Headphones and Earphones
- Written by John E. Johnson, Jr.
- Published on 22 July 2010
While headphone amps are not in every audio enthusiastâ€™s system, they are still engineered with many of the same design choices as other more common components. One of the main choices to be made is whether to build a full featured but complicated component, or a simple, barebones component that has thrown all the nice but unnecessary features over the side. Burson Audio is an Australian company known for making the latter. When I tested the PI-100 integrated amp a couple of years ago, I found a component with some rough edges, and the bare minimum number of features necessary to function, but with absolutely transcendent sound quality. Burson has said their new HA series of components has knocked the rough edges off their build quality while keeping the amazingly good sound quality and value. The HA-160 is Bursonâ€™s all out assault on the headphone amplifier genre, and it contains all of Bursonâ€™s unique tricks. The question is, does it fix the negative parts about earlier Burson products while retaining their fantastic sound and great value?
- Input impedance: 47 KOhms
- Frequency response: 5Hz (-0.3dB) to 35 kHz (-1dB)
- Signal to noise ratio: >98dB at 0dB gain
- THD: <0.001% at 6mW/300 Ohms
- Channel separation: >70dB/10kHz
- Output power: 650mW/300 Ohms, 800mW/60 Ohms
- Output impedance: line out 60 Ohms, phones out 5 Ohms
- Power dissipation: <10W, internal, regulated power supply
- Dimensions: 180mm x 250mm x 80mm
- Connectors (audio): 2 x phone jacks 6.35mm
- 2 x gold plated RCA connectors with Teflon isolation
- Weight: app. 4.5kg
- MSRP: $699 including shipping
All Burson products including the HA-160 share several unique design features, other than simplicity. The first and foremost Burson design philosophy is to use no integrated circuits anywhere in their products. Everyplace a typical manufacturer might use an op-amp, a voltage regulator or the like, Burson designs and implements that functionality from scratch using transistors. One of Bursonâ€™s signature items is the Burson HD Audio Op Amp, a custom built circuit board made with dozens of matched transistors and other precision discrete parts that provide the functionality of an IC op-amp. This component was originally designed for the DIY market to replace IC op-amps as an upgrade. Burson then began to build on this design in all their products. The PI-100 had this op amp as a major component in the preamp section, and it is also the core of the HA-160. The output stage is also both entirely discrete and fully Class A. In addition to the gain stage, the voltage regulators in the power supply are also entirely made from discrete components. The volume control is entirely passive, and is implemented as a 24-step attenuator with 1% resistors. This simple switchable voltage divider puts only a single 1% resistor in the signal path. Two high quality Â¼â€ phono jacks are provided, one for low impedance (25-150 ohm) headphones, and one for higher impedance (150-500 ohm) headphones. A single pair of RCA inputs is provided, along with an IEC power socket.
The quality of the electronics in the HA-160 is first rate, and the case is a great improvement over previous Burson products. The 6mm thick aluminum case is much beefier and well put together that the PI-100. The HA-160 let me down in two ways. The first was very minor: my 160 came with an Australian power cord and the power supply set to 230V. This was easily fixed since the HA-160 accepts any IEC power cord, and the power supply voltage changes with a flip of a switch. The second was a bit more annoying. One of the 24 steps in the attenuator (in the middle of the range) was shorted. When I selected this setting, the HA-160 went to maximum volume. With my Denon AH-D7000â€™s this resulted in very loud but not damaging volume level. Had I had a more sensitive pair of headphones, this issue could have gotten very expensive.
I set up the HA-160 on my desk using my Headroom ultra desktop as the DAC. It was fed a 24 bit 96 kHz SPDIF signal from an M-Audio 2496 PCI soundcard. I ran the HA-160 at moderately high volume level driving my Denon AH-D7000 over a weekend. All the Headroom processing features were turned off during my listening. After the break-in, the HA-160 immediately sounded brilliant.
The first and most clear improvement over the Headroom Ultra Desktop (which is a great amplifier, by the way. I own one), was an improvement in dynamics. Transient impact and overall â€œalivenessâ€ gained ground. The Denon headphones have absolutely fantastic, skull crushing bass when called for, and the HA-160 really brought out the true measure of power in the low range with the Denons, without making them sound bloated or heavy. In fact, the HA-160 managed to add power, impact and depth, while making them simultaneously sound lighter on their feet.
My favorite bass heavy album of late, Daft Punkâ€™s Human After All was absolutely fantastic. Super deep, powerful and fast bass, with every last bit of texture and detail you could hope for. In addition, the top end was even more airy and extended than the Headroom amp, without sounding even a trace hard or harsh. The upper midrange was particularly good. Regina Spektorâ€™s Begin to Hope raised the hair on the back of my neck with its tonal purity and realism, particularly with Spektorâ€™s unaccompanied voice. The place where the HA-160 gave up something to the Headroom amp was in imaging and soundstaging. Headroomâ€™s â€œcrossfeedâ€ image processing technology, that mixes signal from one channel into the other through a time delay, really does result in better imaging. Compared to the Headroom, images in the HA-160 were less focused and precise unless they were exactly in the center of the soundstage. The soundstage collapsed into three locations: center, left and right. There was little or no clear depth information. The Headroom amp had a continuous soundstage from right to left, and offered plenty of depth information, taking the soundstage outside my head. As usual with the Headroom system, the sound seemed to come from above my head, not in front of it, but the spatial information and presentation was considerably better than the HA-160. I guess what it comes down to is what you find important. If tonal purity and dynamics are the most important, than the HA-160 is the winner.
If you love imaging and soundstaging, then the Headroom is the way to go. For me, I canâ€™t give up the spatial superiority of the Headroom, but I still think the HA-160 is a wonderful amp. With the addition of the Headroom crossfeed, it would be perfect for me, but that is definitely not the Burson way.
I measured the Burson HA-160 using a M-Audio ProFire 610 Firewire sound interface with Spectra Plus FFT analysis software. I used both 100 ohm and 500 ohm resistors as a loads, with the volume setting trimmed to produce a 1V p-p output level. Measurements were made with 24 bit, 192 kHz sampling and 96 kHz audio bandwidth, and the frequency response of the 610 was corrected using a loopback measurement. The forest of low level spurs in the single tone measurements results from pickup from the air due to the unshielded load resistor connected to the test leads with alligator clips.
Total harmonic distortion plus noise (THD+N) was measured with a 1 kHz test tone into both the 100 ohm and 500 ohm loads. Into 100 ohms, the result was 0.015%, while into 500 ohms, the result was a bit less (0.011%). This is preamp level distortion as youâ€™d expect.
THD+N versus frequency was pancake flat into both loads up to the point where the anti-aliasing filter kicked in near 96 kHz.
Intermodulation distortion, measured with a pair of tones at 7 kHz and 60 Hz, was virtually unmeasurable. Spectra Plus says 0.0009% for both loads, but that is below the level that I trust the test equipment to measure.
Test tones at 19 and 20 kHz produce a 1 kHz intermodulation product 100 dB down from the fundamental tones.
Frequency response is also flat as a board into both loads, but level is higher into the lower impedance load with the same volume setting.
The HA-160 is a perfect example of the performance that Bursonâ€™s design philosophy can deliver. The no-frills completely discrete design delivers unmatched dynamics, tonal accuracy and smoothness at a reasonable cost. The simple design does give up imaging and soundstaging performance compared to the benchmark Headroom Ultra Desktop, but that might not be a deciding factor for many potential buyers. If you value dynamics and tonality over imaging and soundstaging, the Burson HA-160 might very well be your best bet.