Op-amp replacement for Unison Unico

Thanks for packaging info in opamps.....
I'd never even thought to check, thought Surface mount stuff makes sense.

The are available in single channel, too, right?

check the CMOY DIY pages for a big list of tested opamps and listening impressions.

I upgraded the NJ4556a (2-channel)op-amp in my phono preamp to 2 opa627's (mono) on a Browndog adapter recently. Result was lower noise and greater clarity. So much more clarity that I ended up hearing how much the coupling caps affected the overall sound, but that's another story.
OPA627 is available in 3 different packages, DIP which can be plugged into a socket or soldered through hole, TO-99, which is round and soldered through hole, and SOIC, which is surface mounted and what you would use on a Browndog adapter. Soldering those 2 SOIC's to the Browndog was a little tricky (most spiders I've seen are bigger than SOIC) and required a fine point soldering iron and a breadboard to hold things still. I had a little noise when the browndog assembly was plugged into a standard DIP8 socket I attributed to contact noise, so I would recommend either soldering the assembly right to the board (after carefully cleaning and shining all contacting surfaces) or using a gold plated socket.
Another mono amp I tried on a Browndog was OPA827, which was cheaper and sounded similar to the 627.
I tried OPA2134 which I liked more than NJ4556a but it was too noisy for the amount of gain I needed.
Like Magfan suggested, you're going to need to pore over the data sheets before you jump in.
I'm not sure what package is best with regard to heat dissipation for your situation. The SOIC's on the Browndog get real hot to the touch, but so far have been working fine.

If this is a 'dual' opamp....8 pin dip of standard configuration, there are dozens of opamps from which to choose.
I built a headphone amp using OPA2134s.
And yes, several 'models' of each can be produced. some have parameters optimized which won't mean much to an audio guy.
Learn to read the data sheet........at least for the stuff parameters you need.

Thanks Viridian and Drrsutliff. I am going to open up my amp tonight to take a look. I have also noted that there are a number of variations of the OPA-627 which I will reseaarch a bit more. I plan to tube roll also but I noted that in the 6 moons review of the level 2 mod of the Unico that the reviewer attributed much of the improvement in dynamic drive and frequency extention as likely due to the replacement of the op-amp to the Burr-Brown's. So I thought that if this was a plug and play operation, that I might get some appreciable improvement by doing this myself.

It also depends, as Viridian alluded to, what opamp you are replacing. If the stock opamps are 2 channel then it will take two of the 627 (mono opamps) on a brown dog adaptor to do the substitution. Also you need to note the direction of the chip you removed (look for a small indentation on one end) and make a note. Make sure to ground yourself to the unit to prevent static discharge. Radio Shack has an inexpensive strap for your wrist. Sounds much worse than it is. This is something you can do.