Did the op amp Mod on my triaxis

[Paul Secondino]

Switched out IC3 for a burr browns ( now Texas Instruments) 2604 . I am certain I am hearing some more midrange compared to stock and the dynamic response is improved I'd say about 15 to 20 percent. It isn't like the triaxis is transformed into something else but the response is nice and I'd say that after about 40 or 45 minutes, the op amp sort of breaks in a bit.

I have a question however. My tech accidentally removed the op amp at IC1. So since that happened , we used a Burr browns OPA 2134 to replace it. I'd like to know if there is any kind of compatibility issue in this case ?

Also, I'm having a problem with the presence on the triaxis fading out and back in repeatedly. The sound gets a bit dark and then comes back and then goes again.This jsut began today after the op amp swap. I am not certain it is the op amp causing this as I jsut had the same exact problem with one of my mark 3's and Mike B found a bad cap in the presence feedback circuit.

All feedback appreciated .Thanks

 

[leadfootdriver]

Sorry you're having problems. All' the schematics and mod notes are on tube freak.com
http://tubefreak.com/schema.htm#triaxis Maybe the IC1 is in the presence circuit?.

Maybe it is something dumb like a capacitor. My 2:90 blew up recently because of a $2 electrolydic filter cap. Mine (caps) lasted 8 years. sometimes they last 30... What a mess that job was.