ive been working on a design for 24 preamps as a front end for a new 24io interface I'm soon to get. It consists of: -12 API 312 pre's -12 Jensen pre's (with JT-16-B input trans.) (API 2520 OpAmp) (JT 990-C OpAmp) I'm thinking of mix-matching the OpAmps with the Preamp "sockets"... That would make the front end have 4 completely different circuits (and hopefully characteristic sounds) to choose from. Like 6 312's with 2520, 6 312's with 990, 6 Jensens with 2520, and 6 Jensens with 990. Does this sound alright? I realize I'll need to knock down the supply voltage from +/-24 to +/-20 to power the 2520's but other than that... I guess the only concerns I have are input impedance for the swapped Pre's as the OpAmps indubitably interact with the mic impedance, and signal distortion at the OpAmp inputs if one chip is rated for a lower input signal than another.....? And so the question: Is this swap safe and sound? If not, what modifications should be made to make it so? I've been staring at schematics and laying out PCB designs for the past week and I'm now about to pull out all my hair and set it on fire and dance on it as I howl at the moon. :shock: Cheers.