The lowly headphone amplifier has come a long way. That ¼" jack on the front panels of a few preamps used to be an afterthought—a cheap op-amp circuit thrown in for convenience. But some of today’s standalone dedicated headphone amps boast the same level of design and build-quality as any other high-end component.
The new Neo 430HA from Moon by Simaudio is a prime example. This $3500 headphone amp sports many of the same technologies and circuits found in the company’s other outstanding products. In fact, the 430HA is a distillation of that company’s core circuit designs, which have proven themselves over many years.
The 430HA also exemplifies the increasingly rich feature set of headphone amplifiers. The Canadian-built product has one balanced and two unbalanced pairs of inputs, and balanced and unbalanced headphone jacks. The balanced headphone outputs appear on a four-pin XLR as well as dual three-pin XLR. The unbalanced output is provided on the familiar ¼" TRS (tip, ring, sleeve) jack. A sliding door conceals the three XLR jacks. A fourth input, this one on the front panel, is an 1/8" jack marked “Media Player” to accommodate a portable-audio device. Two line-level outputs are also provided, one fixed and one variable, allowing the 430HA to function as a preamplifier. This feature is particularly useful if you choose the optional DAC ($800), turning the 430HA into the central hub of your system. Digital inputs include two SPDIF, and one each USB and TosLink. The USB input can accommodate PCM rates up to 384kHz/24-bit as well as quad-rate DSD.
The front-panel display indicates the selected input and the volume level. When fitted with the optional DAC, the display can also show the incoming sample rate and which digital input is selected. Front-panel buttons include standby, gain (14dB or 20dB), input select, mute, and “Xfeed.” This latter button engages a circuit that adds a little bit of the left channel to the right channel, and vice versa. Such a “crossfeed” circuit ameliorates the impression of hearing images inside your head, rather than projected in front of you. The penalty is a slight loss of transparency and resolution. Some listeners find the crossfeed effect disconcerting, while others wouldn’t listen without it. Many of these front-panel controls are duplicated on the supplied remote control. The 430HA’s casework isn’t quite as lavish as that of Moon by Simaudio’s top preamps and DACs, but it’s still excellent.
The 430HA drove three headphones for this review, the PSB M4U 2 ($399), Grado SR-80 ($99), and Audeze LCD-X ($1695), the latter in balanced mode. As I’ve spent a lot of hours with an Astell&Kern AK100, PSB M4U2 headphones, and an $800 portable headphone amplifier, it made sense to start by listening to the AK100 and PSBs, substituting the 430HA for my known headphone amp. Granted, the Moon is more than four times the price, but it would nonetheless put the 430HA’s performance into perspective.
To say that the 430HA improved the sound would be a colossal understatement. I was shocked by how much better the PSB headphones sounded in every sonic criterion when driven by the 430HA. With the Moon powering the ’phones, clarity and transparency increased, revealing much more detail. Instrumental lines that had been only hinted at previously were now fully fleshed out, their musical contribution now readily apparent. Fine detail was also better conveyed, particularly in the treble. The 430HA was simultaneously more open and more highly resolved in the top end, but also smoother and more relaxed. Instrumental timbres took on added richness, completely free of grain and edge. Vocals had a silky liquidity that was particularly appealing.
The 430HA’s rendering of bass was spectacularly great, going much lower in the very bottom end and revealing more tonal and dynamic nuances in the bass and midbass. On Jeff Beck’s Performing This Week...Live at Ronnie Scott’s, Vinnie Colaiuta’s big kickdrum that serves as this music’s rhythmic anchor was conveyed with an almost physical sense of impact. Through my previous headphone amp, the kickdrum sounded like a pencil on an oatmeal container by comparison. The sound quality of headphones, particularly their dynamics and bass, is largely dependent on the amplifier driving them. If you think freestanding loudspeakers sound different with different power amplifiers, headphones exhibit an order of magnitude more sound-quality variability.