This a is a K Prefix that was redone by Chris West at AV options to include the most recent black SNAIC(cryogenically treated) and RF mod. He replaced the input resistors with Vishay Z-foil resistors and replaced all the tantalum capacitors. It is currently terminated with a Cardas DIN plug for use with non Naim arms, but comes with the ARO plug too. The cost of the work done by AV options is more than Im asking for this unit. No low balls please. Only selling because I replaced it with a Superline. FWIW I replaced a stage line with this unit and it was considerably better in terms of dynamics and transparency, a definite upgrade.