Power Amplifiers

Burson Soloist Headphone Amplifier


Burson Soloist Headphone Amplifier On The Bench – By Chris Heinonen

The Burson Soloist has three levels of gain: High, Medium, and Low, depending on how hard your headphones are to drive. Low puts out a maximum of 2.75V, Medium puts out up to 5.5V, and High puts out 9.1V maximum. I did most of my testing at the medium level at 5V of output using AKG K701s as the load on the amplifier.

With a 1 kHz tone and 2V output, THD+N was only 0.01%. The 2nd and 3rd harmonics were both over 100dBV below the fundamental frequency. Moving this up to 5V drops that THD+N down to 0.002%.

With a 10 kHz tone, THD+N was 0.005% at 2V of output. Here the 2nd and 3rd harmonics are both almost 100dB below the fundamental respectively. I also tested this with High Gain instead of Medium Gain and the THD+N was the same, though the 3rd harmonic was higher than the 2nd harmonic, instead of being the opposite at medium gain.

Using 60 Hz and 7kHz IMD tones we see an IMD value of 0.03%, and there were no real sidebands, and the only harmonics visible were very slight at 2V. There was a single 2nd harmonic for the 7 kHz tone that is virtually invisible. When I pushed the output to maximum for medium gain, the IMD remained the same, though you can now see that harmonic at 14 kHz much better now.

Using 19 kHz and 20 kHz IMD tones, the 18 kHz and 21 kHz sidebands were close to 90 dbV below the fundamentals, allowing a good amount of headroom. There was no B-A peak aside from the low frequency noise visible in all the charts.

THD+N is a little higher in the deep bass area, but quickly falls to 0.0025% or so and stays there for the rest of the frequency spectrum. This matches up with what we saw on the 1 kHz and 10 kHz tests.

Aside from some noise in the lowest octaves, which was still around 75 dBV below the fundamentals, the Burson tested very well when used as a headphone amp.

Curiously, when used as a preamp, the RCA outputs put out the same voltage levels as the headphone jack. Talking to Burson, they've designed it this way to work well with a wide variety of amplifiers, so you can tailor the gain applied by the Burson to match your amplifier. Performance as a preamp was virtually identical to as a headphone amp, so I've not run the graphs as they are the same.

The only thing that concerns me with the Burson Soloist is the lower octave noise I saw. However this also showed up recently on a Blu-ray player I tested, so I believe there is some low-level noise in the power where I'm testing, that I can't avoid. Overall performance was very good, with plenty of power to drive any headphone and very good overall performance.