This is the final post in a series of four that looks at (what I call) ‘mainstream high-end’ headphone amplifiers. In the previous three instalments, we covered the Pro-Ject Head Box DS2 B (with its optional power supply), the SparkoS Labs Aries, and the ZMF Pendant.
At US$2499, Cayin’s HA-6A is not actually their flagship offering. That would be the firm’s beastly HA-300: a two-box, ~30kg monster which drives both speakers and headphones with direct-heated triode 300B exuberance. Since the focus here is headphones, and with the HA-6A being newer and arguably more versatile, it seemed the better fit for this roundup.
Weighing in at nearly 20KG, the HA-6A is still an extremely stout amplifier. With crisp industrial design on the outside and classic point-to-point wiring within, the HA-6A makes quite the visual statement – gotta love those big VU meters! Those shielded, top-mounted EI power and output transformers are designed and built in-house. Volume is controlled by a custom high-precision 24-step resistor-based potentiometer. A relatively attractive tube cage is included for safety (music lovers with children are encouraged to make use of it) though it can easily be removed if one has no such worries.
A trio of front panel headphone outputs offers maximum versatility. We get the expected 6.35mm single-ended jack plus a balanced 4-pin XLR, but also the increasingly popular 4.4mm Pentaconn balanced connection. The rear panel is more simplified with just one each of XLR and RCA inputs – this is a dedicated headphone amplifier with no pre-amplifier outputs.
Stock tubes include a pair of Electro-Harmonix 12AU7EH for the input stage plus a set of NOS RCA 22DE4 tubes for power rectification. Driver tubes are a matched pair of Electro-Harmonix EL34EH, but the HA-6A has a trick up its sleeve: the bundled (and also matched) pair of Genelex Gold Lion KT88 tubes, which can be swapped out for an EL34 set (also supplied). Just make sure to set the rear-panel switch to match your tube array of choice. Cayin’s other big trick involves choosing between triode and ultra-linear operation with the push of a button – an option which is exceedingly rare in tube headphone amplifiers. Combine that with low/medium/high output impedance selection, and listeners have multiple options for achieving their ideal sonic presentation – and I haven’t even covered tube rolling yet.
With so many sound profile permutations on board, I can’t possibly cover every option here, but I’ll offer up a few comparisons. My initial baseline (of sorts) was with the stock EL34 tubes, in triode mode, with output impedance set to low. Using that configuration with the Focal Utopia running from an Audio Art HPX-1SE balanced cable gives a wonderfully delicate, smooth presentation, with fleshed-out midrange and a beatific sense of tone which defies easy description. It is simultaneously open and intimate, with superb spatial definition and rock-solid imaging. This configuration is wonderful with “simpler” music such as folk, singer-with-guitar acoustic stuff, solo piano works, jazz trios, string quartets, and other such material, all of which tends to be available from “audiophile” labels with a reputation for exceptional recording/mastering quality.
Hitting the button to activate ultra-linear mode brings more impact at both frequency extremes to push the midrange further back in the mix. Some of that vocal sweetness is gone, traded in for better dynamics and a larger but slightly more diffuse soundstage. This mode seems better suited for what I’d call general-purpose music listening: Chronixx, The New Amsterdams, Crystal Castles, Apathy, and Beverley Knight. It’s closer to the typical solid-state amplifier’s presentation but retains a healthy dose of tube bloom.
Flipping the switch to higher output impedances does nothing good for the Focal Utopia. Bass becomes looser on medium and downright wooly when set to high. Everything from the upper midrage and beyond starts to feel muffled. After trying over a dozen headphones, I ultimately preferred the low setting for nearly all of them, with two exceptions: the 300 Ohm Sennheiser HD800 which sounds best on medium, and the 600 Ohm Beyerdynamic T1 where both medium and high settings have merit. Nonetheless, I appreciate having the option as future headphones models could very well join this list.
Swapping out the EL34 set for the KT88 generally mirrors the changes heard when switching from triode mode to ultra-linear. Running the pair of EL34 tubes places the focus on that seductive midrange, with an overall softer and more intimate feel top to bottom. Meanwhile, the KT88 emphasises bombastic dynamics and loads in superior bass texture, more expansive top-end air, and a more balanced presentation from top to toe. My general impression is that KT88 operation sounds consistently great with a variety of headphones whilst the EL34 is more selective yet quite rewarding when a harmonious match is found.
With all these variables, it’s easy to see how the HA-6A has a little something for everyone. Want a rich, warm sound, dripping with vintage tube charm? Run the EL34s in triode mode, and maybe switch to medium output impedance depending on the headphone in use. Mission accomplished! Prefer a faster, more balanced sound signature with superb extension and plenty of muscle? Swap in the KT88 duo and run them in ultra-linear mode with low output impedance. Done deal! Looking for some combination of both of those extremes? Just mix and match for interesting results. My personal favorite often ended up with KT88 tubes running in triode mode, which gives pleasing solidity tempered by an air of tonal seduction for what I consider a nearly perfect compromise.
As if this wasn’t already complex enough, let’s briefly talk tube rolling. While the bundled Electro-Harmonix glass is not the worst I’ve ever heard, I do hear worthwhile gains when swapping them out, even with new-production tubes. The driver tubes in particular offer the most room for improvement, with offerings from Mullard or JJ bringing noteworthy improvement for around US$50/pair and NOS sets going further still (and priced according to their audible gains). Meaningful upgrades on the 12AU7 bottles begin at around US$25/pair, with excellent sets easily had for around $100/pair. Meanwhile, the bundled Genelex Gold Lion KT88 pair is actually very nice, and isn’t worth replacing without a substantial expenditure. I did not mess with the rectifier tubes as they are not very common and the bundled RCA NOS set is likely already a great match. All this to say the HA-6A can become an even better performer without breaking the bank on ultra-pricey glass.
Downsides? Compared to our Pro-Ject DS2 baseline, the Cayin has a slightly louder noise floor. This varies according to tube array and is never remotely close to what I’d call a “problem”… it just isn’t quite as inky black as the Austrian solid-state option. My main gripe actually has to do with Cayin’s discrete volume control solution. Its 24 steps are insufficient — the increments between each step being a bit larger than I’d like. The sound also comes on fairly strong at lower levels, enough to prove too loud with certain headphone models. I had this same complaint with the big Cayin HA-300 amplifier, and while using a DAC with quality volume control for a bit more trim is a perfectly functional solution, I’d rather have more granular steps on the amplifier.
Aside from that, Cayin’s chameleon-like HA-6A is a superb choice for those wanting maximum sonic versatility in a headphone amplifier. In some cases, I actually prefer it to the bigger/more expensive HA-300 because the HA-6A’s signature can be dialed in for maximum synergy with a particular headphone and source combination. While not at all an inexpensive amplifier, when we factor in the stunning good looks, absurdly sollid build quality, and its numerous sonic presentations, the Cayin HA-6A might actually qualify as something of a bargain. Plenty of folks out there own multiple headphone amplifiers to realise a variety of headphone sound profiles. The HA-6A rolls it all into one device. Brilliant.
Further information: Cayin
For this evaluation, I set up a very high-performance system capable of taking even the best headphone amplifiers to their limits.
The foundation was laid using the Equi=Core 1800 (US$2199) balanced power conditioner and Audio Art power1 ePlus AC cables feeding every component. My transport setup is a bit ridiculous yet totally worth the trouble. It starts with a Euphony Summus (US$2599) music server augmented by a Keces P8 (US$699) ultra-low noise linear power supply. An iFi Gemini 3.0 USB cable splits power and data legs as they travel to a Matrix X SPDIF 2 DDC (US$379) powered by a Wyred4Sound PS-1 linear PSU (US$499). Finally, signals are routed to a Titans Audio Lab Helen (US$1699) for additional jitter/noise reduction, and then off to a Wyred4Sound 10th Anniversary DAC (US$4499) for D-to-A duties. Aside from the iFi USB leash, Audio Art’s e-series cables handle all digital and analog connections.
Headphones run the full gamut from classic Sennheiser HD650 and AKG K701 to modern flagships like HiFiMAN’s Susvara and the Meze Empyrean. The ubiquitous Sennheiser HD800 and Focal Utopia both make appearances, as do lesser-known gems such as the Kennerton Audio Thekk and Audeze LCD-24 Limited Edition. I also didn’t shy away from trying sensitive in-ear monitors ranging from the sensibly-priced Campfire Audio Comet to top-of-the-line 64 Audio A18t customs, and many models in between.