Inovative Audio Manufacture

Balanced Dual Mono Zero Feedback Vacuum Tube Line Stage

NAT Audio introduced last version of tube balanced preamplifier called "Symmetrical Vacuum". New line stage is completely in dual mono topology also with zero feedback all triode vacuum tube design.


 There is fourteen(14) tubes that works in perfect symmetry, means seven(7) per each channel.

Design based on fact that preamplifier may work perfect in both type of operation-balanced (xlr) and single ended (rca).

Also, attenuation network is realized with 56 high reliability silver contact relay. Only one (vishay) resistor is always to the signal path (shunt type)!

"Symmetrical" may drive any known power amplifier no matter of type or internal impedance (compatible with input impedance of 600ohms). It also means that interconnect length between pre and power amplifier may be of enormous value.

Remote control as standard option is made from solid block of aluminum.


Technical Specification
Name Value
Frequency Response 0.07 Hz to 300 kHz – 3 dB ; 20 Hz to 20 kHz ± 0.01 dB
Noise < -95 dB "A" weighted @ 1V rms
Gain 15.5 dB (X 5.6 Phase status: non-inverted (0 degree)
THD & N < 0.03 %  20 Hz to 20kHz @ 1V rms
Input Impedance > 10 kohms single ended: >20 kohms balanced
Stereo Separation > 100 dB @ 1 kHz
Tube Complement 2 X EY500A, 4 X 6N1P-EV, 4 X 6N2P-EV  &  4 X 6P30B-R(miniature)
Output Impedance < 100 ohms on single ended ;  <200 ohms on balanced
Power Requirements 110 VAC or 220 VAC @ 50 to 60 Hz, max. 100 VA
Dimensions 19" (483 mm) wide ´ 18" (455 mm) deep ´ 6.5" (165 mm) high (max.dimensions)
NET Weight approx. 60 lb. (27 kg) unpacked
TOTAL Weight approx. 77,2 lb. (35 kg) packed in wooden box


Design Features

- full dual mono construction with 14 tubes (7 per each channel)
- zero feedback design
- all triode pure class A configuration
- double regulated, hybrid output high precision power supply
- high current tube 6P30B-R(miniature)  N.O.S. & longlife
- vacuum tube power supply rectification with high-voltage EY500A booster diode
- high quality audiophile grade capacitor of high capacitance on signal path
- polypropylene capacitors in high voltage power supply
- two low density silent power transformers each per channel for analog stages custom made for NAT
- soft start operate
- relay network attenuation (shunt type realised with 56 relays)
- gold plated teflon insulated RCA jacks with gold plated XLR balanced connectors
- hand assembled all aluminum modulated chassis
- laser engraved front panel made from triple separate aluminum block of 20mm thick
- laser engraved remote control made from solid block of aluminum
- extensively used computer numeric control machines (CNC)

Specifications are subject of change without notice


Related items