Single Ended Mono Block Power Amplifier

Microwave is a new power amplifier made by NAT standard with all tubes by military grade in pure class A, single – ended type, zero global feedback topology.

Main facts:

  • First high power metal-ceramic tube zero-feedback single-ended power amplifier globally, unique device
  • Most compact in the class (19″x19″x6.5″)
  • Most efficiency in the class (280W of power consumption for 100W of pure tube single-ended class A)

Microwave gives an opportunity to listen favorite music on two different mode. In fact, it represents two types of amplifier in one unit .With power of 100W or 40W (on lower mode) in single – ended technique there is a capability to drive almost any type of  loudspeaker (with lower or higher sensitivity equally).

Military (N.O.S) GI-7B – output triode tube – represent high technology in vacuum manufacturing as metal-ceramic device. Potential of output tube is 350W of heat dissipation while we use not more then 65%, further it decrease working temperature point – means additional improvement of amplifiers reliability. Construction of output tube GI-7B  is very robust also in mechanical domain – there is no microphonic effect for negative influence to the sound reproduction. Special designed metal-ceramic tube has much lower microphonic then the standard glass bulb type!

For the audiophiles with higher sensitive loudspeaker there is a low mode option (position on rear panel) to lower the output power from 100W (in standard mode) to 40W, also to decrease power consumption of output tube – means no need for extra heat dissipation that cause additional improvement of reliability.

Input-driver tube is also made by military standard indicated like N.O.S. (new old stock) grade.

Hand crafted wide-bandwidth output transformer (custom designed for NAT ) is used in this unit. Output transformer contains no less then 56 separated different layers. Bandwidth is from 6Hz – 70.000Hz. That is extremly good result for single – ended zero feedback operation mode. Output has separate taps for 4 ohms and 8 ohms speaker load (may drive any load from 2 ohms to over 32 ohms). By specific technical approach mention output transformer in combination with output tube- GI-7B,  may drive easy any type of loudspeaker with damping factor equaly as in push-pull tube configuration. Zero global feedback concept is well known as the best solution for purity of sound reproduction. That means good for driving of all type of speaker equally (electrostatic, dynamic or other types).

Power supply section speaks for itself. Main transformer is designed for double the power then Microwave consume (approx. 600W) with totally silent operation. There is separate voltage regulators 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. Equivalent energy from power supply is huge (example for bass response down to 20Hz, it is equal to no less then 8000 Joules of related capacitor type energy). Polypropilene type of capacitors is used for the single output tube high voltage section. Soft start additionally improve reliability of entire amplifier by avoiding voltage stress during turn-on procedure.

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

Quality of electronic material that is used inside Microwave is impressive – beside all military quality (N.O.S) tubes there is industrial polypropilene grade capacitors, 0.1% Vishay’s resistors, electrolytic capacitors for 105C of working temperature, last generation of  IXYS semiconductors, WBT output connectors, pure silver input wiring…

Amplifier works properly at all world wide AC line voltage from 100 – 250 VAC, 50-60Hz (different transformers are used).

Note: Last generation, high tech. FAN is used inside a chassis with almost noisless operation. From distance of only 10″ (25cm) and up FAN is totaly noisless.



Technical Specification
Name Value
Type Single Ended Class “A” Triode
Power Output 100 Watts @ 1 kHz
Frequency Response 6 Hz to 70 kHz -3dB
Input impedance 100 k ohms parallel with 100pF
Input Sensitivity 2.0V RMS for 100 Watts
Gain 23 dB (x14)
Rise Time 2.0 microsecond
Noise 110 dB below rated output “A” weighted
Tube Complement 1 x 6N2P-EV & 1 x GI-7B military type
Power Requirement 110 to 240 VAC @ 50 to 60 Hz, 280 VA max. (set in factory)
Dimensions 19″ (483 mm) wide ´ 19″ (483 mm) deep ´ 6.5″ (165 mm) high
NET Weight approx. 86 lbs (39 kg) unpacked / per piece
TOTAL Weight approx. 110 lbs (50 kg) packed in wooden box / per piece


Design Features

– Single – Ended pure class A mono block power amplifier
– zero global feedback
– triode based configuration
– short signal path
– DC coupled circuit (only output transformer on signal path)
– military specification power metal-ceramic type triode GI-7B (N.O.S.) output tube
– CE comfortable regarding maximum DC operating voltage
– driver section use 6N2P-EV input tube (N.O.S.) – long life grade
– output transformer custom designed for NAT – 1000W of power
– power transformer custom designed for NAT – 600W of power
– polypropylene capacitors in HV power supply for GI-7B (N.O.S.) output tube
– regulated power supply for all stages (including the output)
– automatic bias current control for the output tube with long term stability
– switch selector for 40W & 100W of power oputput (on the rear panel)
– soft start operate to improve entire reliability
– hand assembled all modulated chassis
– WBT output connectors
– extensively used computer numeric control machines (CNC)
– 0.6″ (15mm) thick double aluminum front panel
Specifications are subject of change without notice

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Jesse LueceroMicrowave