Operation
With tube rectification, the high voltage ramps up slowly.
The power switch is a 2-position switch.
Up position is power ‘OFF’.
Flip the power switch Down to turn ‘ON’.
The green LED lights.
The preamplifier will power up in about 15 seconds.
When making or breaking any connections, always turn off
the power to the amplifier first, so that no hum or transients
are transferred to the speakers.
When sitting down to a listening session, it is a good idea to
let the system warm up for a half-hour. This stabilizes the
circuitry, and makes it sound better.
Description
The Phono tube preamplifier is a dedicated preamplifier for
LP record replay.
It accepts an input from a high output Moving Coil or Moving
Magnet cartridge. The correct loading is applied for the type
of cartridge used, and can be customized for a specific
cartridge. For low output moving coil cartridges, input
transformers can be installed.
The overall design is simple and direct. Passive RIAA
equalization is applied between two active gain stages. These
are high gain stages using low noise Russian 6N2P tubes. A
subsequent buffer stage using the Russian 6N6P tube
provides high current drive and a low output impedance.
The gain stage tubes can be substituted by the ECC83 series
of tubes. A switch provides for the change in heater wiring for
these tubes.
All wiring is point-to-point. All gain stages operate in Class A
mode. No global feedback is used.
The power supply has separate EI-Core transformers, for the
heater supply to the tubes, and for the high voltage supply to
the various stages. Each stage of the high voltage supply is
independently filtered through chokes and RC filters. A tube
rectifier is used.
The Phono tube preamplifier is housed in a naturally finished
solid sheesham cabinet.
