DAC / Amp Dongle Matchup

    Audio: Listen to this article.

As I’ve written about before, despite being engrossed in audiophiledom for the past decade or so, I only recently ventured into IEMs. Most of my listening occurs at home, so size and portability rarely factored into my decision-making. However, I belated realized that the diminutive IEM could open up new possibilities for at-home listening. After all, it’s hard to lay down with a pair of full-size over-ear headphones on your head. But it’s pretty darn easy to do so with a pair of IEMs snugly inserted into your ears.

Of course, becoming IEM-pilled has posed its own first-world problems. The Roon Remote app allows me to access my whole collection on my iPad while relaxing anywhere in the house. But particularly in our post-headphone jack era, how was I to know what portable DAC/amp should come between my iPad and my IEMs?

In order to answer that question, I’ve purchased dozens of passive DAC/amp “dongles” and battery-powered DAC/amps over the past few years. I’m going to review these devices in two articles, one covering each category of portable DAC/amp. Measurements of many of these DAC/amps can be found across the interwebs. My reviews, instead, will consist of level-matched subjective evaluations with head-to-head quick switching.

This article will look at some of the dongles available on the market today. This is a non-comprehensive review consisting of six dongles that I’ve kept on hand for one reason or another — usually because nothing about them caused me to quickly cast them aside. With a few exceptions that I’ll explain next, if it’s not in this review, I haven’t heard it. And if I end up accumulating enough new dongles in the near future, I’ll write a second installment to this dongle review.

In the interest of transparency, though, I’ll mention two dongles that I purchased but did not make it into this review because I returned or sold them shortly after receiving them. The first is the Shanling UA5. I had difficulty getting it to connect to my iPad consistently, so I was not able to evaluate its sound. However, I liked the UA5’s build and generally have had good experiences with Shanling products. The second is the Cayin RU6. It’s received a great deal of attention because it’s the rare dongle that utilizes an R2R DAC. Again, this is a beautifully constructed dongle, and I encountered no functional issues. But in terms of resolution, it sounded just a bit low-fi and hazy to my ears. I came to this conclusion based on subjective listening, but I think @Archimago’s subsequent review and measurements offer hints about what I was hearing.

With that out of the way, let’s run down the entrants in this dongle showdown from lowest price to highest:

• Hidizs XO — $79 (Amazon, $99 with 20% coupon)
• NuPrime Hi-mDAC — $75 (NXEars), $139 (Summit Hifi)
• FiiO Jade KA5 — $129 (Amazon)
• Muse HiFi M3 — $149 (HiFiGo)
• Questyle M15 — $211 (Questyle, Audio46)
• iFi Go Bar — $329 (Amazon, Bloom)

Unit-by-Unit Overview

The $79 Hidizs XO is a small rectangular dongle with only two buttons — fittingly, an X and an O. It measures approximately 55 by 24 by 9.5 mm and weighs 14 grams. The otherwise utilitarian metal housing gets more intriguing on the left and right sides, which are chamfered on all four edges and sport a perforated set of LED lights. These tunable LED lights add a bit of gamer flash to the XO. They weren’t a draw for me, but I grew to appreciate them as a fun addition when listening to some tunes on a dark evening. The XO has a USB-C port on one end and both 3.5 mm single-ended and 2.5 mm balanced outputs on the other.

The XO utilizes two ESS Sabre 9218C and is compatible with PCM files up to 32bit/384kHz and DSD files up to 256, as well MQA. Given the competing standards for reporting specs like THD+N, power, etc., I’m simply going to direct you to Hidizs’ website. Suffice it to say, this is a (level-matched) subjective review, and potential buyers concerned about measurements are advised to consult trusted third-party measurements anyhow.

Unsurprisingly at this price, the XO’s packaging and accessories are modest. Only a USB-C to USB-C cable and an USB-C to USB-A adapter are included.

Functionally, the XO was bulletproof in my use with both my USB-C and Lightning-equipped iPads. It kept a consistent connection to my iPad and didn’t evince any worrying quirks. The HiByMusic app allows for access to more advanced features, but the only controls on the dongle itself are accessed using the two buttons. The X button cycles through 15 LED lighting patters, while the O button switches the filters. These were the only controls I used, since I couldn’t figure out how to use the iOS version of the HiByMusic app (though I do understand that the Android version is better). Volume adjustments have to made at the source, since the XO does not have any hardware volume control. But for $79, I was fine with these limited options.

Next up is the NuPrime Hi-mDAC. The Hi-mDAC is an older dongle. Right now, it can be found for a few dollars less than the XO. However, it traditionally costs $139. At 50 by 23 by 12 mm, the Hi-mDAC is very similar in size to the XO, but nearly doubles its weight at 22 grams The metal housing is a bit rougher than the XO’s, with the non-chamfered sides feeling a bit sharp. However, the (literal) mirror inlay on one side is pretty neat. The Hi-mDAC features two volume buttons along its right side, a USB-C port on one end, and a single 3.5 mm single-ended output on the other. Interestingly, it seems the 3.5 mm analog output doubles as an SPDIF output, which means the Hi-mDAC could, in theory, be used as a USB-to-SPDIF converter.

The Hi-mDAC employs Cirrus Logic’s CS43131 chip as both a DAC and headphone amplifier. It can decode PCM up to 32/384 and DSD up to 256. As with the XO, I’ll leave readers to peruse NuPrime’s site for the Hi-mDAC’s claimed specs.

The Hi-mDAC’s packaging is even more spartan the the XO’s, and it includes only a USB-A to USB-C cable.

In terms of functionality, the Hi-mDAC is the… quirkiest dongle under review here. First, while the other dongles all work with iOS devices using a single USB-C to USB-C or Lightening to USB-C cable, the Hi-mDAC requires some variety of Apple Camera Adapter. Second, while the NuPrime site claims the Hi-mDAC features switchable filters, I confirmed via email with the company that this is not the case. Given that selectable filters were part of why I bought the Hi-mDAC, that was a disappointment. Third, I was not able to get the Hi-mDAC to work with any of my computers, even as it worked more-or-less flawlessly with my iPad and a Camera Adapter. As far as I can tell, other owners have successfully used the Hi-mDAC with both Apple and Windows computers. So this may simply be user error on my part. Given my iOS-only use case, I didn’t bother to do much troubleshooting. Fourth, the Hi-mDAC often (perhaps one-third of the time) a loud pop through IEMs upon initial insertion.

Stepping up a bit in price and features, we have FiiO’s $129 Jade KA5 dongle. At 56.5 by 22 by 12 mm, the KA5 is a bit longer than the Hi-mDAC. However, at a scant 19 grams, the KA5 is hardly bulky. Stylistically, the KA5 shares much more in common with the stylish XO than the utilitarian Hi-mDAC. Every edge of the KA5’s anodized aluminum body is angled. The bottom of the unit sports a tempered glass nameplate with a faint honeycomb pattern. The top features the FiiO logo and small OLED screen, again covered in tempered glass. The left side of the KA5 has three buttons: a multifunction button and two volume controls. One end has a USB-C input, while the other has both 3.5 mm single-ended and 4.4 mm balanced outputs. Like the Hi-mDAC, the KA5’s 3.5 mm output can also be used as a SPDIF output.

The KA5 sports dual Cirrus Logic CS43198 DAC chips, providing 32/768 PCM and DSD256 support. Amplification is handled two SG Micro SGM8261 op-amps. According to FiiO, these are situated on a “six-layer immersion-gold PCB.” Impressively, FiiO’s site does not merely list the KA5’s specs but also provides a full suite of measurements.

The KA5’s packaging and accessories are a clear step up from both the XO and Hi-mDAC. It includes short fabric-covered USB-C to USB-C and Lightning to USB-C cables, as well as a USB-A to USB-C adapter.

Using the KA5 is a breeze. The OLED screen displays the volume, gain, filter, and sample rate, among other info, which makes navigating the KA5’s ample settings easy, even with only three buttons. Summarizing all of the KA5’s options isn’t easy. It offers two gain settings, five DAC filters, two volume step options, Class H or Class AB output for the DAC chip, left-right balance, and a de-pop hardware mute, as well as various display preferences. Thankfully, FiiO’s manual is detailed and its FAQ page is even more helpful. (In general, I’ve found FiiO to have one of the clearest websites around.) Android users have the FiiO control app to help them navigate the settings, but it’s not available on iOS. That said, I didn’t have any issues setting the KA5 to my preferences using the its buttons and screen. Most importantly, I never encountered any functional issues with the KA5, regardless of operating system or music app. It just works.

Stepping up $20 in price from the KA5 we have the $149 Muse HiFi M3. The M3’s industrial design is exquisite. Its undulating all-metal body is Apple-meets-Gehry. At its widest points, the M3 measures approximately 58 by 29 by 15.5 mm. Given its all-metal construction, it weighs in at a hefty 54 grams. While the M3’s build is superb, compared to the KA5, its features feel a bit lackluster. The M3 has two volume buttons and one LED light along its flank. Otherwise, it has a USB-C input at one end and both 3.5 mm single-ended and 4.4 mm balanced outputs at the other.

The M3 is based on the ESS’s ES9038Q2M DAC chip and ES9603Q amp chip and supports PCM rates up to 32/384 and DSD up to 256. While Muse does not seem to have an English-language website, its specs can be found on most retail sites.

The M3 comes in a stylish package, which includes short well-made short USB-C to USB-C and Lightning to USB-C cables, plus a USB-A to USB-C adapter.

Using the M3 is straightforward. The volume buttons also allow the user to select between seven filter options, which are indicated by the small LED light. Otherwise, the M3 is simply plug-and-play. Besides an occasional more-than-expected pop when plugging or unplugging IEMs, I encountered no issues with the M3 during months of use.

The next entrant is the $211 Questyle M15, which has been reviewed previously here on Audiophile Style by @gmgraves. Stylistically, the M15 might be my favorite unit under review. The M15 measures approximately 62 by 27 by 12 mm and weighs 28 grams. From a distance, the M15 looks like a rather bland black rectangle. But up close, it’s clear that the unit is machined from a solid piece of aluminum, with every edge perfectly contoured. The top of the unit has glass perfectly inlayed, revealing the M15’s circuit board, which includes two status LEDs. Besides a low/high gain switch on one flank, the M15 has no controls, meaning that — like the Hidizs XO — the M15 lacks a hardware volume control. Otherwise, the M15 features a USB-C input at one end and both 3.5 mm single-ended and 4.4 mm balanced outputs on the other.

For digital-to-analog conversion, the M15 deploy’s ESS’s ES9281AC chip, which can decode up to PCM 32/384 and DSD256. More intriguingly, “The M15 contains two of Questyle’s patented CMA (Current Mode Amplification) SiP modules, for a total of four CMA amp engines. This quadruple drive amplification circuitry gives an outstandingly strong output that can drive almost any headphone. Questyle’s Current Mode Amplifiers are characterized by their small footprint, low voltage operation, and minimal power consumption.” The M15’s impressive specs, including several measurement graphs, can be found on Questyle’s website.

The M15 is solidly packaged. The tab-pulled internal box slips out to reveal the M15 in a molded foam cutout, under which sit the two short cables: a USB-C to USB-C cable and a USB-A to USB-C. Overall the cables seem to be good quality but are just a bit stiff.

I had absolutely no issues using the M15 with any device, including both lightning and USB-C Apple devices. When connecting the M15 to the source via the USB-C input, nothing indicates that the unit is on. However, upon inserting an IEM or headphone cable into either the 3.5 or 4.4 outputs, the M15’s gain indicator LED will glow either green (for low gain) or red (for high gain). Once music is being played from the source, the M15’s data indicator light will glow, too.

The final contender in this dongle showdown is the $329 iFi Go Bar. The Go Bar’s constructed of a two-piece metal case, which feels like an anodized aluminum. Rather than a simple rectangle, the Go Bar features an angled top with a center plateau and two slightly narrower sloping sides. One flank of the Go Bar features its controls: a function button, two volume buttons, and an iEMatch switch. The latter is a built-in version of iFi’s $49 standalone iEMatch, one of my favorite IEM accessories. While the details are a bit complex, the iEMatch alters the output’s level and impedance in order to cut potential hiss and expand the usable volume range with sensitive IEMs. The underside of the Go Bar features nine LEDs alongside various labels, which tell the user about everything from the format sample rate of the audio being played to the gain level to whether XSpace or XBass are enabled. The former is a crossfeed effect, while the latter is a bass boost. One end of the Go Bar features a USB-C input, while the other sports both 3.5 mm single-ended and 4.4 mm balanced outputs. The Go Bar measures approximately 65.5 by 22 and 13 mm at its widest points and weighs 29 grams.

According to iFi, the Go Bar utilizes a “2-bit Cirrus Logic DAC chipset,” which I’ve seen reported as the CS43131 chip. It handles PCM rates up to 32/284, DSD up to 256, DXD, and MQA. The Go Bar’s amplification section is comprised of “a balanced circuit design with symmetrical twin-channel output stage. This reduces noise and crosstalk in the signal path by fully separating the left and right channels.” The Go Bar’s specs are reported on iFi’s website. It’s also been measured by Audiophile Style writer @Archimago.

The Go Bar’s packaging is attractive but perhaps a bit less protective than the M15’s. However, none of the aforementioned dongles can match the Go Bar’s accessories. The Go Bar comes with a gorgeous leather case that reminds me of a pocketknife sheath. The case closes with a magnetic snap. Inside are two compartments: one for the Go Bar itself and one for its cables. Speaking of the cables, iFi generously includes a USB-C to USB-C, a USB-C to Lightning cable, and a USB-C to USB-A adapter. The cables are thick-but-flexible and covered in a gold-colored fabric. They’re the nicest included cables of any of the units under review, followed closely by FiiO’s.

Especially given its large number of features, I found the Go Bar to be incredibly easy to use. The underside LEDs more-or-less obviate the need for a display. I memorized most functions after a quick perusal of iFi’s simple manual, only returning to it for a quick refresher on changing the gain (two options) and DAC filter (four options). After picking my favorite of those, I essentially only touched the side-mounted volume buttons and iEMatch switch. Finally, I had no issue using the Go Bar with any of my sources — Windows, Mac, and iOS (Lightning or USB-C) — or player apps. The Go bar worked flawlessly in all contexts.

Before moving onto the listening, I want to add one more data point. Given that dongles’ primary strength-meets-weakness is their use of the source device’s power, I wanted to see how much amperage each pulled when powering the Moondrop Kato IEMs to 100 dB of white noise. So I pulled out my USB multimeter, and here are the results:

• Hidizs XO — .150
• NuPrime Hi-mDAC — N/A
• FiiO Jade KA5 —.125
• Muse HiFi M3 —.155
• Questyle M15 —.095
• iFi Go Bar —.145

As usual, the Hi-mDAC would not work with my computer, and since the multimeter breaks its connection with my iPad, it didn’t get measured. Otherwise, the results show that the XO, M3, and Go Bar are all in the same ballpark. But given the Go Bar’s overall power advantage, it’s definitely the best of the trio. The two lowest-draw dongles are the KA5, which is about 17 percent more efficient than the previous trio, and the M15, which is a shocking 27 percent more efficient than the original trio.

With that descriptive throat-clearing out of the way, let’s talk about how these dongles sound.

Sonic Showdown

Given that six units are under review, I’m going to employ a head-to-head comparison in the style of my TBVOs. I’ll begin with the two lowest-priced units, with one winner moving on to the next round until only two units are left.

For the audition, I plugged four dongles at a time into my Mac mini. The units were level-matched to within .5 dB using the pair of IEMs or headphones chosen for that listening session, my MiniDSP EARS rig, and Room EQ Wizard. The IEMs or headphones stayed stationary on the EARS while their plug was switched between the dongles. A white noise file generated by REW and played with Roon was routed to each successive dongle while matched the dongles’ levels, using either the dongle’s on-unit volume buttons or Roon’s volume control.

For the transducer in the first-round matchup, I chose the previously reviewed Moondrop Kato IEM. The Kato is one of the best IEMs on the market today. At a $190 with an included case, it’s also just the sort of IEM that folks are likely to pair with the DAC/amp dongles at the lower-end of our price spread.

The first matchup pits the Hidizs XO against the NuPrime Hi-mDAC. For audition tracks, I chose two songs from the hi-resolution version of Van Morrison’s superb collection of unrelease material, The Philosopher’s Stone. With few exceptions, Morrison’s work is expertly recorded. Most of the songs on The Philosopher’s Stone were cut live in the studio with few overdubs, which makes them ideal for evaluating equipment. First up is “The Street Only Knew Your Name.” Moving back-and-forth between the XO and the Hi-mDAC, it’s clear that the latter is the brighter-leaning of the two dongles. Metallic tones from electric guitars to cymbals have more snap and sizzle on the Hi-mDAC. However, this comes at the cost of some edginess, particularly in vocal sibilance. Meanwhile the XO is the warmer of the two units but tends to soften the edges of transients just a bit. That doesn’t seem to translate into overall lower resolution, though. The XO doesn’t provide the final word on resolution when it comes to the shaker in the background of the intro to “The Street Only Knew Your Name” but neither does the Hi-mDAC’s treble tilt seem to give it an edge on such details. In other areas, like soundstage depth, the Hi-mDAC does edge out the XO. Yet the XO seems to convey more subtlety on Van’s vocals and seems to have better low end weight and driver control. Moving on to “John Henry,” which opens with isolated guitar, bass, and drums, the Hi-mDAC does seem to wring a bit more detail out of the recording. However, it’s hard to say whether that’s real or just the effect of its sharper transient edges and brighter tonality.

Turning to the next selection, “King of the Jailhouse” from Aimee Mann’s The Forgotten Arm, the Hi-mDAC’s lead on resolution seems more undeniable. “King of the Jailhouse” features a clever hard-panned mix by Ryan Freeland, where everything but Mann’s vocals are pushed to the left or right. It’s a fantastic choice for the song, and it really tests whether a given piece of equipment can distinguish all of the elements bunched together at the edges of the soundstage. The Hi-mDAC seems to do that better than the XO. The background vocals mixed far right and the mandolin mixed far left, for example, are simply easier to distinguish through the Hi-mDAC. It likewise gives more articulation to the strings on bass guitar, which is a key element in the mix. On the other hand, the XO’s presentation of Mann’s lead vocal feels more lifelike and sounds less sibilant. So it’s actually hard to give the Hi-mDAC a clear win on “King.”

Given my equivocal reaction to the sound of these two dongles, I turned to Haim’s “Falling” from the band’s Days Are Gone debut album as my sonic tiebreaker. As a dense, decidedly modern mix and mastering with lots of elements at both extremes of the sonic spectrum, “Falling” really tests weather gear can handle loud-and-busy tracks. Specifically, I zeroed in on the song’s dense chorus, which can come across as bloated and chaotic on poor equipment. While the Hi-mDAC seemed to have the edge on the more spacious Morrison and Mann cuts, “Falling” clearly favors the XO. The Hi-mDAC’s rendering of “Falling” was simultaneously muddy and sharp, making for an unpleasant listen. Vocal sibilance abounds. Meanwhile, the XO holds the mix together without being too bright or too flabby. While it doesn’t do the best job of separating all of the mix’s overlapping elements, it also doesn’t collapse them together like the Hi-mDAC does.

This level-matched comparison of the Hidizs XO and NuPrime Hi-mDAC reminded me of why I liked the latter when I first purchased it several years ago. It’s the more analytical of the two units under review, and its sonic limitation aren’t very noticeable on recordings with few a modest number of elements in the mix. But the Hi-mDAC’s crisp transients can veer into edginess, particularly when it comes to vocals, and it can’t handle the “Falling” test nearly as well as the XO does. Add in the fact that the Hi-mDAC has abundant functional quirks, and it’s a relatively easy choice to move the XO to the second round.

Now the bare-bones Hidizs XO has to grapple with the pricier and feature-rich FiiO Jade KA5. For those keeping score at home, I settled on high gain, Class H mode, and the linear phase fast-roll-off filter for the KA5. In choosing the first audition track, I decided to switch from Van Morrison to the most adept of Morrison’s progeny with “Anna Begins” from the MFSL CD of the Counting Crows’ August and Everything After. Thanks to T-Bone Burnett’s production and Pat McCarthy and Scott Litt’s mixing, August is easily among the 1990s’ best-sounding albums. My initial impressions with this track were that the XO and KA5 were close. However, closer back-and-forth comparison showed that the FiiO has the undeniable edge. The opening of “Anna Begins” places the drums and bass front-and-center. The XO presents both with excellent heft and is overall a pleasant listen. But the FiiO simply has better control of the Kato’s dynamic driver. Transient attacks are more sharply delineated without being overdrawn, while the snare is placed suitably deep in the soundstage. The XO’s slightly rounded transients, on the other hand, make the hi-hat a bit less realistic and robs the bass of some string articulation. Meanwhile, its shallower staging pulls the snare too close, causing it to compete with Adam Duritz’s vocals later in the track. One other notable quirk is that, on the song’s slow fadeout, the XO introduces some static at moment of full fadeout, which may have to do with how the unit deals with muting. This issue wasn’t present on the KA5, though.

Turning to Mann’s “King of the Jailhouse,” I focused on one of the most notable elements of Freeland’s superb mix. While Paul Bryan’s anchoring bass is mixed far left, the string noise from the bass is panned far right. The KA5 not only captured the initial burble of the bass on the left better but it also creates the requisite space around the string noise in the right channel to separate it from the drums. Speaking of the drums, the KA5 conveys the extremely soft, subtle fills between beats in the intro better than the XO’s somewhat blurry rendering. Fast forwarding to a busier moment in the mix, I focused on the “So they packed up their troubles in an old Cadillac” line. On good equipment, Mann’s vocals should have a hint of sibilance and plenty of space, while the electric guitar in the right channel should be separable from the other hard-right elements. On both counts, the FiiO easily bests the XO. For good measure, I also returned to Haim’s “Falling.” Again, I looked to the busy section that begins near the 1:40 mark. While the KA5 was already in the lead, “Falling” sealed the deal. The FiiO does a better job keeping both the Haim sisters’ vocals and the ascending ‘80s-style keyboard in the right channel separable from the cacophony.

The XO’s undoubtedly a great device for $79. But the FiiO bests it sonically. Moreover, the KA5’s ample features and on-board volume control means that purchasers aren’t merely getting better sound for their additional $50.

With the $129 FiiO Jade KA5 moving on, it’ll face the $149 Muse HiFi M3 in the next round. Keeping with sonic treasures from the 1990s, I selected “Weather with You” from the deluxe edition of Crowded House’s Tchad Blake-engineered and Mitchell Froom-produced Woodface album. “Weather With You” opens with a percussive panoply supporting the song’s signature sitar-esque electric guitar riff. Among other elements, a reverb-laden woodblock sits in the center of the mix, a tambourine is mixed far right, and a deep-mic’d acoustic guitar is panned far left, where it competes with the occasional keyboard flourish. These elements should have their own sonic space and sound timbrally accurate. While I always had a positive impression of the M3, I’m surprised by how handily the KA5 bests it on this track. The M3’s staging is substantially shallower, and it evinces less air than the KA5. In combination, these characteristics create a much more claustrophobic listen — the exact opposite of what I expect from a Blake/Froom recording. Moreover, Nick Seymour’s bass sounds nimble through the KA5 and powerful-but-bloated through the M3. To make matters worse, the aforementioned percussive elements simply sound more artificial through the M3. Wondering if my price-ascending single-elimination review model might miss something in this case, I inserted the Hidizs XO back into the mix. If the KA5 portrays “Weather With You” so decisively better than the M3, how would the XO fare against the M3? In short, the M3 is better than the XO, even if it can’t compete with the KA5 on “Weather With You.”

Given that, I decided to see how the M3 would handle “Falling.” The answer is… much worse than the KA5. Indeed, the M3 really struggled to separate the elements of this dense production. While the M3 never veers into the cringe-inducting muddle of the Hi-mDAC, it fails to provide either the Haim sisters’ vocals or that ascending keyboard their proper sonic space.

Pulling out another MFSL CD favorite, I put on the Elvis Costello-produced “Tempted” from Squeeze’s East Side Story. I decided to focus on John Bentley’s track-defining bassline, the vocal trade-off of the second verse, and Gilson Lavis’s spacious snare and dramatic splash cymbals. Again, though, the KA5 trounces the M3, which simply stages too flat and lacks the KA5’s detail retrieval.

That means the $129 FiiO Jade KA5 moves on to face the $211 Questyle M15. Since I’m comparing the FiiO, Muse, and Questyle in one sitting, I decide to return to “Tempted” to begin this round. I kept the KA5’s settings (high gain, Class H mode, and the linear phase fast-roll-off filter) unchanged and used the M15 in low gain in order to provide more usable volume gradations in Roon, since (as you’ll recall) the M15 does not have hardware volume control. Was the inconvenience of the M15’s lack of settings enough to make the KA5 a slam-dunk winner? Well, actually, no. Pitting against the M15, the FiiO suddenly seemed a bit too polite in its attack and transient impact. The M15 gripped the driver with more authority and rendered each instrument more three-dimensionally than the KA5, which hadn’t previously seemed deficient in that category.

Comparing the KA5 and the M15 reminded me of my power amplifier shootout. The KA5 presents the music in a way that recalls the Benchmark AHB2, while the M15 sounds a bit more like the Bryston 4B Cubed. While I’m loath to ascribe general characteristics to a topology, since there are great implementations and poor implementations of each, the modal sound of THX-style amplifier like the AHB2 is abundant-but-unhyped detail, timbral accuracy, and taught bass, but a bit of a one-dimensional presentation in terms of both overall soundstage and individual instrument depth. Good AB amps like the Bryston tend to keep all of the good parts of THX amps but fix their staging deficiency. Is the sonic difference between the KA5 and M15 as dramatic as the delta between the AHB2 and 4B3? No. But their general sonic tendencies are similar.

Yet this observation might be premature. Thus far, I’ve only evaluated these dongles with the Moondrop Kato and its 3.5 mm cable. Given that, I decided to mix in some different transducers, starting with the most hiss-sensitive IEM I own, the Yanyin Moonlight. This also means switching to the balanced outputs of the KA5 and M15, since I opted for the 4.4 mm cable with my Moonlight.

To test each unit’s hiss without the potential interference of auto-muting mechanisms, I used a silence file from a test-tone suite available on Qobuz. Even on high gain, the KA5 is dead silent with the Moonlight. The M15, for its part, exhibits a very low-level hiss, which does not vary whether the unit is on low or high gain.

Now using the Moonlight IEMs, I cued up the aforementioned “John Henry” from The Philosopher’s Stone. With the more sensitive Moonlight and balanced outputs, the M15’s strengths were more muted, while the KA5’s were enhanced. The M15 seems to retain some of the harmonic profile that I associate with greater soundstage depth, but the KA5 now pulls ahead in raw detail retrieval. David Hayes’s limber bass has better string articulation and Tony Day’s hi-hat and cymbals sound more realistic through the KA5 — not by a wide margin but enough to be noticeable.

What about “Anna Begins”? With this track, the M15’s edge on three-dimensionality returns. However, the KA5’s detail advantage also persists

In other words, while “Tempted” through the Kato seeming to point to a clear win by the M15, both “John Henry” and “Anna Begins” through the Moonlight have moved this battle back into a tossup.

In order to elevate this competition even further, I decided to switch to a much-ballyhooed, much-harder-to-drive kilobuck IEM, the Thieaudio Monarch MK2, which also uses 4.4 mm cable. Putting on “Weather With You,” I found myself in a conundrum. These two dongles both handle the Monarch with aplomb. Subtle differences still exist. The M15 still sounds a bit more three-dimensional, but the KA5’s straightforward presentation may editorialize a bit less.

Perhaps “Falling” will break the logjam. The Monarch MK2 is one of the few IEMs that can handle its dense chorus, provided it has the right amplification. While the difference is subtle, this is a song/IEM combination where the M15’s current mode amplification seems to make a difference. It has just a soupçon more driver control than the KA5, which allows it to keep the overlapping elements of this mix separable.

Given the near-tie between the $129 FiiO Jade KA5 and the $211 Questyle M15, I decided to keep both in the mix while adding the $329 iFi Go Bar. Sticking with the Monarch MK2 and “Falling,” I set the Go Bar to high gain, standard filter, and no IEMatch, then aligned its output level to match that of the KA5 and M15. As I pressed play on the chorus from “Falling,” I wondered if the Go Bar could live up to its premium price or whether we’ve gone past the point of diminishing dongle returns? Switching between the Go Bar, M15, and KA5, a general tonal balance difference emerged. The Go Bar has a slightly darker presentation than the somewhat bright-leaning M15 and fairly neutral KA5. Yet, no details are sacrificed at the altar of warmth when it comes to the Go Bar. Instead, the Go Bar seems to control the Monarch MK2’s drivers in a way that neither the KA5 nor the M15 quite could. The chaotic mix is now wrangled into submission.

Putting “Tempted” on next, the M15 still pulls a bit more depth and detail from the mix than the KA5 does, though the latter certainly doesn’t embarrass itself. The Go Bar, however, is comfortably ahead of both. While it’s warmer tilt sacrifices a bit of air, its superior driver control and low-end heft bring the Go Bar much closer to what I expect from a desktop amp, rather than a dongle.

Knowing that hiss is often the downside of power, I realized it was time to return to the Yanyin Moonlight. Indeed, it’s clear that the Go Bar has the highest noise floor by far when set to high gain and IEMatch off. As with the M15, moving to low gain made no difference in the hiss level. However, engaging the IEMatch on its lower setting (recommended for use with the 3.5 mm output), the Go Bar’s noise floor was reduced to a near-tie with the M15’s. Switching to the higher IEMatch setting (recommended for use with the 4.4 mm output), I encountered dead silence.

Sticking with the Moonlight and the Go Bar on 4.4 IEMatch, I matched my levels again and decided to introduce a new audition track. In tribute to my Ohio roots, I put on “Funk #49” by the James Gang. Produced and co-engineered by the legendary Bill Szymczyk, this suburb cut sounds wonderful on the MFSL SACD of James Gang Rides Again. Comparing the KA5 and M15, the latter’s somewhat brighter tilt provides both Joe Walsh’s guitar and Jim Fox’s cymbals with a bit more metallic bite. However, as was the case earlier when using the Moonlight, the KA5 seems to edge out the M15 when it came to detail on Fox’s hi-hat. Indeed, the KA5 may equal — or even exceed — the Go Bar in that specific area. But in just about every other area, particularly low end authority, the Go Bar is in a class apart from both the KA5 and M15.

Even though my dongle duty is limited to IEMs, I realize that other audiophiles may be interested in using full-sized headphones. So I decided to put the KA5, M15, and Go Bar through the paces with the Drop version of the notoriously hard-to-drive Sennheiser HD650, the HD6XX. For this audition, I finally put the M15 into high gain, disabled the Go Bar’s IEMatch feature, and matched levels again. Putting on “Anna Begins,” I was impressed by the Go Bar’s control over the HD6XX’s driver. With its volume set to 94, the KA5 retains its composure but doesn’t seem to be able to drive the HD6XX with power necessary to give its low end a sense of control and authority. Turning to the M15, with Roon set to a scant 26, the HD6XX now conveys more weight when reproducing the kick and bass guitar. Moving to the Go Bar, things improve further, though only modestly. All told, I wouldn’t recommend the KA5 for hard-to-drive headphones. The M15 and Go Bar are perfectly cromulent for this task, though no one will mistake them for a desktop amplifier.

Thoughts on the Top Four

Of the six dongles under review, the $79 Hidizs XO, $129 FiiO Jade KA5, $211 Questyle M15, and $329 iFi Go Bar each have a case to be made for their consideration.

The XO is affordable, well-made, and functionally straightforward. It’s tonally well-balanced, but its round presentation robs transients of some needed attack, and it’s far from the last word in resolution or power. It’s a good choice for the budget-conscious, but those who can spring for one of the other three dongles should. While pricier, each offers more in the way of features and sound.

The KA5 is, in my estimation, the price-to-performance champ of these six dongles. Yes, at times it does lack a bit of three-dimensionality. It’s also not recommended for power-hungry over-ear headphones like the HD6XX and can even lack a bit of heft even with low-sensitivity IEMs like the Monarch MK2. But with most IEMs, it’s at most slightly behind the M15 and Go Bar when it comes to tonality, and it may even be the best sounding dongle with sensitive IEMs such as the Moonlight. Add in its abundant user-selectable settings and consistently stable operation, and it’s hard to imagine a better dongle for the price.

For an extra $80, you might prefer the M15. Its main advantage is better driver control and a bit more depth than the KA5. If you’re someone who plans to use your dongle with full-size headphones or prefers the tonality of class AB amplifiers to that of THX-style ones, then you’ll probably think the extra money is worth it for the M15, even with its limited features. But if you don’t plan on using your dongle with hard-to-drive transducers or you prefer the just-the-facts style of multi-zero amps, then you’re probably better off sticking with the KA5 given its lower price and better features.

Sitting at the top of the heap is the $329 iFi Go Bar. It commands a premium price, but it backs it up with performance, both in terms of quality and power. Even when a pairing seemed synergistic between a dongle and an IEM — such as the KA5 and the Moonlight — the Go Bar could at least match it. In most other cases, it was clearly the best amp for the transducer, whether it be the Monarch MK2 or the HD6XX.

Conclusion

Ultimately, I think the KA5 is the best choice for the budget-conscious audiophile who stays away from power-hungry IEMs and headphones. To this reviewer, the KA5 is easily worth the extra $50 over the XO, which relegates the latter only to those who really want to stay in the $75-dollar range for their dongle. Meanwhile, the Go Bar is best choice for the audiophile willing to spring for the absolute best dongle and the audiophile who plans to use power-hungry IEMs and headphones. The M15 ends up a bit in-between as the best choice for the audiophile who wants a dongle with minimal source power consumption and the audiophile who wants to use harder-to-drive IEMs and headphones but doesn’t have the budget for the better-across-the-board Go Bar.