Topic: Self-hacking for UA5 (OPA2134 opamp?)

[poorlyconditioned]

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

[Busman Audio]

I am in the process of doing this exact swap. I have the ICs and now just need to find the time to do the work. The ICs that are in my UA5 are 4570s and the install is a simple swap. These are a much better op amp than what is in the unit. Should provide less noise and tighter punchier bass. I will be posting results when I am done. I will also be changing a bunch of the capacitors in the near future.

[Chuck]

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?

[poorlyconditioned]

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

[poorlyconditioned]

I am in the process of doing this exact swap. I have the ICs and now just need to find the time to do the work. The ICs that are in my UA5 are 4570s and the install is a simple swap. These are a much better op amp than what is in the unit. Should provide less noise and tighter punchier bass. I will be posting results when I am done. I will also be changing a bunch of the capacitors in the near future.

Dear Bussman,

Hmm.  I just looked at the specs.  I'm not sure that the OPA134 is much better than the 4570 after all.  The 4570 seems to have less noise, but the the OPA seems to (?) have less distortion.  By the way I put both spec sheets on my webpage.  I put up the 4570 since I had to search a bit to find it.  Anyway, here they are:
  www.cs.uwaterloo.ca/~mannr/uPC4570.pdf
  www.cs.uwaterloo.ca/~mannr/OPA134.pdf

  Richard

[shaggy]

FYI,

Even the Oade W-modified has noise issues when the rear line-in gain pot is turned up. (starts around 3 o'clock on the dial).

ANDY

[twatts (pants are so over-rated...)]

FYI,

Even the Oade W-modified has noise issues when the rear line-in gain pot is turned up. (starts around 3 o'clock on the dial).

ANDY

I'm guessing the PLus Mod fixes that...  Improves RCA inputs, Phantom, and DC power...

T

[Daryan]

Start with the op amps, and I mean all of them, then move onto trhe capicitors, changing out the crap caps for much better, higher rated value caps...panasonic caps usually work.  I will take a look at the guts of the thing from the pictures and see what I come up with when I get home.

D

[Busman Audio]

the caps in the unit are Panasonic already. You need to change them to film caps to make it worth it.

[Daryan]

What are the values of the caps in there at the moment?

[Chuck]

What are the values of the caps in there at the moment?

The DC blocking caps in pre-amps are usually 100mf 50v.

[BobW]

Analog Devices, but the good stuff ain't cheap.
Or all that easy.
Good luck, and e-mail me if you get something worked out.

BTW, hotglue gun is the faster way to tack the SMDs before soldering.

[sickrick43]

BTW, hotglue gun is the faster way to tack the SMDs before soldering.

And MUCH EASIER to clean up than epoxy if you need to remove the SMD again...

Epoxy?  That's a permanant solution...

Rick