Replacing IC opamps with DOAs (Yamaha M512)

[gnsdg]

Just picked up an M512 for cheap after talking through some EQ mod options on the "Drawing Table."  (Thanks, again!)

I'd like to replace just a few of the TA7322s with discrete opamps, and I definitely have some questions.

Voltage supply is an issue, but I feel comfortable dealing w/ that.  I'll have to build 9-pin to 2520-style pinout converters, so I can always build regulators into them if need be. 

Focusing on just replacing a channel head amp, here's what I KNOW I don't know:
- what pieces of the circuitry surrounding the TA7322 (http://89.228.128.119/RemoteDownloader/files/20130130/31815a538f949b2962b6956e0d6cf759/M512YAMAHAServiceManual-EN.pdf) are unnecessary/should be removed if I'm going to use, let's say, a 990?
- how do I deal with the connections for, let's say, phase compensation, that many ICs have but DOAs don't? 

For the record, I'm not doing this because I think the 7322s are awful--I'm just interested to try out some DOA-based pres, and this is cheaper than building a bunch of 51x stuff.  I'm good with small stuff.

 

[abechap024]

Just try it. if it oscillates put a bigger capacitor in series with the feedback resistor. (by bigger i mean like 47pf)

 

[gnsdg]

Ha ha, I like your attitude!

OK, so... the connection in the circuit that was going to pin 4 of the 7322 goes where?  Pin 5 connection goes to -V on DOA, pin 8 goes to ground on DOA (?), and pin 9 goes to +V?

 

[gnsdg]

Forgive the bit of a bump, but I'm thinking after having thought about it a bit more that I'd just connect the DOA's +V and -V connections directly to the respective voltage supplies, and pretty much ignore the surrounding circuitry that went with the 7322.  I assume phase compensation is irrelevant as well, so it's just a matter of connecting the + and - inputs and output as well.

Ground is ground?  There's no floating ground here is there?

 

[nickvivid]

Resurrecting an old thread I know. This has answers, not questions I assure you. I figured it made more sense to add to a topic people were searching.

I spent a lot of time figuring out a replacement for the 7322p chips in the m512. (This should work in the 508 as well and possibly other mixers, read on)

TI5534 replaces the TA7322p without a problem in this mixer. There's better mids, smoother high end, better transients, and overall tonal presence is improved. It removes the grit almost completely as well as fixing a lot of that pillowy/cloudy midrange.

The main problem is this board has the 7322p on 24v rails and those are going to fry the 5534s. Luckily, there's 16v rails attached to the EQ 4558 opamp, and we can use those instead, since the 5534 is optimal around +/- 16v

7322p -> 5534

2->3
3->2
7->6

I usually take a 5534 chip and clip off legs 1, 5, and 8. I straighten the legs out, except for pin 4, which i bend around the back, flip the chip over, and insert pins 2 and 3 into the board opposite configuration so pin 2 goes to 3, and 3 goes to 2. I then run a wire from pin 6 on the 5534 chip to the pin 7 line on the board (i usually just solder it to the end of the resistor that's in line with pin 7 on the board).

I then search out the 16v rails, and connect pin 4 of the 5534 to pin 4 of the 4558 midrange opamp (-16v rail), and pin 7 on the 5534 to pin 8 of the 4558 (+16v rail). Add .1uf decoupling caps to + and - of each chip (leg attached to chip as short as possible. Leg to ground as long as needed). I've read the 5532 replacement for the 4558 makes the EQ control smoother in these as well, though I haven't done that yet. When powering on, there's a little oscillation, probably as to do with the timing of the 16v rail being powered, so i keep the volume down when turning it on.. But i haven't noticed any other issues as of yet. All sounds good to me.

Nick