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Single Ended Integrated Amplifier

After a few years in production NAT revised (from April 2019) a real high-end integrated amplifier from Single to Single HPS (Hybrid Power Supply)!

Single HPS operates in single-ended, zero global feedback, pure class A manner. Power output is set to 50W into 8 ohms. Best quality of amplification will be with moderate sensitivity loudspeaker with stable impedance from 4 ohms to 16 ohms.

Driver stage in Single HPS form E88CC (or equivalent) tube, capable to act as low distortion stage, made by military standard, indicate as N.O.S. (new old stock) grade of the highest quality.

Output stage form military grade direct heated triode (D.H.T.) GM70, high performance tube capable to dissipate up to 125W. Single HPS represent a truly single-ended design without parallel connection of  tubes with high 50W of power output.

Hand coiled and assembled wide bandwidth output transformer (custom designed for NAT ) is used.

Single HP's bandwidth from 10Hz – 60.000Hz has exceptional good flatness for single-ended zero feedback type.

By specific connection of the output transformer with power tube, amplifier may drive almost any type of loudspeaker with dumping factor that is few times higher than in standard.

Filament soft start  improve reliability of entire integrated amplifier by avoiding voltage stress during turn-on procedure. Standby function additionally improve reliability of non analog section.

No any adjustment from time to time of output tubes is necessary. Single HPS has automatically adjust current capability for GM70 tube no matter of tube duration – constant current in time domain –  from the brand new to the end point of tube lifespan.

To avoid unnecessary heat Single HPS has possibility to be selected to low mode - 25W of output power with significantly reducing of power consumption!

Power supply section participate in sound quality almost as amplifiers main circuit. Silent power unit of 400W is designed for double power than Single HPS consume.

Over 500J of energy storage is used in form of high quality multi-capacitors bank!

Separate power supply (conditioner) unit additionally improve sound quality by removing magnetic leakage flux inside the main chassis!

For the highest "purity" of power supply voltage a special designed and selected passive components are used. Tonal quality is totally independent from line voltage instability. 

Attenuation network as one of the most important part of any integrated amplifier is realized in Single HPS as 56 high reliability silver contact silent relays network. Only one resistor of high quality at any volume setting is on the signal path (shunt type) ! Volume control linearity is at high level - from DC to over 1MHz!

Single HPS is equipped with multi function remote control unit made from solid block of aluminium. Front panel is made from solid block of aluminium as well! Indication of all amplifiers function is shown by blue led's on universal function display.

Quality of electronic components that is used inside Single HPS are at high level - military grade and N.O.S. tubes, Teflon and "in-oil" military grade capacitors, Caddock and Vishay 0.1% resistors, many electrolytic capacitors for 105C of operating temperature, last generation J-FET semiconductors, Schutzinger laboratory grade connectors, Hammond mechanics, silver-ofc input wiring…

Single HPS works properly at world wide AC line voltage from 100 – 250 VAC, 50-60Hz (different voltages set in factory only).

NOTE:
          -Standard version use pseudo-balanced input
          -First step of upgrade : pure-balanced input realised with hand coiled nano-crystalline core transformer
          -Premium step of upgrade : pure-balanced input realised with hand coiled silver-ofc wired nano-crystalline core transformer

Technical Specification
Name Value
Type Single Ended Tube Base Zero Global Feedback
Power Up to 50 W @ 8 ohms
Frequency Response 10 to 60 kHz, -3 dB; 20Hz to 20kHz, +/-0,5dB
Noise 90 dB IHF  reference to 1W
Sensitivity & Gain 0.4V for full power, 34 dB (X 50)
THD & N < 0.15 % @ 5W output, < 1 % @ 40W output < 5 % @ 52W output
Input Impedance >15 kohms
Output Impedance <0.8 ohms (damping factor >10 reference to 8ohms load @ zero global feedback)
Stereo Separation >95 dB
Tube Complement 2 x 6N23P (E88CC) & 2 x GM70  per unit
Power Requirements 100VAC to 240VAC (50 to 60 Hz), max. 390 VA
Dimensions 19" (483 mm) wide ´ 15.7" (400 mm) deep ´ 10.2" (260 mm) high
NETWeight (Control Unit) approx. 100 lbs (45 kg) unpacked
TOTAL Weight approx. 120 lbs ( 54kg) packed in polypropylene crate

 

Design Features

- single-ended type - integrated amplifier
- zero global feedback design
- triode direct-heated (D.H.T.) output type
- short signal path
- full dual mono construction
- 50W of pure class A
- output section - GM70 tube by military grade and N.O.S.
- driver section - 6N23P (E88CC) tubes by military grade and N.O.S.
- hand coiled balanced output transformer (custom designed for NAT)
- separate transformer-conditioner power supply unit
- regulated power supply for all stages (including the output)
- universal (12 leds) display
- filament soft start operate to improve entire reliability
- remote control made from solid block of aluminum
- automatic bias current control with long term stability
- standby function
- relay (silent type) attenuation network
- hand assembled all modulated chassis
- high mass Schutzinger laboratory grade output connectors
- gold plated PTFE insulated RCA input connector custom ordered from NAT
- extensively used computer numeric control machines (CNC)
- 5/8" (15mm) thick aluminium front panel
- cover cage (optional)
  

Specifications are subject of change without notice