This application will produce a moving magnet and high output moving coil cartridge compatible Phono stage. It use two Universal Tube Output Stages together with a LCR 600 ohm module to form the RIAA Equalisation network as Phonostage. One UTS Module will be used for each channel, so Tubes used should be identical in manufacturing and preferably matched.
The resulting Phono Stage will offer 47kOhm input impedance and around 38db Gain in MM mode. Gain with the Cinemag MC stepup transformers will be 62/68db with a load of 140/36ohms.
Our implementation produces the most accurate RIAA EQ we have ever seen from an LCR type phono stage:
We include military specification polystyrene caps with the kit to meet these specs. Such adherence to RIAA standard results in very quiet playback that minimizes grove noise and diminishes the presence of tics and pops.
3.1 Jumper Settings
Please note that Capacitor C109 is (intentionally) not fitted. It is not used and should be left off the PCB. The connection pad on the PCB near the upper end of the PCB (as above) is used to take off the signal feeding the LCR RIAA.
3.2 Input/Output Wiring Diagram MM Only
Please note that the Mute and Mono Switches may be safely omitted. If the mono Switch is omitted the four 33 Ohm Resistors also can be removed.
In most Phono Stages using LCR RIAA Equalization the LCR RIAA Module is coupled using either capacitors or transformers. In our circuit no such coupling device is needed.
The LCR RIAA Module is coupled directly to the output of the input gain stage using only a single Tantalum resistor to present the correct impedance to the LCR RIAA module.
In order to allow this direct coupled circuit, the wire feeding the LCR EQ Module via the 680 Ohm resistor is soldered on the PCB to the connection for the omitted C109, nearest to the edge of the PCB that contains the audio connections.