Upgrading Rolls mini mixer MX-28 to get an Hi-Fi sound

[rantony]

Hello everybody,

I have a mini Rolls mixer, model MX-28. It's a very cute and useful product. It's very small, so I can put it on the top of a keyboard to monitor my sound. I like it a lot, but it has a flaw. When I feed it with a bass sound, it won't reproduce every details and some warmness is lost. I would like to mod it to get a better frequency response and thus a more accurate reproduction.

Here is a link to the schematic (it's public):

http://www.rolls.com/pdf/M_MX28.pdf

As you can see, it is using five BA4560 opamps. The 120pF (x8) and the 50nF (x1) capacitors are ceramic. I thought about changing the opamps for better ones, and changing the ceramic capacitors for mica's. What do you think about this ? Any suggestions for the opamps ?

Another question I have is about the power source: The unit uses 12V. Isn't it a limitation ? Aren't opamps giving better results when they're powered with 18V or 24V ?

Thanks for your help !