HPm at Sound On Sound magazine

“There are countless 500-series mic preamps, equalisers, dynamics processors, reverbs, and even delays, bitcrushers and A-D converters on offer, but I can’t recall seeing any headphone amplifier 500-series modules before now.”

“This double-width, dual-output headphone amp is based closely on the company’s well- established Phonitor range of products, and it includes the comprehensive cross-feed matrix facilities that are such a big part of the other models in the range.”

“The front panel is classic SPL, painted black with grey strips to identify each control section and clear white lettering. The two headphone output sockets are sensibly located at the bottom of the unit, each with an individual volume control. At the very top of the unit are a couple of toggle switches, with one selecting mono or stereo listening modes, or mute, while the second flips the polarity of the left or right channel. Sensibly, this polarity flip comes before the mono sum, so it’s possible to audition the stereo- difference (Sides) signal, if required, which is a very handy facility and one rarely found on headphone amps.”

“I bolted the HPm into a standard API Lunchbox rack, and used it to drive various headphones …with impedances ranging from 300? down to 24?. There was more than enough volume for them all, with a very clean and transparent signal, plenty of drive for the low end, and this was complemented with an open and airy top end.”

“Although several manufacturers include variations on the cross-feed idea, SPL’s implementation takes the concept further than most and offers rather more customisation … I’ve been quite underwhelmed with other cross-feed systems, but I could fine-tune SPL’s version to deliver a genuinely useful representation of loudspeaker listening that really works for my ears!”

“At around £450 in the UK the SPL HPm isn’t a cheap headphone amplifier, but it is a very well designed one with genuinely useful features and facilities, and excellent sound quality. Moreover, it represents a very welcome addition to the 500-series module system.”

You can find the complete review online or in the edition 11/17 of Sound on Sound magazine.