Cayin Soul-170HA headphone-speaker amplifier
Among the longer-established Chinese audio product vendors is Cayin, a name that many readers will recognise for combining serious audio engineering expertise with the often typically low retail prices common to products from the region.
The company’s new Soul-170HA headphone-speaker amplifier will make value-hounds go weak at the knees at the sheer amount of product on offer for the £6,899 RRP. Its two-box form factor comes in at over 40 kg and its physical dimensions dominate the kit table with a combined height of getting on for half a metre. If we want to call the Soiul-170HA a desk-top headphone amplifier, we’re going to need a bigger desk.
Get up close though, and it becomes clear that the Cayin’s new amplifier is about more than weight and size. Leave aside its hulking, almost steam-punk appearance, the Soul-170HA is beautifully executed. Flawless matte and high-gloss black metal surfaces are combined with nicely tactile gold-coloured switch toggles, a gold-accented rotary volume controller, a funky VU meter, and walnut side cheeks on both chassis. Oh, and there are glowing tubes. Six of them.
It is a visual feast to behold. But not in a completely over-the-top way; Cayin in its three decades of operation has calmed down somewhat from the earlier days and is now using a design language that reassures buyers they own a distinctive item, but is not so visually loud as to cross the line into tasteless bling.
Electronically, the Soul-170HA is a genuinely dual-purpose device, able to drive all manner of headphones – IEMs too – to a high standard, as well as loudspeakers. Given the fact that it’s Class A, using single-ended triodes for the output gain, and has a maximum output of 18 Watts, those speakers are going to have to be from the efficient end of the spectrum – say above 90dB – in order for the results to be satisfactory.
That dual-purpose designation is worthy of a little context setting. There are many integrated amplifiers that sport headphone sockets on their front panels, and in a sense, they are dual-purpose too. However, with very few exceptions – Enleum’s fabulous AMP-23R is one – none of them can be taken seriously for exacting head-fi usage; their headphone gain stages are an after-thought, too weak and poorly executed, suitable only for occasional monitoring, not extended listening through revealing headphones. What makes the Soul-170HA (and the Enleum AMP-23R) different is that both of them will drive speakers and the most demanding of high-end headphones to a high standard.
Despite its sonic excellence, there are buyers for whom the solid-state Enleum just won’t do. For them it has to be tubes. These are Cayin’s target with the Soul-170HA and the company has given us a clue to exactly what type of tubes in the product name. The drivers are the venerable 6SN7, the rectifiers the well-tried GZ34S, but the output tubes are KT170 tetrodes, newest and most powerful member of the KT series of tubes.
If we take a look at Cayin’s website we can see for ourselves just how seriously the company’s audio designers took their role when developing the Soul-170HA. Its power output, component quality, transformer cores and windings, its circuit topology, its meticulous point to point wiring and the already noted external build quality; all telegraph that this is an amplifier crafted to go head-to-head with other so-called end-game HPAs, but can also drive efficient speakers to a high standard too.
Can can
I connected the Soul-170HA via balanced interconnects to the household’s reference line controller, an icOn5 Balanced, which did switching and attenuation duties for the digital and analogue sources. Once the Soul-170HP had warmed up – and it does get extremely warm, pulling some 200 Watts from the wall socket and radiating most of it into the room from those glowing tubes – I lined up three different headphones in preparation for listening; Audeze LCD 5, HiFiMan Susvara and Sennheiser HD650.
Cayin has endowed the Soul-170HA with the ability to drive headphones with widely differing Voltage and current requirements. The amplifier’s output is switchable on the fly between low, middling and high impedance via one of the two nicely weighted, gold-coloured toggle switches on the front panel. If we are in any doubt, we can click back and forth between the three settings and decide for ourselves which one sounds best. The user-manual doesn’t lie, though, and, as it suggested, the 14 Ohm LCD5 sounded best on the low impedance setting, the 60 Ohm Susvara best on the middling setting and the 300 Ohm (nominal) HD650 on the high setting.
The second front-panel switch controls amplifier output to the three adjacent alternative front-panel sockets, a 4-pin XLR, a 6.5mm jack and a 4.4mm Pentaconn. Which of those we opt to use results in a different maximum power output. The 6.5 and 4-pin sockets give a top of 17 and 18 Watts respectively while the 4.4 pentaconn is throttled back for use with IEMs and gives a maximum of 4 Watts.
On the slanted top surface of the Soul-170HA, arranged in a row underneath the round VU meter, are four further switches. One allows RCA or XLR inputs to be selected. One switches amplifier output between the rear-panel speaker terminals and the front-panel headphone sockets. A third allows the output to be switched between ultra-linear and triode mode, while the fourth also has a notable effect on sound quality by allowing a choice between what Cayin labels as dynamic and soft timbres. I approached this potentially confusing set of sonic options with some suspicion, but after a week or so of use ended up appreciating the unusual degree of flexibility and customisation that it enables.
Sound quality
The review sample Soul-170HA drove all three of the reference headphones to a high standard, exhibiting, particularly in triode mode, the satisfying midrange lushness and sweet detail that we might expect from such an amplifier. Switching to the ultra-linear setting brought about a marked change in the presentation, deepening and tightening up the low-end and extending the top end to the point where, if blindfolded, we might almost, but not quite, wonder if we are listening to transistors not tubes.
Note, in the last paragraph the use of the word ‘almost.’ To be clear, despite the qualities described above, this is still an amplifier with a distinctive sonic aesthetic, different from that of its solid-state alternatives which might be generalised as offering tighter, more neutral presentations.
That should not be read as an expression of disapproval. Far from it. What the Soul-170HA does, it does very well, and there are many potential buyers for whom the amplifier’s sonic imprint is just the ticket. As I like to remind readers from time to time, it was Nelson Pass who gently chided those who take themselves and the concept of ‘correct sound’ too seriously by observing that “This is the entertainment industry, after all.”
The Soul-170HA was not the first headphone amplifier to leave me with the feeling that of the household’s three reference headphones the Susvara is the superior listen. People get quite excited about the ‘hard to drive’ Susvara, but while it’s true it does like more current than most but not all of the alternatives, the reality is – and I can say this with some confidence since the Cayin was the 11th headphone amplifier through my hands within the last twelve months – HiFiMan’s flagship headphone actually works well with a wider range of amplifiers than the legend might suggest.
With the Soul-170HA on its mid-impedance and ultra-linear settings, the sonic results were among the best I have heard via the Susvara, with powerful and textured low-end, a detailed yet liquid midrange, a very thick slice of top-end air and extension, and a pleasing degree of spatial expansiveness and definition.
I connected my PMC MB2se reference speakers to the Soul-170HA’s rear panel terminals and spent an entertaining afternoon reminding myself how tube-derived Watts always sound louder than solid state ones. The PMCs are a claimed 90dB efficient, and while results with more sensitive alternatives would almost certainly sound better still, I actually really enjoyed the sound the Cayin produced. It reminded me of pleasant times past spent with tube amplification produced by the Korean company Allnic, a comparison that Cayin should be happy to read.
Back to headphones though. To a degree, how we view the Soul-170HA is going to depend on the genres of music we like to listen to. Those whose recorded diet revolves heavily around bass-heavy material; for whom subterranean grunt is the primary definer of sonic value, will likely approve. The warbled infra-bass on Limit To Your Love from James Blake’s self-titled 2011 album delivered a skull-massage so vigorous that I was made to laugh out loud.
I’d be less confident in predicting the reaction of listeners who favour classical musical fare. Returning home one evening from a live chamber music recital I hung my coat up and sat down to listen to the Soul-170HA for an hour or so before turning in for the night. With ears freshly re-calibrated to the sound of live acoustic instruments, I played the Lindsays ASV recording of Beethoven’s Op. 130 string quartet, loving the sense of immediacy and intimacy but less keen on what I felt to be the rather richly-fruited low-end imparted by the Cayin.
Conclusion
All of this just goes to illustrate how deeply personal subjective judgements of this nature are, and that my reservations should be seen as just that – personal. The fact is the Cayin Soul-170HA is a seriously well-engineered and well-endowed headphone amplifier able to go toe-to-toe with alternatives at its price point and some way above. Readers will only decide whether they can live with its particular version of sonic truth by auditioning one, and that is something I’d strongly recommend.