Vacuum I.N. is NAT’s flagship MM phono stage and the fullest expression of its vacuum inverse-network concept. Fourteen military-grade Nuvistor triodes form a zero-feedback, pure-Class-A circuit in which the RIAA equalisation is performed through a vacuum-field network rather than a conventional RC or LCR section.

Both plate supply and valve filaments are battery powered, with automatic charging handled by a separate low-radiation supply. Hand-wound nanocrystalline chokes and output transformers provide dedicated magnetic elements for each channel, while the output stage can be configured for true RCA or balanced XLR operation.

The construction combines a gold-plated PTFE circuit board, precision Vishay resistors, selected capacitors and an extensively machined modular chassis. NAT specifies more than 100 hours of burn-in for each completed unit.