Setup

The HPA4 has two balanced (XLR) and two unbalanced (RCA) stereo inputs. Stereo outputs are balanced and unbalanced; there is also a balanced mono channel for a subwoofer, for example. We tested the HPA4 in the studio where the latter function was very useful for mixing and mastering. A stereo signal lead to the monitors and a mono signal to the subwoofer (which has its own active crossover). The Benchmark HPA4 is in fact an analog preamplifier with 4 inputs. On the front we see two headphone jacks; 6.35 mm and a 4-pole XLR. These connections cannot be used at the same time. On the right the volume control and on the left a touchscreen.

We connected the HPA4 to the Weiss DAC2 with streaming module. We played music through a Macbook Pro Retina playback application called Vox. We also used Logic Pro as DAW (digital audio workstation). USB interfaces were a Motu 828es or a Universal Audio Apollo Twin. Headphones used: Hifiman Sundara, Oppo PM-3, Fostex T50RP, Beyerdynamic DT 770 Pro and DT 990 Pro.

L-O-V-E

We have now reached the listening impressions and actually we can be very brief about this. This is one of the best headphone amplifiers and line amplifiers on the market. Nat King Cole’s song L-O-V-E says it all, especially “V is very, very extraordinary”. Actually, our experience was very similar to the AHB2 power amplifier. Whatever headphones we put on, it always sounded good. And not only good, it was neutral and it had punch, depth, character. More sensitive headphones were spared by the HPA4. Where other headphone amplifiers on low impedance headphones could still pose a risk (too much power), the HPA4’s feedforward system ensures a good match in signal level. And if you think that all the headphones on the HPA4 are going to sound the same, that’s not so. On the other hand, the characteristics of the different headphones were easy to distinguish. And in all cases we had the strong suspicion that the Benchmark succeeds in bringing out the best in the relevant headphones.

Operation

The HPA4 comes with an optional remote control. Benchmark has a universal model for all products so if you already have a Benchmark with remote control you don’t have to order another one. The volume knob on the right has 256 steps and for those who go too slow; if you turn the knob faster, the steps also increase. In any case, you can set the desired volume very precisely. It is also nice that you can adjust the line out volume and headphone volume separately. The touchscreen is self-explanatory in its operation. It is nice that you can name the audio inputs yourself and that you can set volume presets per input.