I built this phono preamp to listen to vinyl on my system (duh). It's based around ESP's multi-stage active/passive RIAA equalization scheme. I designed a toroidal transformer, regulated power supply. I based the layout around 4 single channel opamps, as this gives the greatest versatility for switching op-amps. Originally I had OPA134's installed in all four locations, however the LED power wire moved during testing and shorted to the incoming 120VAC power line, and blew a lot of stuff up, including the chips. The only other single channel op-amps I had were LM741's (I already slapped myself, don't worry), and CA3140's in the old school round metal cases, and used two of each in the meantime. Today I got 4 OPA228's and put them in. These are now pretty much my favourite op-amps ever. While proper implamentation makes much more of a difference than the opamps themselves, these are just fantastic chips. The sound isn't warm and tubey, or cold and analytical, it's clean, it's present and it's awesome.
This of course is the inside. I don't mind vera board for one-off projects like this.
The back, input/output through RCA jacks. These are insulated from the chassis ground, to ensure the prevention of ground loops. The switch on the rear panel is a ground lift switch. It's useful for different grounding scenarios, where being able to disconnect the mains ground becomes exceptionally useful to minimize hum. The ground connection is an insulated banana plug connector.
Professional 2U high panel front, for eventual rack mounting. Minamilist styling, with an LED rocker switch in the middle of the front panel. All in powder coated black. Anyway, thought you guys might like to see.
