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Hi. Just bought this one on ebay. It looks like really nice preamps with tranformers on the input and one tranformer on the output.
What i'm thinking to do (after reading the schematics):- swap quad opamps on the signal path with modern and faster ones like LME49740 or LT1359 (will add 0,1uf psu bypasses as well);
- upgrade psu smoothing caps to 2200uf and add a parallel 0,1uf bypass;
- upgrade all EL caps on the signal path to at least 47uf/25v Panasonic FM's;
- change the output voltage on the LM317 regulator from 30v to 34v, or 36v if i use the LT's instead of the LME's (more juice to the opamps and phantom power);
- adding unbalanced outs from each preamp.
What you guys think of the circuit and the mods i'm planning to do?
What opamps are in the box now?