SOLD Thanks for looking. I am selling my working Equal Opportunity (EO) moving magnet tube phono preamp. I “completed” this project in 2016 and it has been my main phono amp since then. “Completed” needs to be in quotes because I never got around to making an enclosure for the signal boards and they have lived on a piece of plywood. The power supply is complete in it's own enclosure.
A couple of notes for buyers unfamiliar with the design. My power supply is for 120V mains and the EO is a balanced in/balanced out design. The transformers can be rewired for 230VAC. Balanced input may mean minor rewiring your turntable to get a balanced signal from the cartridge.
You can read about the EO here and I highly recommend spending the few bucks to buy Linear Audio V7 and V8 for SY's articles about the design. In summary, it is a hybrid tube design that uses jFETs as input devices with 6DJ8 tubes doing the amplification. The design uses 2 amplification stages with a passive RIAA filter in between.
My build follows SY's design exactly using boards from JP and proto board for power supply and regulator boards. Premium components were used throughout with matched, genuine Toshiba 2SJ74 jFETs on the input. All components/circuits were matched where recommended. I will include 4 National 7DJ8 tubes (also matched), although it is worth your while to do a little tube rolling.
The power supply has 3 Triad Magnetics transformers, one each for the B+, B-, and DC heaters. Each has it's own diode bridge and reservoir caps in the supply housing, followed by voltage regulators and additional reservoir caps on the regulator board. The power supply and regulator board are connected by an umbilical cord using MIL spec 600V wire for the high voltage circuits. The old song goes, the components cost more than the asking price, which is true, but then this is DIY.
A couple of notes for buyers unfamiliar with the design. My power supply is for 120V mains and the EO is a balanced in/balanced out design. The transformers can be rewired for 230VAC. Balanced input may mean minor rewiring your turntable to get a balanced signal from the cartridge.
You can read about the EO here and I highly recommend spending the few bucks to buy Linear Audio V7 and V8 for SY's articles about the design. In summary, it is a hybrid tube design that uses jFETs as input devices with 6DJ8 tubes doing the amplification. The design uses 2 amplification stages with a passive RIAA filter in between.
My build follows SY's design exactly using boards from JP and proto board for power supply and regulator boards. Premium components were used throughout with matched, genuine Toshiba 2SJ74 jFETs on the input. All components/circuits were matched where recommended. I will include 4 National 7DJ8 tubes (also matched), although it is worth your while to do a little tube rolling.
The power supply has 3 Triad Magnetics transformers, one each for the B+, B-, and DC heaters. Each has it's own diode bridge and reservoir caps in the supply housing, followed by voltage regulators and additional reservoir caps on the regulator board. The power supply and regulator board are connected by an umbilical cord using MIL spec 600V wire for the high voltage circuits. The old song goes, the components cost more than the asking price, which is true, but then this is DIY.
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Lol, a couple extra grand in the hobby account. It looks like it sold already so congratulations!