VAL Tube Amplifier And Preamplifier

"This tube-mono preamplifier combination, unique in Europe, is not only a feast for the eyes, but also technically on the highest high-end level. Craftsmanship in perfection - milled from solid aluminum blocks, combined with absolutely high-quality components, this system represents the maximum possible in terms of sound reference and appearance." 

The completely handcrafted ID 845 is a single-ended mono amplifier of the highest quality. Its output power is quite sufficient for most high-end applications. Its high current capacity combined with a large tolerance for the various load impedances ensures the highest fidelity when used with many loudspeakers.

Circuit description

Each stage of the circuit was designed to achieve low overall distortion not just by "overall negative feedback", but by clever circuit design. Nevertheless, "mainly negative feedback" was used to achieve a high damping factor.

The preamplifier, including the power supply, is a complete mono design.

The anode voltage stabilization and the operating voltage are tube types. Grid potentiometers with tightly selected fixed resistors for perfect control. Preamplifier uses 6SN7 WGTA USA military version tubes, 4x high-level input, 2x output (1x low for horn systems and 1x high for normal speakers).

Technical details

- peak power 2 x 32 watts

- Continuous power 2 x 28 watts at K-2+3= < 1%

- input impedance 100k Ohm

- input sensitivity 400 mV RMS for 4 watts

- input circuit 2 x SRPP (extremely low distortion) from the 1970s

- driver stages 300 B and 845 have a DC heater

- output transformers with 4, 8, and 16 ohms

- Internal resistance approx. 1 Ohm with 8 Ohm output

- Fixed adjustable grid voltage supply for 845

- Extremely low impedance (hard) power supply

- Separate high voltage and mains transformers

- Dosel shielding, operating voltage of tubes 845=900 V and 300B=400 V

- Special 50 Hz transformers

- Anti-vibration protection against high-frequency interference

- Only one film capacitor in the entire signal path

- Cerafine electrolytic capacitors in the power supply unit

- Sound-defining drivers + amplifier circuitry of the 40s

- Pulse-stable dimensioning due to small internal resistance of the individual amplifier stages

- Uncritical with complex loads  

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