"While you may think that any amp whose quiescent residual noise you cannot hear from your usual listening position is quiet enough, that has not been my subjective experience. This is one reason I'm now a big fan of the Benchmark equipment, including the AHB2 amp. I've been using a pair of them in bridged mono, as well as the Benchmark DAC3 HGC to drive my Harbeth M40.2s for awhile now."
"With this combination of electronics, 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. Most amps produce quiescent noise under such conditions loud enough to be clearly heard at least a foot from a speaker driver, often more like several feet."
"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. While I may not actually hear residual amp noise as hiss/hum/rumble/roar, I more clearly hear the environmental ambient noise captured on the recording if the amp noise is lowered and this increases my perception of hearing the music in its recording venue, as well as my perception that the music is being made by real humans producing little noises like forceful breathing in rhythm, sub-vocalizations, lips parting, risers and chairs creaking, etc."
"For best headphone sound, use the four-pin XLR connector on the front panel of the HPA4, rather than the 1/4" TRS jack on the HPA4 ... the four-pin XLR connector has no chance of producing measurable distortion."
"Expect to hear quite-audible-from-the-listening-seat rapid clicking/chattering when adjusting the volume up or down with either the remote or front-panel volume controls. That's the sound of the HPA4 relays. If your SPL is already moderate or higher, the sound of the music may well cover up the sound of the relays. Just to be clear, this noise is purely mechanical and comes from the HPA4 chassis. There is no electronic clicking noise audible at all through speakers or headphones when the volume is adjusted."
"My reference headphones are the Audeze LCD-4 fitted with an aftermarket "balanced" Moon Audio Silver Dragon cable with a 4-pin XLR connector at the amp end."
"The whole presentation sounds more "solid" with the HPA4 than it did with the 430HA, giving the impression that the amp has a more solid grip on the drivers. The presentation gains a more "out front" aspect, with the presentation seeming significantly more in front of my head than it was before, while having equally wide spread. This is especially true of the NAD Viso HP50 headphones, probably because the subjective frequency response of those phones lacks any depression of the presence range and lower highs whatsoever and especially because of the "RoomFeel" response technology built into those phones."
HPA4-"The Best Sounding Line Amp I've Yet Heard"
"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 (Tom), Moderator of Tom's Corner, WhatsBestForum.com
Note: Above quotes are from a very lengthy and well-written review of the HPA4 by tmallin (Tom) at What's Best Forum. We recommend following the links below and reading Tom's complete review.
LA4 - Receives Stereophile's Highest "Class A" Rating for Preamplifiers
"Benchmark's usual approach to design is to out-spec the competition, and so it is here. Like other Benchmark equipment he has tested, the affordable LA4 challenged the resolution of John Atkinson's test instruments, with'superb'channel separation,'extremely low noise, and virtually no power-supply-related spuriae.'"
"Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered."- John Atkinson
"In his listening room, Kalman Rubinson compared the LA4 to a cable—and couldn't hear any difference. He concludes,'the LA4 is probably the most transparent and revealing audio component I've ever used. It does not seem to leave any fingerprints on the sound.'"
"The DAC3 B is a stripped- down, lower-priced version of the DAC3 HGC, which omits the headphone amplifier, balanced and unbalanced analog inputs, volume, mute, and polarity controls."- Stereophile
"The DAC3 was all about depths, in several respects...I heard deeper into the music."
"All I can say is Wow!"
- John Atkinson
"In a Follow-Up, JCA wrote of using the Benchmark processor with the same company's AHB2 power amp—a combination of high source output voltage and modest amplifier gain that he describes as 'optimal for minimizing noise and distortion' —and reported hearing 'richer and more interesting' reproduction of very subtle details."