The R50 Reference Preamplifier

"This Preamp is a real giant killer. A completely no compromise design"


R50MKII is a 20dB gain line stage pre-amplifier using improved SRPP circuit with no global negative feedback.

The capacitors used for signal coupling are the exotic US AuriCap.   All connections are point to point wiring using high purity copper hook up wire.   The circuit board acts as a support frame for the tubes and other components and actual point to point wirings are done beneath the circuit board.

The power transformer and choke are shielded from the circuit board. A special silicon steel EI type power transformer and choke with good high frequency response is used together with large Solen MKP metallized polypropylene filtering capacitor.

The two tubes used in the main circuit has been changed to the fabulous sounding 12AU7. In order to match with tube power amps, the R50MKII has been redesigned based on the top model R1.1, to use components that add very little colouration to the sound, so that the R50MKII can clearly show off the sound of the tube power amp itself.   A lot of satisfaction will then be achieved by trying out other exotic 12AU7 tubes like the Telefunken and Mullard.


Control Functions: Volume left / right, Input Select, Power On/Off
Harmonic Distorms (for 2V RMS at output):
0.05%(70Hz-7kHz 4:1)
Frequency Response:
(at -1dB) 3Hz-150kHz
Input Impedance:
100k ohms
Input Interfaces:
3 groups (RCA)
Output Interfaces:
2 groups (RCA)
Gain at 1kHz:
Negative Feedback:
Vacuum Tube:
12AU7 x 2 EZ80x1
440(L) x 320(W) x 210(H) mm

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