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bisszerk 25th February 2011 03:46 AM

Help upgrading opamps!
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I'm Brandon,

I have a M-audio projectmix i/o 8 channel mixer (M-AUDIO - ProjectMix I/O - Control Surface with Motorized Faders and 18 x 14 Audio Interface). I have recently taken it apart to see if there are any mods I can do. I found that there are 8x JRC5532 opamps on the XLRs inputs. These I want to replace first. There are JRC4580 opamps on the TRS inputs and 4 JRC4580 opamps on the 4 main speaker outputs. Money being no option for this project, I am looking to replace all opamps with the BEST opamps as far as specs go... highest frequecsy response 20hz-20khz and so forth. I am not an engineer by any means but am very handy with a soldering iron and can follow schematics decently. This mixer cost me $1200, so I just want a drop in chip. I do not want to have to change the circuit at all. However, I will also be replacing the caps with top end caps-I can easily look at the specs on those so.. do not need help with that. I do not have schematics for the Projectmix, but can provide some photos inside. Any one who can help my e-mail is

linuxguru 25th February 2011 09:15 AM

You may want to post your query at the Analog Line-Level forum - there may be more interest there.

Regarding op-amps, there is no such thing as a universal 'best' op-amp - different opamps are good at different things. For input line-level buffering, filtering, etc. you can take a look at the NatSemi LME49720 or similar. For output signal buffering and headphone drivers, you can take a look at the THS4032 (SMD only) or LM6172 (DIP and SMD).

abraxalito 25th February 2011 09:29 AM

Is there something wrong with the sound of your mixer that makes you want to roll opamps? All opamps pretty much have the same frequency response 20-20kHz. There's nothing much wrong with the NE5532 provided its treated well (input filtering, power supplies and decoupling) and as you don't want to make circuit changes there will be pretty much no chance of improving the overall sound from changing these opamps. Swapping them out might well make some aspects better but others worse, depending on the particular design.

bisszerk 25th February 2011 09:31 AM

Thanks for the response. I am generally looking to get the best sound quality as possible. I know there is no perfect or best answer, but I know I could get better sound by modding this unit. A days worth of research has put me looking into OPA1612, OPA2604, or OPA2134. Are the ic's you mentioned direct drop ins? Are they comparable to the opas? Would there be any harm in just putting random chips in to test, as long as the pin-outs match (and of course the voltages and etc.)? Just want to push the unit to its limits.

bisszerk 25th February 2011 09:35 AM

The unit sounds good, but not shiny on the top end. Somewhat dull. After reading about the Black Lion Mods for this unit (that are now discontinued), I figured why couldn't I operate a bit and get a better sound out of this thing. Obviously, there is more to the sound than the opamps, but I was under the impression that this would be a cheap but effective upgrade.

AndrewT 25th February 2011 12:29 PM

I fully agree with Abrax.
It might be cheap to swap opamps. It is likely to take many weeks of circuit board modifications just to get performance back to where you were. It could take many more weeks of experimentation to actually improve the performance. In the meantime you have used dozens of cheap components that are now binned and you have probably lifted at least a couple of traces and implemented botched repairs just to get some sound out of your heavily modified gear.

Simply swapping one opamp for another proves only you are gullible to audiofools' suggestions.

Taking a piece of gear that has been optimised for the opamps the designer selected is virtually guaranteed to perform less well with 90% of the alternative opamps you might select as possible. If you are really lucky the other 9% will make the performance the same. Finding the 1% that improve the performance without optimising the gear to suit that "perfect" replacement is not an easy nor cheap modification.

bisszerk 25th February 2011 07:06 PM

Thanks guys,

As the circuit looks somewhat simple, it seemed like a good idea to experiment with. Along the way maybe I would learn something. But before I decided to dive in and BLOW something up I wanted some suggestions. So... being that I don't have schematics, only photos, is there any suggestions to the circuit that might improve sound quality. I am willing to do slight changes, just not a complete overhaul as I am not experienced enough. The section that I photographed is the complete amp circuit for all channels on the board. The other pcbs are the power supply, faders, ad/da. Looks like that is all. So changing to high quality caps like Elnas or Black Gate, and different preamps wouldn't make much of a difference? The only other thing is resistors and I can't see where they would matter.

MJL21193 25th February 2011 07:13 PM


Originally Posted by bisszerk (Post 2482879)
Thanks guys,

As the circuit looks somewhat simple, it seemed like a good idea to experiment with. Along the way maybe I would learn something.

Doubtful, you are already ignoring the extremely solid advice you are getting.
Want to learn something? Build a 'simple' (your word) circuit like the one you are trying to 'improve'. You'll learn plenty...

Mooly 25th February 2011 08:14 PM

All that has been said is correct... and I have said the same in the too so don't want to sound hypocritical suggesting otherwise...

however, I would say that if you want to experiment then do so. Many on here know I like the OPA2604, and that would be my choice I think to replace all. The LM4562 is the successor to the 5532 but one I haven't tried as yet. Of all the opamps I have used the 2604 is the most "coloured" but to me it's also the most musical. So try it!

Assuming single sided print why not fit sockets and try several. Even the ancient TL072 can sound darned good over the 5532 in many applications as long as the application is within the more limited drive capability of the TL072.

Second time today I have posted this, but this is what is meant by optimising a simple circuit in detail,
post#1017 onward,

bisszerk 25th February 2011 08:30 PM

Sorry guys, not trying to ignore great advice, but I am definitely a hard head. As long as I can test things out, I will. It's in my nature. My way of learning is to disassemble and tamper (Hands on). For me to fully understand the effects, I must hear or try it myself to make my own conclusions. That being said I was definitely going to use a socket so that I will only have to solder once. I will likely test a few ics, since I already have some samples coming (OPA1612, OPA1642.) I am definitely looking for something that is a little more colored (musical). Mooly, you kinda hit the nail for me. I was looking for this type of answer. So now I know I could theoretically replace all the ics with the OPA2604 and no harm is done, cool! Love the help folks, exactly why I joined diyaudio!

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