Inovative Audio Manufacture

Single Ended Mono Block Power Amplifier

After a several years in production NAT revised (from November '19) a real high-end amplifier-Transmitter HPS (Hybrid Power Supply).

Transmitter HPS is a reference point power amplifier made by NAT as pure class A, single – ended type with zero global feedback circuit configuration.

Transmitter HPS gives an opportunity to listening the sound on two different mode - high power setting to 80W or low power to moderate 40W, both of pure direct heated triode type. With power of 80W in single – ended configuration there is a capability to drive wide variety type of  loudspeaker.

Philips (or equivalent) QB5/1750 type as output device represent high technology in vacuum tube manufacturing. Potential of output tube reach 565W of heat dissipation! Transmitter HPS used only 40% of max. dissipation that significantly decrease working temperature point for further reliability improvement. Construction of output tube is very robust in mechanical domain resultated in microphonics-free sound reproduction. Special designed pure non-magnetic pipe type cover cage additionally improved negative vibration feedback effect from the environment, correlate to further increase of micro detail in sound reproduction. For the audiophiles with sensitive loudspeaker Transmitter HPS offer low mode option to lower the output power to 40W that further decreased power consumption of output tube - resulting to much lower heat dissipation.

Input and driver tubes (6N6P) are made by military standard, indicated as N.O.S. (new old stock)  grade of the highest quality.

Hand coiled wide-bandwidth output transformer (custom designed for NAT ) is used in Transmitter HPS. Output transformer is constructed with no less then 52 separated wire layers. Bandwidth reach 8Hz – 110.000Hz as exceptional good flatness for single - ended zero global feedback amplifier. Output speakers connectors are realized in laboratory grade style. NOTE: Transmitter HPS may drive speakers from 4 ohms to over 16 ohms. Zero global feedback concept is the best solution for purity of sound reproduction without negative influence from wide variety of speaker impedance. 

Power supply section participate in sound quality as well as amplifiers main circuit. Silent power unit is designed for double the power then driver of Transmitter HPS consume. There is a separate voltage regulators for all amplifier stages including the output one. Tonal quality is independent from line voltage fluctation. Soft start tubes filament supply additionally improved Transmitter HPS reliability by avoiding inrush voltage stress during turn-on procedure.

No any adjustment of output tubes standing current is necessary. Automatic bias circuit adjust current through mighty QB5/1750 tube.

Quality of electronic components that is used inside Transmitter HPS are at high level -  PTFE and "in-oil" military grade capacitors, Ohmite HV resistors, Caddock resistors, Vishay 0.1% resistors, electrolytic capacitors for 105C of operating temperature, last generation of semiconductors, Schutzinger laboratory grade connectors, pure silver-ofc input wiring…

Transmitter 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 wound nano-crystalline core transformer
          -Premium step of upgrade : pure-balanced input realised with hand wound silver-ofc wired nano-crystalline core transformer

  NOTE: Protect covers should always be placed over output (big) tubes due to safety!


Technical Specification
Name Value
Type Single Ended Class "A" Triode
Power Output max. 80 Watts @ 1 kHz
Frequency Response 8 Hz to 110 kHz -3dB
Input impedance 100 k ohms parallel with 100pF
Input Sensitivity 1.5 V RMS for 80 Watts
Gain 24.50 dB (x18.8)
Noise 110 dB below rated output "A" weighted
Tube Complement 2 x 6N6P, 1 x QB5/1750
Power Requirement 110 to 240 VAC @ 50 to 60 Hz, 370 VA max. (set in factory)
Dimensions 11.8" (300 mm) wide ´ 20.9" (530 mm) deep ´ 11.8" (300 mm) high
NET Weight approx. 89 lbs (40 kg) unpacked / per block
TOTAL Weight approx. 220 lbs (100 kg) packed in polypropylene crate / per pair

Design Features

- single-ended pure class A mono block power amplifier
- zero global feedback
- all triode (pure tube) configuration
- short signal path
- output section-direct heated triode connected type Philips (or other western manufacturer equivalent) QB5/1750 (N.O.S.) output tube
- driver section - 6N6P tubes by military grade and (N.O.S.) grade
- hand coiled output transformer (custom designed for NAT)
- silent operation power supply unit
- additional polypropylene capacitors in power supply
- regulated power supply for all stages (including the output one)
- automatic bias current control for the output tube
- soft start operate to improve entire reliability
- hand assembled all modulated chassis
- high mass laboratory grade output connectors
- gold plated PTFE insulated RCA input connectors custom ordered from NAT
- extensively used computer numeric control machines (CNC)
- 4/5" (20mm) thick quadruple aluminum front panel
- cover cage pipe or laminate type (optional)

Specifications are subject of change without notice