The M6 Line Preamplifier from Audio Note (UK) uses a single-ended, zero feedback circuit topology, which is known for its simplicity and linearity. This design eliminates the need for a phase splitter, which can introduce crossover distortion in other amplifier designs.

By using a single-ended, zero feedback circuit topology, the M6 Line Preamplifier is able to achieve a high degree of linearity and signal purity. This design demands pure Class A valve operation, which means that the output signal is always amplified by the same amount, regardless of the input signal level. This mode of operation can provide a more natural and musical sound, but also requires more power and generates more heat than other amplifier classes.

The M6 Line is equipped with a dedicated Audio Note (UK) stepped attenuator for each channel. This is a high-quality volume control that uses a series of precision resistors to provide accurate and repeatable volume adjustments.

This preamplifier features a line stage based on ECC82 and 7044 vacuum tubes, which are known for their low noise and high linearity characteristics. The preamplifier also uses a 6X5 valve rectified power supply, which is based on the Galahad PSU used in the M10 preamplifier. The power supply incorporates an ECL82 tube for voltage regulation and a 5651 tube as a voltage stabilizer. These tubes are carefully selected and implemented to provide stable and reliable power to the amplifier circuit.

Throughout the circuit, Audio Note (UK) Silver wiring, tantalum resistors, and custom electrolytic capacitors are used to provide a high level of performance and sound quality. Additionally, the preamplifier features Audio Note (UK) Copper foil signal capacitors, which are known for their transparency and detail retrieval.

The M6 Line Preamplifier also uses in-house designed and manufactured custom Audio Note (UK) output transformers, which feature a UHiB c-core, Copper primary, and Silver secondary. 

Overall, the M6 Line Preamplifier is designed to provide a simple, linear, and musical signal path, intended to minimize distortion and provide a transparent and natural sound.