Audio Research LS1 Line Stage Hybrid Tube Amplifier - Complete with Box and Serviced

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You won't find a better hybrid tube line stage in this price range, especially made in the USA!

Comes complete with its original box and manual as shown in our photos.

This piece also just underwent a routine service in our shop, which included replacement and relocation of the low voltage supply regulator to its own dedicated heat sink away from the main PCB.

The 6DJ8 tube was replaced with an Amperex Bugle Boy (Holland) tube with confirmed balanced sections, fully tested on our in-house modern Amplitrex AT1000 tube tester.

The filament supply dropping resistors were adjusted to provide optimal supply voltage for the 6DJ8, and the Output FETs were replaced with a matched set provided by Audio Research. We also replaced the two large axial filter capacitors.

This unit was previously upgraded in the past, featuring Mundorf M Caps.

The SkyFi Testing Process for Preamplifiers:

We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and transistors are checked for signs of stress or damage. Special attention is paid to the power supply which is the most common source of failure for preamps. We then power up the unit and run a simple 1k sine wave while monitoring the low voltage output on an oscilloscope for signs of distortion or noise to get a baseline.

At this point we will lubricate and clean all switches and potentiometers (that are not sealed) with a high quality contact cleaner, and then re-test all functions for any signs of noise or scratching.

Final testing involves putting actual music through the preamplifier We have learned over time that some issues are only noticeable to a trained ear while listening to a familiar source material. Our test bench has reference vintage KEF speakers that we are super familiar with which will quickly reveal any discrepancies. Some preamps will then move into the listening room where they will be tested with our in-house reference system.

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.