), but mine played for months.

You must be aware that the passive parts produce sonic effects as well as the opamps. I have found filter component caps and resistors to contribute, especially in the high pass section. Hint: Wima caps, although good, are not the ultimate solution, primarily because they have magnetic leads, as do most cheap metal film resistors. Even the power supply caps can make a difference. Ultimate fidelity is a complex problem, with no simple solutions. Fiddling with opamps is only a start, but it's better than doing nothing. Don't neglect power supply bypassing and decoupling of faster opamps. You can add a .01uf cap right across pins 4 & 8 on the bottom of the board.

Peace,
Tom E