The Soloist Takes A Great Leap Forward
August 16th, 2012 -- by Chris Martens
Long-term Playback readers know that we are great admirers of the Australian-made Burson Audio HA-160 headphone amplifier and AB-160 audio buffer. Both products make sense to us, and the HA-160 in particular offers a ton of value for the money. But now, Burson has created a new flagship headphone amplifier called the Soloist ($999), which can also serve ably as a three-input stereo preamplifier. Once you consider how good the HA-160 is you might rightly expect it to be a tough act to follow, and it is. Even so, Burson claims the Soloist sounds even better, offers considerably more flexibility, and—dare we say it—is potentially an even better value. Can the Soloist back up these claims? That’s precisely what this review aims to find out.
- Improved chassis vis-à-vis the original Burson HA-160. We have long admired the construction of Burson chassis, which feature sturdy, non-resonant side panels carved from (very) thick sheets of aluminum of slightly different thicknesses, to help fight unwanted resonance. What is more, Burson chassis have been designed to serve as “unified heat sinks” for the pure class A audio circuits found within. These characteristics carry forward into the Soloist, but with two improvements:
- Improved panel joining techniques are said to require fewer parts while providing “higher structural integrity” and “higher precision” of fit, which is saying something when you consider that Burson amps have always been built like Aussie interpretations of Swiss bank vaults.
- Burson says exterior panel surfaces are now treated to extra polishing processes, so that all surfaces—including the base plate—“can be described as beautiful.” And indeed, they are beautiful.
- New “symmetrical transistor” amplifier input stage using FET (Field Effect Transistor) devices.
- In the process of creating the Soloist, Burson invested in a 6-month development effort to create an even better sounding input stage than the one found in the original HA-160, where the initial concept had been to design a “symmetrical-transistor” input stage based on bi-polar transistors.
- The resulting bi-polar device-powered input stage measured very well and sounded good in terms of dynamics and detail, but it did not fully meet Burson’s sonic expectations—especially not in the all-important midrange.
- Unwilling to settle for compromises, Burson went “back to the drawing board” for another 12-month-long development effort to create an all-new symmetrical-transistor input stage based on FET devices. The new input stage, which is at the heart of the Soloist, offers what Burson terms a “lively and coherent sound that is a combination of all the strengths of FET and bi-polar transistors.”
- “Less-is-More” design approach:
- Burson has long avoided using IC-type (integrated circuit) opamps in its products, arguing that even the best IC-type devices sound inferior to discrete transistor designs. The firm also passionately believes that simpler audio circuits generally sound better than complex ones.
- For the Soloist, one key goal was to “remove as many components from the signal path as possible while still maintaining ideal operational levels.” The Soloist input stage uses just 21 components in the audio signal path as compared to 32 components for the HA-160 input stage or 53 components for a typical NE5534 IC opamp-based input stage. Burson describes the benefits of its newly simplified circuit with this slogan: “Less Blockage, More Music.”
- The Soloist provides considerably higher power output (4W @ 16 Ohms) than the HA-160 did (250mW).
- The Soloist incorporates a very low-noise power supply.
- The Soloist incorporates what Burson terms a “high resolution volume control”; that is, a stepped attenuator-type volume control based on precision-matched, high-quality/low-noise resistors. Burson builds and assembles this volume control in-house.
- More usable features: The original Burson HA-160 provided a single stereo input and two output jacks, each optimized for a different impedance range of headphone. The Soloist goes much further to provide:
- Three stereo analog inputs.
- One variable-level stereo analog output, which gives the Soloist preamp capabilities should owners wish to use the Soloist to drive power amplifiers and thus full-size hi-fi systems.
- Three switch-selectable levels of gain, to adapt the Soloist for use with headphones of varying impedance/sensitivity levels.
- The multi-level gain switches also affect the Soloist’s gain levels as a preamplifier.