Intro
Contents
Sylvester Stallone in the first edition of Rocky: “If you wanna have a good time, you need a good watch”. We’re pretty sure he would aso agree with: “If you wanna have a good headphone, you need a good amp”. In many headphone tests, we can confirm this statement wholeheartedly. A good headphone really starts to sing when there is a match with the amplifier. And Benchmark claims that their amplifier technology ensures that there’s always a match. So, we put the Benchmark HPA4 headphone amplifier on our test benches.
It has been some time since we had the Benchmark AHB2 power amplifier in the studio. Nevertheless, the performance of this little powerhouse is still razor-sharp in our memory! We were working on a multitest high end loudspeaker at the time and one of these had a mid-driver that didn’t work. We only noticed this when we connected an amplifier other than the Benchmark. The correction loops between amplifier and speaker were that fast and good that we did not immediately hear that something was wrong with the driver. The Benchmark power amplifier corrected the shortcoming very effectively!
Benchmark
Benchmark was founded in 1983 by Allen H. Burdick (in Texas, later moving to Syracuse, New York).  John Siau joined the company in the ’90’s. The initial focus was on providing equipment for television studios in the US. But also a bit on the home audio market. In 2019 Benchmark is making products that are aimed at the professional, recording studio, and home audio markets.
We already tested two DAC/headphone amplifiers, the DAC-2 and DAC-3 and were also very pleased with these devices. Benchmarks so called Application Notes are very useful to for those who want to dive deeper into any topic on audio; the background articles by John Siau do not necessarily focus on their own equipment. Benchmark is a no nonsense brand. The design is functional and sober. Even model updates are treated by Benchmark as the weather report; “Because the improvements are so small that most won’t hear them, this upgrade can only be seen with measurements”. There aren’t many brands that talk so soberly about their own models!
THX-888
THX, founded by George Lucas in 1982 (after The Empire Strikes Back) is mainly known in the film industry. The organisation wants to take film and sound to a higher level and is doing so by means of certification, research and education. This overview of the different logo’s and bioscope trailers of THX shows clearly what the ambitions of THX are. Benchmark worked for the AHB2 power amplifier and now also for the HPA4 headphone amplifier closely with THX. THXAAA and THX-888 (for headphones or personal audio) are techniques in which continuous feedback loops between amplifier and reproducer should provide ultra-low distortion and an ultra-low noise floor. Yeah, we hear you say that’s what every amplifier manufacturer claims. That’s right, but Benchmark has two amplifiers on board for this purpose: a feed forward amplifier that continuously measures the signals to and from the viewer and provides a correction signal. This is passed on (with a high gain) to the output stage, which has a low gain. Voilà : goodbye distortion (because of the feedback) and down with that noise floor (because of the low gain of the power amplifier).
This technique is the combination of the AHB2 power amplifier with the HPA4 a true feast, at least according to Benchmark. These devices are tuned to each other and can perform optimally due to the aforementioned techniques (high output/low gain). For this review we (unfortunately) only tested the HPA4.
