Trilogy 903 Preamplifier

The 903 is Trilogy's single-ended valve preamplifier, in the range since 2016, and the partner to the 993 power amplifier. The gain stage uses the 6H6П super tube for all voltage gain. This Russian military triode has high transconductance and low mu for performance at audio frequencies, and the grounded grid configuration allows it to operate in pure Class A with the highest linearity and lowest distortion. Output impedance is low for drive capability.

Three transformers feed the power supplies. The valve's high voltage supply is actively shunt regulated, so the regulator can sink as well as source current — the detail that keeps the voltage rail quiet and stable under all conditions. Six pairs of RCA inputs feed two pairs of RCA main outputs plus a tape send. Control is through the rotary encoder with enter and escape buttons: display brightness, custom input labels, per-input gain trims, film mode, security bonding, sleep countdown, timed system switch-on over TASlink and remote operation.

The optional integral phono stage is not an afterthought. It has much in common with the 907, being a Class A design with passive RIAA equalisation and a fully discrete active circuit, and its on-board shunt regulators have their own power supply. Gain for moving magnet or moving coil, and cartridge resistance and capacitance loading, are all adjustable from the menu hierarchy — locally, by infrared handset, or over TASlink.

• Topology: 6H6П super tube, grounded grid, pure Class A voltage gain
• Phono stage: optional integral MM/MC; Class A, passive RIAA EQ, fully discrete; gain and loading adjustable from the menu
• Inputs: 6 pairs RCA phono sockets; 50 kohms
• Outputs: 2 pairs RCA main (under 200 ohms); 1 pair RCA send (tape)
• Gain: 14 dB +/- 0.5 dB inputs to main; 0 dB inputs to send; film mode 0 dB +/- 1 dB
• Frequency response: 2 Hz – 50 kHz +/- 0.5 dB
• Distortion: less than 0.05% A weighted at 1 V output
• Phase: phase correct (non inverting)
• Power consumption: 40 W maximum
• Dimensions / weight: 465 x 312 x 106 mm (465 x 350 x 106 mm including connectors) / 10 kg