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Compared to most full-size—not extruded portable—competitors with their various takes on bent sheet metal, the panels Burson uses are far more substantial and heavier. How exactly their tank casing doubles as total heatsink isn't immediately clear. The six transistors bolt to their own mini chimney extrusions which themselves bolt to the circuit board. Tight thermal coupling would have to come from concealed heat-conductive stand-offs beneath the board. Even so, after four hours of operation and quite unlike the class A KingRex HeadQuarters which gets noticeably warm, the Burson chassis telegraphed no heat dissipation to speak of - perhaps a sign of highly effective global cooling spread out over a large surface? Parked atop the HA-160, the April Music Stello DA100 Signature DAC whose own class A enclosure runs clearly warm to the touch made the point. Though separated by the Stello's rubber footers, the whole Burson case beneath got uniformly warm to wick away some of the DAC's own heat.

As the photo shows, the panels are actually lipped extrusions and bolted together via metal L brackets like picture channel frames. This is far from the cheapest way of doing things and very surprising at the low Oz-direct prices.

The HA-160 motherboard integrates Burson's various discrete modules on one shared platform.

Here are the NPN and PNP output transistors mounted to their vertical heatsinks.

Below is another pair of power supply A1930/C5171 transistors. "They form part of our low-noise power supply network feeding the Class A amplification stage. It uses the same technology as our 2nd generation low noise regulator to the right*." Below right, we see one half of the dual-mono stepped attenuator assembly which places a single resistor per channel in the signal path regardless of volume.

* "Each Burson LNR is constructed from more than 17 components. Those include 8 transistors, top-quality Dale resistors and Evox MKP caps matched with a heatsink for bulletproof stability."

Despite Burson's custom-tailored attenuation taper, the Raysonic Audio CD 228's high 4.7V max output and efficient audio-technica 'Raffinato' W5000s caused SPLs outside the comfort zone after three clicks already (April Music's Stello DA100 over Grado's PS-1000s meanwhile sat at six clicks or 10:30). On the first combo, step N°1 on the dial jumped from mute to significant and got into the thick of things right off. Unlike wiper pots, discrete precision resistors offer perfect channel tracking even at the very lowest setting. Listening at the first step causes no sonic compromises. It's simply a bit impractical and impacts user-friendliness with such sources and headphones. Team Burson might want to revisit their resistor ratings below 10:30 and delay the ramp-up for more useful steps on their volume control.

While picking nits, I encountered an immediate ground loop which none of my four other headphone amps ever did with the Raysonic. A cheater plug rectified this instantly but more convenient would have been a ground-lift switch. Ditto a frontal rather than rear-mounted power mains rocker. No ground loop occurred with the affordable 2-box Stello source I inserted next.