Athena is a tube output DAC with ROHM conversion, native PCM up to 32-bit/384 kHz, DSD512, seven digital inputs, and balanced transformer outputs.
Zesto's new DAC teaches us the value of tubes in modern gear
George and Carolyn Counnas, along with a secret team of digital specialists, have been hard at work finishing up Zesto's newest product, the Athena DAC.
This $15,000 tube DAC uses a high-end digital front end based on a ROHM chip and a tube output stage with two ECC82/12AU7 tubes and two ECC832/12DW7 tubes. It's a Class-A, dual mono design, with the 12DW7 tubes handling the input from the DAC and driving the output tubes, and the 12AU7 tubes driving true differential, balanced output transformers.
We spent a few days last week with the Athena and came away with some new insights on the use of vacuum tubes in cutting-edge digital audio.
Tubes Can Be Dead Silent
George Counnas is one of the "hybrid" generation of engineers. In engineering college, he split his time between tube circuits and the then-emerging solid-state technology. He also worked for Decca Radar and Decca Navigator, designing systems that had to endure training and combat duty aboard fighter planes. George doesn't use tubes because of nostalgia, but because they are engineering marvels that still have pride of place in a modern audio system. He knows how to design tube circuits that are fast, open, and totally silent. This allows the Athena to produce sound from seemingly nowhere, with the same startling realism as Chord DACs, which come from a very solid-state school of thought.
Tubes Are Fast
Because their signal is moving through a near vacuum, tubes are extremely fast. "The challenge with tubes," says George, "is designing the rest of the circuit to keep up with them." The result is that tubes don't have to sound gooey and tubey, as anyone who has ever heard a Zesto amplifier will assert. Tubes can hit hard, and do so with wideband slam and sparkle.
Tubes Change the Filtering Equation
The breakthrough for the Athena came when George realized that his tube circuit simply didn't "see" the ultrasonic images that can result when interpolation or reconstruction filters are omitted from the digital path. This meant Athena could use native conversion without upsampling or additional digital filtering, delivering a direct, natural sound.
Musicality Is The Only Constant
From PrimaLuna to BAT to Zesto to Phasemation, there is a huge variety in the voicings of tube audio, and the only broad comment we can make is that tube audio is consistently enjoyable. The Athena has this quality too: a sense of flow, ease, and realism that we often call musicality.
Find Your Vacuum Tube Darling
Kevin Deal, Upscale Audio's founder and the Tube Guru, often says that people eventually move from solid-state to tubes, but very rarely the other way around. Solid-state fans are often held back by oversimplified notions of how tubes sound. For example, if you think 300B tube amps are "romantic" you should hear how a Phasemation SA-1500 playing through a Klipsch La Scala can knock you out of your listening chair. It's about finding that magical combination, and whether it's power amps or DACs, all-tube or hybrid, there's a place for vacuum tubes nearly anywhere in the chain, and for nearly any kind of listener.