HPA4 Review - Tom Fine, Tape Op

"When the folks at Benchmark suggested a review of their HPA4 for Tape Op, my first reaction was, “Isn’t this aimed more at the audiophile market?” Benchmark’s Rory Rall replied that I should consider its use as a reference-grade monitor controller, with a world-class headphone amp built-in. He recommended I pair it with my Benchmark DAC3 B digital-analog converter and use it to drive my Benchmark AHB2 [Tape Op #111] power amp."

Four Years Experience with the AHB2

"When I previously reviewed the Benchmark AHB2, I described it as being as close to a straight wire with gain as I’ve ever heard – “a silent transmitter of musical energy.” I stand by that description after four years of living and listening to it."

"With the DAC3 B and HPA4 ahead of it, the whole signal chain runs silently and transparently."

The HPA4 Allows the DAC to Run Wide Open

"The HPA4 is built on the idea of avoiding any sort of bit-stripping volume control in the digital realm. So a full-output DAC sends it line-level audio."

"Inside the HPA4 is a precision relay-controlled analog attenuator, with exact channel-to-channel matching and a measurable/repeatable gain or attenuation (expressed in dB on the large color touch-screen front panel display). The volume knob is a 256-step precision encoder, driving relays that engage resistors, in 0.5 dB steps."

"You can memory-set a gain level for each input, so for instance, if you wanted to compare an analog source to a digital transfer, you can precisely level-match. Or (like I often do) measure an original LP release against a digital remaster. Or set your mixer’s output with what’s coming out of your digital rig. The possibilities are limited only by your line-level sources and the HPA4’s four inputs."

Headphone Amplifier

"Finally, in what may be a case of “burying the lede,” allow me to rave about the HPA4’s built-in headphone amp. Designed using similar technology as the AHB2 and licensed from THX (Benchmark calls it the THX-888 Amplifier), this is the cleanest, quietest, most neutral headphone amp I’ve ever heard."

Headphone Output Power

"The HPA4 has no trouble playing music dynamically and precisely through any headphones I own."

"I don’t turn the HPA4 any louder than -30 dB, and lower than that for rock music. Putting it in numbers, the THX-888 headphone amp is capable of peak-to-peak voltage swings of 25V and an output of 1.5 amps. It puts out 6 watts into 16 ohms! This should give you the idea that this thing will drive any low-efficiency cans you want to plug in."

The Price

"For all this silence and neutrality you have to pay a pretty penny, but is it worth it? As with all pieces of your system, it depends. For a precision monitoring setup for mastering, detailed mixing situations, or even a top-shelf listening system, you’ll have to look hard (and maybe spend more) to get this close to the fabled “straight wire with gain” sound."

Conclusion

"I can’t think of anything else that will get you closer to the sound coming out of your sources. Combined with Benchmark’s DAC and power amp with excellent speakers and headphones plugged in, this is quite the monitoring chain."

"When playing music you love, it will fire all the pleasure synapses."

- Tom Fine, Tape Op

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