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Reference Zero Feedback Balanced Line Stage

After over then fifteen years in production NAT replaced Symmetrical with new Symmetric line stage - as a new modern looking hybrid type only balanced operation unit!

Symmetric is a newest reference pure balanced line stage made by NAT standard - transformer coupled, class A with zero feedback circuit configuration. Special selected RF linear FET with vacuum tube is used!

 Dual Single-Stage Single-Ended active device form amplification circuit in Symmetric.

Symmetric represents a true dual mono construnction - totally separate one channel from another.

Hand coiled wide-bandwidth output transformer is used inside Symmetric.

Open bandwidth of output transformer is from 2Hz - 1MHz. Symmetric has square wave response that is almost perfect! It is indicated with extremely linear (non sub-resonant) frequency response. Nano-crystalline transformer core is used as the best option for audio - for crystal sound transparency!

Symmetric may easy drive any type of interconnect cable at very long length due to fact of very low output impedance.

Symmetric is equipped with two gain mode - low at 10dB and high at 16dB that should be selected with rear panel switch.

 Zero feedback concept is well known as the best solution for the purity of sound reproduction.

There is no any capacitor on direct or indirect signal path.

Attenuation in Symmetric is based on high reliabillity relay (pure silver with gold plated contacts) network that is computer controlled. There is 96 position of attenuation with only one (single) laboratory grade resistor on signal path at any setting point!

Power section with high capacity (approx. 500.000 uF of capacitance) is used as the best solution for output active device. There is more than 300 joules of energy (not common energy even for the high power amplifiers)!

There is separate voltage regulators also for all additional (non signal path) stages.

Sound quality of Symmetric is totally independent from line voltage instability and influence of wide variety noise that could be coupled across.

Symmetric is equipped with remote control unit made from solid block of aluminium.

Quality of electronic that is used inside Symmetric is on high level - special selected RF linear FETs made by military spec., 0.1% 5ppm Vishay resistors, nano-crystalline transformer core, capacitors of very high capacitance, teflon based gold plated PCB for attenuator network, gold plated XLR connectors, teflon isolated all silver-ofc internal wiring...

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

 

Technical Specification
Name Value
Type Zero feedback
Operation Pure balanced (XLR)
Frequency Response 2 Hz to 300 kHz, – 3 dB ; 20 Hz to 20 kHz, ± 0.05 dB
Signal to Noise Ratio >110 dB
Gain 16 dB (X 6) @high gain or 10dB (X 3) @low gain
THD & N <0.06 % @2Vrms
Input Impedance >20 kohms
Output Impedance <180 ohms @low gain or <350 ohms @high gain - both ref.to XLR
Stereo Separation >near infinite (dual mono)
Power Requirements 100 VAC or 240 VAC (50 to 60 Hz), max. 50 VA
Dimensions 19" (483 mm) wide ´ 16" (400 mm) deep ´ 6.3" (160 mm) high
NET Weight approx. 60 lb. (27 kg) unpacked
TOTAL Weight approx. 77 lb. (35 kg) packed

 

Design Features

- transformer coupled circuit (without any capacitor on direct or indirect signal path)
- dual single-stage single-ended design (in balanced configuration)
- zero feedback design
- approx. 500.000uF of capacitance for analog power supply section
- true dual mono construction
- custom designed ultimate wide-bandwidth hand coiled nano-crystalline core output transformers (with near perfect square wave response)
- vacuum tubes of N.O.S. (new old stock) grade - booster PY88 type in power supply
- separate transformers for digital control and analog supply (3 units in total)
- relay network attenuation (shunt type realized with 56 relays)
- remote control made from solid block of aluminium
- all aluminium modulated chassis
- front panel made from 15mm thick aluminium material
- gold plated connectors

Specifications are subject of change without notice