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Benchmark HPA4

Headphone & Line Amplifier By Dave Clarke
Published August 2022

Benchmark HPA4

If you’ve spent money on serious headphones for critical listening, could it be worth investing just as heavily in your headphone amp?

If you use relatively inexpensive headphones (even professional models such as Sennheiser’s HD 25s, for example), or use your headphones only to check stereo imaging occasionally, or to listen whilst tracking to make sure the performance went down well and that there were no unexpected, untoward noises or headphone bleed, you’ll be fine using the headphone amp built into your mixer or audio interface. But if you’ve invested in a great pair of cans and plan to use them for critical listening, so that you can really get into the nitty gritty of your mixes and masters, it’s worth considering what a decent headphone amp could do for your setup.

It’s worth me pointing out that this product category is aimed at both the pro‑audio and the hi‑fi audiophile sectors, so you do have to watch out for snake oil, but there are plenty of capable amps out there, and I’ve used quite a few in my time. SPL, for example, have good models to suit a range of budgets, and I’ve enjoyed units made by Violectric (a sister brand of Lake People) and Manley too.


Benchmark Media Systems sell to the hi‑fi sector but they’re well established in the pro‑audio sector too, and are known for their unusually high standard of engineering. I recently bought their HPA4, which is identical to their LA4 Line Amp except that it adds a hiqh‑quality headphone amp. Its signal path is entirely analogue, but you can pair it with a Benchmark DAC if you wish; the optional remote control can operate both devices so it’s a seamless partnership.

The HPA4 is available in a choice of silver or black finishes and in two configurations: there’s a 2U 19‑inch rackmount version and a table‑top version. The latter is a little less than a half‑rack space wide and, with its feet, just over 2U high. As well as having a wider faceplate, the rackmount version includes heatsinks to the left and right of the chassis, so it can ‘breathe’ in an enclosed environment (there’s a meaty PSU inside). Whichever version you prefer, the build quality is unassailable: this is a well‑manufactured and nicely designed piece of studio art that exudes quality in an understated manner.

On the front panel are two separate headphone outputs, one being a traditional quarter‑inch TRS jack and the other a 4‑pin XLR, and both are driven from the same (single‑sided) amplifiers. Although 4‑pin XLR connectors are usually associated with ‘balanced’ headphones, that’s not the case here; only the positive sides of the headphone connections are actively driven. Instead, Benchmark use the 4‑pin XLR simply to separate the ground returns from each earpiece (in suitably wired headphones). This provides a better‑quality connection and avoids potential distortion and crosstalk associated with the combined ground return...

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