Cayin has gained a strong reputation in the HiFi community for creating amps and audio players that look incredible – and sound as good as they look. Between high-end DAPs like the N8ii and their tube amplifiers, they’re delivering offerings that are highly competitive with the biggest brands in the industry. Priced at $7500, the Soul 170HA is their latest desktop tube amp. Can it deliver the power and refinement that matches the price – and the competition in the endgame headphone amp space?
Top Level Info
- A massive tube headphone amp, with massive power
- Impressive build and luxurious design
- Loads of features which allow you to adjust the tuning and output to match your headphones and preferences, with the capability to effectively drive any conventional headphones
- NOTE: Soul 170HA has the capability to drive both bookshelf speakers and headphones, but we were only able to test the headphone capabilities of the amp for this review.
Build and Design
Right from the start, Soul impresses with a classic design featuring black aluminum, wood trim, and brass accents. The switches have firm action and a satisfying click and the large central volume knob has a smooth feel and just the right amount of resistance. The unit comes in two pieces, which are connected with the provided umbilical cords: the amp itself and the power supply. Put together, Soul weighs close 100 pounds and takes up quite a bit of desk space. You also have the option of using the unit with the tube protector on or off, depending on your preference for the aesthetics or whether or not you’re concerned about accidentally hitting the tubes.
Soul is a combo headphone and speaker amp sporting a set of banana outputs on the back for speakers. The max speaker output is 18W, so this is more envisioned as a desktop system for bookshelf speakers. For headphones, it has 6.3mm, 4.4mm and 4-pin XLR outputs, which are controlled via a switch so only one output can be active at a time. For inputs, you have XLR and RCA. Soul is equally comfortable as part of a modern digital system connected to a DAC and Streamer, as it is running with a classic, vintage style turntable system connected via a phono preamp.
For tubes, Soul uses two TUNG-SOL KT170 for the output stage, two JJ 6SN7 driver tubes, and two JJ GZ34S rectifier tubes. The driver and rectifier tubes can be swapped out with appropriate alternatives, but the KT170 output tubes should not be swapped out by the end user. When swapping tubes, Soul features an auto-bias circuit design, which eliminates the need for manually setting the bias for tubes.
Using Soul HA-170
While tube amps are often simpler in their feature sets, Soul gives you a number of options for tuning your sound. First off are the Ultralinear and Triode modes. Ultralinear provides the highest output (up to 17W at 8ohm), lowest distortion, and most reference type of sound. Triode gives you more of the classic tube warmth, with a lower maximum output (11W at 8ohm), and slightly higher distortion. You can also choose between Dynamic and Soft timbre, which basically does exactly what you expect. Soft offers a slightly more relaxed sound and can take the edge of off brighter headphones. Dynamic gives you a tighter, harder hitting response.
There’s also the ability to adjust for high, medium, and low impedance. The impedance adjustment is different from a traditional gain control as rather than simply increasing the output, it’s also changing the output impedance of the amplifier. This means that even with very hard to drive planar magnetic headphones, you’ll likely want to stick with medium impedance, which is rated for 65-250ohms, as headphones like Susvara (60ohm), and even the Modhouse Tungsten (155ohm) need the extra power, but, don’t exceed the 250ohms recommended impedance.
All of the functions are handled by a series of switches on the front of the unit. You can switch any combination of Headphone/Speaker, Ultralinear/Triode, Soft/Dynamic, High/Mid/Low Impedance, and 6.3mm/4.4mm/XLR Output.
Sound
Cayin Soul 170HA presents a highly natural, clean, spacious sound. And with up to 17W and the impedance adjustments, there’s not a conventional headphone out there that Soul can’t handle. On top of conventional headphones, Soul’s low noise and low impedance output option make it possibly the best full sized tube amp out there to use with IEMs.
While the Triode/Ultralinear Tube Mode and Soft/Dynamic Timbre options offer some tonal range, there isn’t a huge difference between its most neutral setting, Ultralinear + Dynamic, and the warmest, Triode + Soft. No matter what, you’re getting intricate details, a massive soundstage, with weighty, holographic imaging, and a natural, lifelike presentation.
The interactions with different modes are key to balancing the pairings with different headphones. Triode mode can soften shouty vocals, while Soft timbre will soften some instances of headphones with brighter treble like the HIFIMAN Arya Organic. Dynamic timbre can bring out more detail and dynamics in headphones that sound veiled or hav warmer tunings like the Final D7000. For the hardest to drive headphones, the extra power of Ultralinear mode is going to be the best option, though the maximum of 11W that you get from Triode mode will be sufficient in most cases.
While pairing with a world-class DAC like the dCS Lina provided the best results, Soul shined with just about any source that we plugged into it. From inexpensive DACs like the HIFIMAN EF499 to using the line out jack on an iBasso DX240, Soul seems to elevate whatever input it provided to the next level.
Comparison: Feliks Envy, Mass Kobo 465-044
If you’re in the market for an 17W headphone amp, there’s a good chance that you’re looking to power top-end flagship headphones with it. The HIFIMAN Susvara and Unveiled are two which require that high level of power to get the best performance, while others like the Audeze LCD-5 or Meze Empyrean 2 don’t need a ton of power, but respond very well to it nonetheless. Feliks’ flagship Envy ($7995 as tested) is another tube option, while the Mass Kobo 465-044 ($14999) represents an even pricier option.
Envy and Soul share some characteristics as powerful, reference tube amps with impressive build and craftsmanship to accompany the exquisite sound. The Mass Kobo has a simple metal chassis, but still an impressive build. Soul is the most powerful of the three with it’s maximum of 17W, while Envy comes in at 8W, and Mass Kobo lists the output at 3.8W + 3.8W, but it’s been independently measured at about 4.5W.
In terms of sound, all three are excellent with a wide range of headphones, though I’d give Soul the best marks for use with IEMs. Envy is the warmest sounding of the three, with more color to its sound. The Mass Kobo has an immediacy to its power delivery that Soul and Envy can’t quite match. Even with less wattage, the power and slam Mass Kobo delivers with the HIFIMAN Susvara is unmatched. Soul is close, and while the Mass Kobo offers pure power and dynamics, it doesn’t match the musicality of Envy and Soul. The LCD-5 is a good example of that difference, where Mass Kobo enhances the dynamics, but leaves it sounding a little colder, while Soul and Envy still present excellent dynamics, but lend it more musicality than Mass Kobo.
As a single purpose Susvara (or other highly hard to drive headphones) amp, the Mass Kobo is the best choice, and if you’re looking for the most lush, musical sound of the three, Envy is the best option. Soul stands out as the best all around amp which comes close to Mass Kobo’s dynamics, offers a taste of Envy’s musicality, and provides the most options for crafting your sound.
The Bottom Line
Cayin Soul HA-170 is a lot to take in. Between the size and the price, it won’t be the tube amp for everyone, but if you’re in the market for something that can drive anything from the most sensitive IEMs to the hardest to drive over-ears – and has the tools to adjust the sound to match not only the power, but offer shifts in tonality match the headphones in your collection, then Soul might be it: the ultimate tube headphone amp.
