I review Empirical Audio's pricey Off-Ramp 4 asynchronous USB–AES/EBU converter with its Monolith 1 battery supply in the forthcoming December issue and was impressed by the quality of its engineering as well as by its sound quality. At RMAF, Empirical's Steve Nugent showed me the Overdrive Ultra D/A converter ($10,000–$15,000), housed in a bronze case, which is well-damped. The DAC uses the Off-Ramp 4 circuit as its USB front-end and features just one analog stage following the I/V converter. Unusually, this uses a bipolar emitter follower instead of the common FET buffer. The digital circuitry is powered from the Monolith, feeding 12 Hynes-type regulators, though Steve Nugent feels that the analog stage sounds better when powered from a conventional AC-derived supply. The volume control in the DAC is elegant in that it reduces the reference voltage to the DAC chip, thus maintaining full digital resolution. There are two choices for full-scale output voltage.

The Empirical bronze DAC was being demmed in a system featuring YG Kipod Signature speakers ($49,000/pair) driven by Empirical-modded Parasound Halo JC 1 monoblocks ($10,000/pair). A Mach 2 SL2 server running Amarra proved audio data to the Empirical DAC; cabling was all Balanced Power Technologies; and the room had been treated with GIK traps, panels, and diffusors.