The phono only LCR preamp (no linestage) uses 6688, 6688 and 6E6P tubes.
These tubes were designed and built towards the end of the tube era, and are perfect devices for audio preamplifiers.
The LCR Cortese is suitable for any moving coil cartridge, but not moving magnet.
Impedance switching allows for loading of 10,100,1000 and 47,000 ohms (or whatever values are required.
To ensure enough gain with even the lowest voltage MC cartridges (0.1mV) the phono section has nearly 80dB of gain - that's an enormous amount of gain and its a real task to ensure quiet operation with no hum and hiss below the vinyl floor level.
The input stage of the phono uses a cascode circuit with J-fet and 6688 (E180F) tubes.
With nearly 30 years of development this cascode circuit negates the need for a passive step up transformer and has all the advantages of active operation- greater dynamic range , more linear frequency response and suitability for all MC cartridges.
To ensure it is quiet , a special earthing arrangement is needed, along with extremely quiet power supplies - more on that later.
The next stage (6H23 tube) is another gain stage with transformer output, which provides the low impedance and drive necessary to drive the L coils for the RIAA equalisation.
These are specially built by Lundahl and are finest quality. They are precisely measured and the required CR values are matched within very fine tolerances.
The last stage (6H23 tube) provides some more gain and the drive needed to couple with the line stage.
Polyprop caps are used throughout, but kept to a minimum.
In line with Supratek design goals, electrolytic capacitors are only used when absolutely necessary - there are only 2 in the phono stage, and none in the linestage.
Compare this to a typical phono preamp which can have dozens of strident sounding electrolytic caps.
The line-stage is another multi- year development that is designed to be as transparent as possible , in order for the astounding sound of the LCR circuit to come through unaltered and rich in dynamics.
It has extremely low output impedance and will drive any, and multiple power amps.
I've also concentrated on making both the phono and linestage as robust and reliable as they can possibly be.
They only use design circuits and components that will have an almost indefinite lifetime - I'm sure that like other Supratek products it will become a classic that will be performing flawlessly and at the highest level many years from now.
The heart and soul of any audio electronic component is the power supply, and the PSU for the LCR phono preamp is an example of clever and uncompromising engineering focused on sound quality and robustness.
The tube shunt regulated supply for the high voltages is responsible for the Supratek sound- precise imaging and sound-staging , and rock solid stability .
Seperate heater supplies for both phono stage and line-stage ensure super quiet noise levels, even with 80dB of phono gain .
The Supratek LCR phono is the only MC cartridge capable LCR tube preamp in the world.
