One or two days after the amplifier arrived, my local headphile friends wanted to audition the amp so I took it to the Jaben store and all of us auditioned the Soloist and we A-Bed it to the Burson HA-160D which belongs to a friend of mine. They were just as excited about the Soloist as I did, mostly because of the same reason: they’ve never heard the HE-6 with this sort of a bass and midrange body. Not only does the Soloist add bass body, but it also adds a stronger impact than the HA-160D does. I think we can give credit to the 4 WPC output for that impact.
In terms of sound signature, the Soloist had the thickest body out of the trio of amplifiers. The RSA Dark Star and the HA-160D were more linear, with the Dark Star being more spacious while the HA-160D having a more forward sound and a better PRaT. I enjoyed the fact that the Soloist not only adds body to the HE-6, but also that it relaxes the treble more than the HA-160D and the Dark Star. Comparing the Soloist to the HA-160D is like comparing the Sennheiser HD650 to the HD600.
Technically, the HA-160D had a wider soundstage and a clearer articulation, while the Soloist had a better depth in the soundstage. I also felt that the Soloist had a more natural decay, while the HA-160D is more abrupt on the decay cutoff. With headphones that never really lack bass and midrange body like Audez’e's LCD-2 and Senn’s HD650, I think that the HA-160D is still best, though by a slight margin, simply because I was getting better bass articulation and a more “correct” treble presentation. Paired with the Soloist, I still enjoy the LCD-2 and the HD650 highly, so it’s not like the Soloist are enemies with the two headphones. Especially with the HD650, it’s quite noticeable how much better the depth on the soundstage presented by the Soloist is, compared to the relatively flat HA-160D.
With the Hifiman HE-500 and the HE-6, I think the Soloist is my number one amp for those headphones now. I also had the chance to pair the Soloist with Mr. Speakers’ Mad Dog headphone and the two pair very well. A friend of mine who owns a recording studio and is a music engineer was impressed to hear his Mad Dog headphone being transformed by the Soloist.
I don’t really have the habit of driving IEMs with desktop amps, even more 4 watts amplifiers. For those of you who do, the Soloist is among the quietest desktop amp I’ve auditioned and had absolutely no noise issue with sensitive IEMs.
Some Notes About Burson’s Volume Attenuator
The Burson comes with a discrete volume attenuator which in theory is a mechanical switch with 24 different stops, all linked to a different value resistor. Stepped attenuators are agreed by the audiophile community to provide a better quality signal transfer path compared to standard sweeping-taper potentiometers.
When I compared the Soloist to the HA-160D which is about one year old, there was a problem in the volume control where everytime you move the position of the switch, there would be a loud “pop” noise that’s audible on the headphones. Not very pleasant, and my friend the owner told me that the pop got louder as the amp ages. The first thing I thought of is “bad contacts”. So I took a can of electronic contact cleaner, specially developed for cleaning electrical signal contacts, and I sprayed the attenuator unit with it. Afterwards the pop disappeared completely.
Apparently the same problem had started to build up on the Soloist’s volume control, though in much milder level and with much lower pop sound. Again the contact cleaner would solve the problem, but I thought that it would be good for Burson to improve the sealing on the contacts.
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