The problem is that high-sensitivity ‘phones tend to be exceedingly revealing of even trace amounts of noise that may be present. This is where it would be nice if the EF-6 offered (as does Burson’s Soloist) a third low-gain setting that could help keep noise floors in check. This is not to imply that the EF-6 is noisy, because that’s certainly not. It’s just that having a third, lower gain setting could potentially help the amp better manage whatever noise it does produce in those cases where the EF-6 will be used to drive hyper-revealing, high-sensitivity ‘phones.
But please don’t misread us or give too much weight to our discussion of drawbacks, since all of them a relatively minor. The fact is that when looking for an amp that offers effortless reserves of power, considerable sonic refinement, and the elusive and desirable quality of musical naturalism, the EF-6 stands as a wonderfully engaging solution that is quite reasonably priced for the power and sound quality on offer.
For a tour de force show of many of the things the EF-6 does well try playing “Feeling of Jazz” from the Winton Marsalis Quartet’s The Magic Hour [Blue Note], with the EF-6 driving HiFiMAN’s own HE-6 planar magnetic headphones. This is a deceptively demanding track that features deep, powerful, and subtly modulated acoustic bass grooves supplied by Carlos Henriquez; delicate and almost lavishly detailed cymbal work from Ali Jackson; soulful and at times intensely modulated or inflected vocals from Dianne Reeves; and some downright spectacular horn solos from Winton Marsalis—including a few passages where he makes expert use of a wah-wah mute to almost literally make his trumpet “talk.” In short, there are a lot of distinct sound signatures vying for the listener’s attention, all them harder to reproduce than you might at first expect. Through many amps that attempt to drive the HE-6 ‘phones, the sheer sonic workload proves daunting, so that the track winds of sounding brittle, overwrought, or dynamically confused (especially when Reeves sings at full voice, or when Marsalis put the pedal to the metal with his trumpet). But when you leave the driving to the EF-6 you get an altogether different and better outcome. Every drop of hoped-for delicacy and detail makes itself felt, without any hints of discontinuity or sonic confusion when powerfully expressive moments come along.