Single Ended Integrated Amplifier

For the first time NAT try to introduce real high-end component with a price region of entry level devices. The NAT “Single” is tube based integrated pure dual mono amplifier.

With tube point integrated amplifier, there is no need for interconnect cable between preamplifier and power section – one of the positive aspect from integrated amplifier as a single unit.

“Single” operates in single ended, zero feedback, pure class A manner. Power output is 50W into 8 ohms. Recommendation for the best result is to have medium to flat loudspeakers impedance curve, from 4 ohms to 16 ohms.

Driver (input) stage contains special tubes (triode) capable to act as low distortion voltage amplification devices.

Output stage form single direct-heated triode type 805, high performance device capable to give peak dissipation of 125W .It is a truly single ended design without parallel connection of  tubes, yet moderate 50W of output power.

Hand crafted wide bandwidth output transformer (custom designed for NAT ) is used in this unit.

Output transformer bandwidth is from 10Hz – 60.000Hz. That is extremly good result for integrated single-ended amplifier, yet zero feedback design.

By specific technical approach output transformer in combination with power tube type 805 may drive easy any type of  standard loudspeaker with damping factor that is very good for mention single-ended operation.

Soft start  improving reliability of entire integrated amplifier by avoiding voltage stress during turn-on procedure. Standby function additionally improving mention reliability, keep all amplifiers internal voltage at minimum.

There is no need for any adjustment from time to time of output tubes standing current. Electronic circuit automatically adjust current through 805 tube no matter of tube duration – means constant current in time domain –  from the brand new to the end point of tube life.

To avoid unnecessary heat from pure high class A operation, ”Single” has possibility by adaptive bias (select on front panel) to choose lower mode – 15W of output power with reducing power consumption significantly.

Power supply section also speak for itself. Main 1.000w transformers (separate wound for each channel) are custom designed for NAT “Single” also works silently. Second toroidal type transformer supply separate digital control circuits! For the purity of power supply voltage there is a special designed separate regulators also in zero feedback manner for all amplifier stages including the output one. On such a way sound quality is totally independent from line voltage instability. Tubes (input triode drivers) are by N.O.S. (new old stock) grade and have high reliability. “Single” is equipped with multi function remote control unit made from solid block of aluminum. Front panel is made from solid block of aluminum, indicate all amplifiers function with  DOT – MATRIX 6 segment display that may adjust by 15 different intensity level also with light-off mode.

Attenuation is based on relay (with gold plated contacts and silent operation) network that is computer controlled – there is 100 position of  attenuation and always is only one (single) high quality resistor on signal path.

Quality of electronic material that is used inside “Single” 0.1% Vishay resistors, electrolytic capacitors for 105C of working temperature, last generation of industrial grade semiconductors, Teflon insulated connectors, special designed power transformer, N.O.S. input tubes, high reliability silent relays with gold plated contacts…

Amplifier works properly at all world wide AC line voltage from 100 – 250 VAC, 50-60Hz (set in factory).


Technical Specification
Name Value
Type Single Ended Tube Zero Feedback
Power 50 W @4 or 8 ohms
Frequency Response 10 to 60 kHz, -3 dB; 20Hz to 20kHz, +/-0,2dB
Noise 90 dB IHF  reference to 1W
Gain 35 dB (X 55)   Phase status: non-inverted (0 degree)
THD & N < 0.1 %
Input Impedance >15 kohms
Output Impedance <0.8 ohms (damping factor >10 reference to 8ohms load @zero feedback)
Stereo Separation >95 dB @ 10 kHz
Tube Complement 2 ´ 6N1P-EV(VI), 2 ´ 805  per unit
Power Requirements 100VAC to 240VAC (50 to 60 Hz), max. 370 VA
Dimensions 19″ (483 mm) wide ´ 15.7″ (400 mm) deep ´ 10.2″ (260 mm) high
NETWeight (Control Unit) approx. 110 lbs (50 kg) unpacked
TOTAL Weight approx. 132 lbs ( 60kg) total with transport wooden box


Design Features

– single ended type – integrated amplifier
– zero feedback design
– triode direct-heated output type
– 50 W of pure class A
– full dual mono construction
– custom designed 1.000W encapsulated power transformer
– full stabilisation for all amplifier stages
– two tubes (NOS) for driver purposes
– separate toroidal transformer for digital control
– dot-matrix display (15 level of intensity with turn off light mode)
– remote control made from solid block of aluminium
– automatic bias
– adaptive bias (to control dissipation of the output stage)
– standby function
– relay (silent type) attenuation network
– all aluminium modulated chassis
– teflon isolated connectors

Specifications are subject of change without notice

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