NAT audio - Innovative Audio Manufacture

Switch to desktop


Direct Coupling Dual Mono Vacuum Tube Line Stage
-With Remote Control-


Utopia Direct Coupling Dual Mono Vacuum Tube Remote Controlled Line Stage represents top of the Line Stage segment in NAT audio equipment. NAT is really proud to present line stage with no coupling capacitors or inter-stage transformer on signal path, yet zero feedback concept. Sound is treated only with vacuum tubes and hi quality small value resistors.

Utopia is a vacuum tube dual chassis line stage preamplifier in full dual mono configuration. First chassis called Control Unit contain power supply, digital controls and all other modules. Line Stage is second chassis, which contain only analog circuits.

LINE STAGE CIRCUIT: Unique all triode zero feedback configuration makes this low output impedance preamplifier capable to drive any kind of power amplifier. Long life military grade tubes 6N23P-EV (E88CC equivalent) & 6N6P/6N30P-DR special low impedance triode are used in line stage circuit.

Volume control is realized with 16 high reliability relays. Contact material of these relays is silver with gold glad. By relays switching combination volume control can be adjusted in 100 steps.

ANALOG POWER SUPPLY started with two custom-made low-density toroidal transformers. All needed voltages are regulated with 11 stages per channel(22 stages in total). Anode voltages are double regulated for each analog stage.

Control Unit Chassis contain two high quality input AC filters one for analog power supply transformers and one for the digital supply.

Micro-controller Based DIGITAL CONTROL CIRCUIT controls all necessary functions of preamplifier, and its current status is displayed on an alphanumerical front panel. Front panel is made of twelve dot matrix displays. Digital Control Circuit is supplied with custom-made low-density toroidal transformer (totally three transformers per unit). Remote control unit made from two pieces of solid block aluminum controls all preamplifier functions.


Technical Specification
Name Value
Frequency Response DC to 500 kHz, -3 dB; 20Hz to 20kHz, +/-0.00dB @ 47 kohms
Noise 90 dB IHF ref. to 1 Vrms output
Gain 15 dB(x5.6) Phase status: invert (180 degree)
THD & N < 0.1 %
Input Impedance > 27 kohms
Stereo Separation > 95 dB @ 1 kHz
Tube Complement 4 x 6N23P-EV, 2 x 6N6P/6N30P-DR; all military grade
Output Impedance < 80 ohms @ DC to 500 kHz
Power Requirements 110 VAC or 220 VAC @ 50 to 60 Hz, max. 80 VA
Dimensions (Control Unit) 19" (483 mm) wide x 10.4" (265 mm) deep x 5.5" (140 mm) high
Dimensions (Line Stage) 19" (483 mm) wide x 10.4" (265 mm) deep x 4.3" (110 mm) high
NET Weight (Control Unit) approx. 24 lbs. (11 kg) unpacked
NET Weight (Line Stage) approx. 17.6 lbs. (8 kg) unpacked
TOTAL Weight approx. 55 lbs. (29 kg) packed in wooden box


Design Features

- full dual mono construction
- direct coupled preamplifier (no coupling capacitor or inter-stage transformer)
- zero feedback (unique construction)
- all triode configuration
- dual chassis concept
- sophisticated attenuator construction realized with relay network (no electronic switch)
- high current 6N6P/6N30P-DR triode output tube (military grade)
- VISHAYâ„¢ metal foil 4ppm input resistors
- line stage and analog circuits are powered by low density toroidal power transformer (one for each channel)
- separate low density toroidal power transformer are used for digital control circuit
- stand by mode with tube pre-heated function
- soft start operate
- gold-plated teflon insulated connectors
- hand assembled aluminum modulated chassis
- extensively used computer numeric control machines (CNC)
- engraved 1/2" thick aluminum front panel
- standby mode
- full dot matrix display
- remote control made from two separate solid blocks of aluminum

Specifications are subject of change without notice

Copyright © Nat Audio, Serbia | Developed by

Top Desktop version