Has anyone out there hacked their own UA5?
I'm thinking of replacing the mic preamp (surface mount chip, 4580 I think) with an OPA2134.
Would that help? In particular, I notice a fair bit of noise when I turn the gain up high.
Also, does anyone have opinions on the OPA134? I know the INA217 is the professional chip, but I'm looking at the OPA134 for a battery powered preamp as well. This is for something running off a single 9V battery. It is also pin compatable with the other opamp chips so I want to start here.
Thanks,
Richard
Where did you get the idea to do this? How did you arrive at your choice of the op-amp?
OK, whoever does this first, please post here! I haven't actually looked at the insides yet, so I don't even know which one of the Opamps is for the mics. I think one is for the phantom circuit too, so be careful to get the right one.
To answer your question, I heard about Oade's mods and thought, why not try it myself. I've also got a parallel (now stalled) project to build a simple 9V preamp box, so that's why I'm interested in the OPA134. It seems to have good performance and reasonably low DC power requirements. Oh yeah, someone on this board suggested getting samples from TI, so that's what I did. There may be other opamps (AD, etc) that work too.
So far I've only done one successful mod. I replaced the LM358 opamp in a Griffin iMic with a LMV722. I'm not sure it made any difference, but for some reason I couldn't resist the urge to mess with it. In case anyone is wondering, one trick I discovered was to use glue (epoxy) to hold the chip in position before soldering it. Otherwise you will not get all the pins lined up.
By the way, I'm running AT853 mics (powered from a 9V battery).
Richard