Mod RME Quadmic I?

[opnordahl]

I am considering modifying a RME Quadmic. The microphone preamp uses the JRC 4580 (NJM4580) op amp both in the gain stage and the output stage. Would OPA1612 be a drop in replacement? It seems like this has been done in a very similar modification of the pre amp section of RME UFX link: RME UFX mod

The preamp uses standard Su'scon (SL series) capacitors all over the board. At least the input and output caps could maybe be replaced by Nichicon MUSE ES 100uF/25V bypassed with WIMA MKP 0.1uF or Vishay MKP1837 (or other alternative). The MUSE ES are non-polarized so there might be other low ESR polarized alternatives (maybe Nichicon Fine Gold).

The gain stage uses 2SA1084-E transistors. These are maybe ok?

The PSU uses Lelo RXJ series (105dg) capacitors. These could be upgraded to Panansonic FR. But I do not know if this is needed.


Output section with 4580 op amps:

Gain section with volume, phanthom, Lo-Cut, phase. 4580 op amp and 2SA1084-E transistors

PSU

Input Su'scon SL standard series capacitors

Distortion measurement using a Motu 828 (2024)


Any suggestions?

 

[JohnRoberts]

What is the problem you are addressing?

JR

 

[opnordahl]

Do you think the OPA1612 would work as a drop in replacement for the JRC 4580 (NJM4580) op amp and sound wise how many of the caps should be replaced (lower ESR caps)? The amp is old and the measurement on the different channels are quite different so some of the capacitors probably is a bit dried out.

The JRC 4580 is not the best op amp so I am trying to squeeze out some extra juice of the mic preamp.

 

[opnordahl]

Also, should I replace the 2SA1084-E transistor with something else?