HPA4 - "The best sounding headphone amp I've heard"
"For the first time in my audio life I can pin my ear to each speaker driver and hear absolutely no sound coming from the speakers in a quiet room with the system volume control at any position from minimum to maximum with no source material playing."
"I find that lowering the background noise paints the music on as black a canvas as possible and thus seems to bring out realistic low-level detail in recordings."
"The Benchmark HPA4 is the best sounding line amplifier I've yet heard. It's innovative approach to controlling system volume/SPL results in what for me is a uniquely transparent-to-source experience."
"It is also the best sounding headphone amp I've heard, both for very-insensitive, hard-to-drive phones and those sensitive enough to easily be used directly from a smart phone."
"The HPA4 truly stands apart in terms of measured and subjectively low background noise and distortion when driving either loudspeakers or headphones."
- tmallin, moderator of Tom's Corner, whatsbestforum.com