NAT Audio's Statement-Level Line Stage Combines Battery Power with Tubes

by The Audio Beat | July 23, 2010

AT Audio's Magnetostat ($17,500) is a tubed, transformer-coupled, class-A, no-feedback line-stage preamp that uses a wealth of impressive parts. These begin in the power supply, which has long-life Panasonic batteries to store the unit's power, making the Magnetostat impervious to power-line anomalies. New-old-stock military-grade 6N30P-DR tubes are used, along with handmade, wide-bandwidth, custom transformers. There are separate transformers for each channel and for single-ended and balanced operation. The unit's volume control is a computer-controlled, 96-position attenuator that puts a single lab-grade resistor in the signal path. To maintain signal purity, the Magnetostat has no capacitors in its signal path and uses pure-silver wire at its inputs. Both single-ended and balanced inputs and outputs are included.

The Magnetostat's physical construction is said to be "very robust" in order to minimize the effects of vibration and resonance on the tubes. The single chassis, which weighs 120 pounds, is constructed of aluminum plates. The preamp's remote control is machined from a single aluminum block, in keeping with the unit's over-built construction.

The Magnetostat monitors the state of its batteries, automatically recharging them when needed. It also keeps track of accumulated tube life, helping owners know when it's time to replace the tubes.