REVIEW: Hidizs AP80 PRO-X Music Player - touchscreen, unbalanced and balanced headphone output, dual ESS ES9219C DAC. (And time for PAF 2023.)

Digital Audio Players (DAP) are not a class of components I've explored as thoroughly over here at the Musings. However, over the last few years, as smart phones have ditched their analogue headphone outputs opting for Bluetooth audio or (often cumbersome) DAC/headphone amp dongles, what's an audiophile to do when we want to listen to high-quality playback on the go? Perhaps a small DAP can satisfy this need.

Recently, the folks at Hidizs sent me one of their most recent Hidizs AP80 PRO-X (currently around US$200) for an honest review including objective testing of course. This is the 3rd evolution of the Hidizs DAP product line which started with the AP80 in 2018, followed by the AP80 Pro in 2020, and this newest AP80 PRO-X in 2022. As you can see with that picture of the device in my hand, it's a cute, flat, squarish music player measuring only 6.1x5.6x1.4cm, and weighs a mere 70g.

The aluminum and glass body, bright Samsung 480x360 2.45" touchscreen with good viewing angle, contrast and saturated colors, feels sturdy in the hand with convenient volume control knob, and 3 smaller physical buttons on the side.

I. Contents, Design and Features

Here's a look at the open box with contents:

Notice the included short USB-C-to-C OTG directional cable and longer USB-C-to-A. Manual and various literature (10% discount card, serial number card, QC card), as well as  the nice touch of the extra plastic screen protectors. A case is not included unfortunately and the official leather case can be purchased for around US$25. As you can see in some of the pictures, I bought the blue-colored one.

Here's a better look at the red-accented ALPS push-button knob for power/volume control along with 3 buttons to pause/play, skip forward and back on either side:

In use, the small buttons are unobtrusive, not easily pressed accidentally and the indented tactic feel of the volume knob allows convenient volume change. The device looks nicely modern with angled edges that are not uncomfortable and the edges add a bit of stability when held so as not to slip out of the hand.

At the bottom of the device, we can see the single-ended 3.5mm headphone jack as well as 2.5mm balanced analogue output flanking the USB-C connector for data transfer.

Notice the small microSD card slot on the left. This device does not come with any storage so you'll have to stick up to a 512GB card in there (I'm using an inexpensive Samsung EVO Select 512GB ~US$40). USB file transfer speed is reasonably good averaging around 20MB/s to and from the SD card; this is clearly faster than something like the PonoPlayer transferring at an annoyingly slow 4MB/s! The DAP reads standard FAT32 format so if you want faster transfer speed, take out the card and use an external 5Gbps USB3 card reader to your computer which should be able to hit 60MB/s but dependent on memory card speed.

Here's the "About" screen with the 512GB card inserted. 461GB total available. Assuming a CD is about 300MB FLAC compressed, that's enough for at least 1500 lossless compressed 16/44.1 albums in this tiny package. I'm running the latest firmware 1.0:

The AP80 PRO-X operating system is based on HiBy OS 3.0 running off an Ingenic X1000 MIPS processor. There's also an FPGA they call the "HBC3000" for other processing like DSD64/128/256 playback and realtime conversion to PCM (8x). Native PCM sample rate up to 32/384kHz supported. When first turned on, it takes about 10 seconds to boot. The UI is responsive and touchscreen accurate considering the small screen.

At the highest interface level, there are some "apps" like the Settings app, Bluetooth control, step counter, and even a text reader which is a neat idea if one must read with such a small screen!

The vast majority of the time, one will be in the Player "app" for music playback of course:

Notice the "Update database" item which you can click each time you copy new music over to get the album recognized by the player immediately. There's also an auto update option in settings.

The internal DAC has been upgraded in this latest model to dual ESS Sabre ES9219C chips released in 2019, which is a low-power DAC+headphone amp using a "HyperStream III" architecture.

No need to go into too many details about the OS I think, it's easy to pick up and navigate. There are plenty of ways to adjust the sound quality including a selection of ESS digital filters, a 10-band EQ, and a DSP feature called "MSEB" (Mage Sound 8-Ball Tuning - looks like it's a parametric EQ-based adjustment converting frequency bands to subjective characteristics of sound; see this YouTube video with some details on the frequency affected for each item on the Android app).

I'll discuss further in the measurements section, but just quickly, I don't think the digital filter options made any difference even though I can click on them to select. Given all the features and variations in settings (like crossfade, ReplayGain, "Soundfield" width expansion effect, gapless playback), it's possible that I didn't get the settings right; not that digital filters change the sound quality much.

Compared to previous AP80 and AP80 PRO models, this newest PRO-X model does not have FM radio. If this is important to you, the older PRO model is still available.

The USB-C port is used not just for storage, but this device can also be used as a USB DAC which makes it convenient for running measurements.

Hidizs AP80 PRO-X connected to laptop as external USB DAC - notice that it's currently playing "48.00kHz/24bits" as per the small text. IEMs are the KZ PR1 with planar magnetic drivers.

The supplied USB-C-to-C cable worked well with my older Samsung Android 11 tablet and Huawei Android 12 phone. The short cable is directional, make sure to plug the side with Hidizs logo into the digital source and the other end into the player/DAC.

One other convenient feature is that you can swipe up from the lower edge of the screen to access a quick "shortcut" menu:

The shortcut menu is convenient for easy access to turning on/off Bluetooth, select low or high-gain output levels, turn on/off USB DAC mode, and turn on/off the line-out mode which fixes the volume at 1Vrms on the single-ended output and presumably 2V balanced (not tested). Be careful not to accidentally turn this on with sensitive headphones plugged in while playing something. Also there's quick access to the forward/play-pause/backward buttons, screen brightness and volume level.

To round out the feature set, there's also Bluetooth 4.2 capability with wide codec support including apt-X, LDAC, AAC, and SBC. It also supports the HiBy UAT "Ultra Audio Transmission" with up to 1.2Mbps transmission speed (highest for LDAC is 990kbps) and sampling rate up to 192kHz. Of course like other Bluetooth transmissions, this would be a lossy signal. In order to use this feature, the wireless headphone will need to be compatible with UAT like the HiBy WH2. Here's a look at the Bluetooth menu:

II. Measurements

As usual, after I spent a few days listening to the device, I placed it on my test bench to have a look at objective performance. For this DAP, I used the E1DA Cosmos ADC, and Scaler; the APU was not needed. At this time, I don't have 2.5mm balanced cables for testing so I'll just stick with the much more commonly used 3.5mm single-ended output for these measurement. (Let me know if you really "need" to know how this device performs with the balanced output!)

Let's start with the oscilloscope tracing of a 1kHz 0dBFS sine wave, 100% volume into low and high gain output levels, no dummy load.

The difference between "Lo" and "Hi" gain is +6dB or double the output RMS voltage. We see a clean 1Vrms level at "Lo" and 2Vrms at "Hi" gain. I am impressed by the precise R-L channel balance! Basically perfect. A quick test using 300Hz and 4kHz signals, one in each channel at 1V into a challenging 20Ω load shows better than -70dB crosstalk. Crosstalk measurements are also affected by cables used and already this is more than adequate for great stereo separation.

Although there are a number of digital filter options as shown in one of the pictures above, for some reason the output is basically "stuck" at the "Linear Phase Sharp" setting even when I select one of the other options. I do see some small variation with the "Corrected Minimum phase" but other than that one, the rest seem the same. To be honest, this is fine with me since the linear phase sharp filter is my preferred most-accurate filter setting anyways.

Here's the impulse response and Digital Filter Composite graph:

Impulse response maintained absolute polarity. There's a fair amount of intermodulation which suggests that the measurements are not going to be showing ultra-high fidelity results like some of the highest resolution desktop DACs. Great to see the absence of overload behavior with the white noise 0dBFS signal (yellow).

Yes, this device supports MQA decoding up to 8x base sample rate (48 x 8 = 384kHz). However, interestingly, I noticed that this unit did not recognize decoded 24/96 files intended for MQA "rendering" as with some lower-end DACs like the Dragonfly Black. Given the current state of MQA, I don't think there's any further reason to support it and presumably in time, once the current batch of devices that have MQA designed into them has been released, subsequent generations will likely see the MQA feature deprecated.

Notice the "MQA Studio" flag (equivalent to the blue LED) instead of indicating "24/44.1 FLAC" which is the actual file bitrate and format.

Since the ES9219 DAC is supposed to be able to "render" MQA as a built-in feature, I wondered if the FPGA is always actively upsampling and monitoring for an MQA signal to decode+render (rendering is basically MQA upsampling). This might explain why changing the digital filter setting made no difference and the automatic "rendering" with the ESS DAC chip doesn't work when presented with decoded MQA 24/96 data.

Moving along, let's have a look at the single-ended 3.5mm output impedance: 

Excellent low output impedance! This music player/DAC will have no problem handling even very low impedance headphones.

We can verify the low output impedance with some frequency response sweeps including the use of the Polk Ultrafit 2000 actual headphone load - see impedance curve here:

As you can see, I had to separate the frequency response curves otherwise they would basically overlap on each other. With the very low output impedance, this little DAP has no difficulty with maintaining "control" of even the most variable low-impedance headphones.

A closer look at the frequency response and phase with higher length sweep (1V into 75Ω load):

There are no issues at all with sub-bass playback down below 10Hz. A mere 0.4dB dip at 20kHz. No concern at all with any phase shift across the audible spectrum.

Moving along, let's think about how much power this little device can provide to the headphones. As per my standard testing, I'll use 20/75/560Ω loads to represent low, medium, and high impedance headphones; all results are with both channels driven. I set the player to "Hi" gain to maximize potential output level.

As usual, I set my threshold for power measurements at the "high fidelity" level of 0.1% THD(+N). At high impedance like 560Ω, it doesn't take much power to achieve around 2Vrms peak level. With a medium impedance 75Ω load, the little music player is capable of 43mW and we see the current limiting with a 20Ω load providing 98mW maximum. This result is consistent with Hidizs's specs indicating "70mW @32ohm" into the single-ended output.

Suppose we want to use this just as a DAC, let's see what the THD+N looks like directly connected to the E1DA Scaler (100kΩ impedance):

At the Hi-Gain setting, we can see the best THD+N is around -95.5dB (0.0017%) at 300mV. As with the other graphs above, at higher output levels, the 3rd harmonic predominates followed by 2nd and then the higher order ones.

Here's the linearity graph into 75Ω load with mild clipping into 0dBFS, Hi-Gain:

Excellent. Less than 0.5dB variation down to -120dBFS.

And one more stepped sine at 1V into 75Ω looking at THD(+N) vs. Frequency to make sure that distortion remains relatively steady across the audible spectrum:

THD+N is a combination of harmonic distortions plus noise. The higher gain setting subtly increases the noise level. In use, if you're pairing this player with sensitive headphones and playing music at Lo-Gain, maybe around 80% volume (0.3Vrms peak), here's the THD+N of a 1kHz tone:

 

That FFT above is about the best THD+N achievable with this player, around -98dB/0.0013%.

As a general measure of resolution, here's my "standard" 0.5Vrms Total Distortion + Noise measure using a Triple-Tone signal (24/96):

A result of -87dB TD+N (0.5V into 20Ω) is good especially for a low-power portable device like this. You can see the various intermodulation and harmonic peaks in the FFT. There's 88dB distortion-free range below the primary signals. For context, some of the best headphone outputs like the Sabaj A20d 2022 desktop DAC achieve around -100dB TD+N.

A reminder that I'm measuring only the single-ended output here. It's quite possible that the balanced output would measure better than -87dB.

Finally, let's have a look at jitter:

This looks really good. We can easily see the low-level jitter modulation tone in the 16-bit signal. And a couple of very low-level sideband pairs in the 24-bit signal basically down around -140dB from the primary signal!

In modern high-performance devices regardless of price, jitter is almost always not something an audiophile should be concerned about.

Although not measured, the 2.5mm balanced output sounds great with Drop+HiFiMan HE-4XX planar headphones (Ranko Acoustics cable shown here). Excellent clarity and plenty loud!

III. Subjective

I used this little player over the last 3 weeks daily to get a sense of how well it works. Overall, I found it unobtrusive in the pocket when working out. The user interface is responsive, easy to learn without needing to consult the user manual. With the larger round volume knob as landmark, it's easy to figure out the smaller 3 buttons while in the pocket.

Even though it's a small 800mAh lithium battery inside; clearly this is a very power-efficient player. While there's no fast-charge features (~1.5 hours from zero to full charge using typical 5V/2A USB power supply), the advertised 8-11 hour single-ended battery life seems about right when paired with high-sensitivity IEMs. Obviously this would vary further depending on screen usage, volume and drops to an advertised 6-8 hours with balanced out.

While most users I'm sure would be focused on analogue outputs, I used Bluetooth over the weeks connected to my 1More SonoFlow (LDAC) and AirPods Pro Gen 1 (AAC) wireless earphones. I had no issues with making the connection and range was about as good as my cell phone (easily able to walk around my house between the 3 floors without issue).

As for sound quality, well, let's talk about a few albums and what I heard.

Noel Gallagher's High Flying Birds' Council Skies (2023, DR6) is the latest from the ex-Oasis brother. Mostly midtempo rock/pop written during the pandemic. It's good though if you like the genre. To be honest, this is not a great sounding recording as you would imagine with that DR6 result. However, I think most music lovers appreciate that the "emotional connection" we have with music is not just because of sound quality. We might connect with the artist's personality, their life journeys, catchy rhythms and melodies, perhaps connect deeply with the meaning in the lyrics. It's these latter elements that I find enjoyable about this album.

At 57, Gallagher remains controversial for what he says and how he says it, typical fodder for tabloids. Regardless of what I think about his feud with his brother or some of the silly political stuff he says, I can certainly respect the artistry in Gallagher's music even if the album sounds suboptimal qualitatively.

Whether it's the structure or heartbreak nostalgia of "Easy Now" reminiscent of Oasis, the joyful cynicism of "Love Is A Rich Man", or the attempt to rekindle the wonder of youth in "Open the Door, See What You Find", this album speaks to me as someone in the 6th decade of life. Compared to the silliness of the lyrics in Paul McCartney's Egypt Station that I talked about a few years back, there is maturity in the lyrics and music here. Nice pacing and energy on tracks like "Council Skies" and "There She Blows!". Plus the dance version of "Think of a Number (Pet Shop Boys Magic Eye 12" Remix)" is catchy on the Deluxe Edition.

Let's jump across genres and generations now. The Spider-Man: Across the Spider-Verse soundtrack (2023, CBR320 MP3) is a "clean" rap/R&B collection of collaborations from Metro Boomin (aka Leland Tyler Wayne) with many others. Unfortunately I still haven't had time to check out the movie but my teenager son tells me he was blown away so I'll take his word for now. 

Anyhow, this is an enjoyable collection if you're into modern pop. Lots of deep bass beats, synth effects, copious collaboration I guess also reflective of the frenetic pace of the movie itself (or so I've been told). Have a listen to the first track "Annihilate" to get a taste. My favorites are the slower tempo "Link Up" and "Am I Dreaming".

If you like the music, make sure to also have a listen to the soundtrack from Spider-Man: Into the Spider-Verse which was a big hit back in 2018. Regardless, the AP80 PRO-X did an excellent job with the multilayered multitrack complexity of music like this.

I didn't know David Chesky's daughter, Paloma Dineli Chesky, is a vocalist. She released this album Soul on Soul (2022, DR11) recently. A well-recorded female vocal jazz album in the tradition of others from the Chesky label. It's hard to imagine from the beginning phrase on "Something's Got A Hold On Me" that this is a 14 year old singing! Interesting renditions of "Nobody's Fault But Mine" (here's Led Zeppelin) and "It's A Man's World".

The album sounded great through the Hidizs AP80 PRO-X. It's an example of a clean, high-fidelity "audiophile" recording with nice dynamic range, excellent details which nicely highlight her natural ability for vocal control. Great stuff; I'll be keeping an eye on Ms. Chesky's career ahead.

Let's go further into higher quality, excellent sounding albums; this one a classical hybrid SACD by Tine Thing Helseth & The Norwegian Chamber Orchestra of Trumpet Concertos (2007, DR13). Staying with the idea of a youthful performer, Helseth would have been 20 when this album was released. The trumpet solos throughout the album epitomizes a "silky smooth" sound with excellent accompaniment. Loved the Haydn Trumpet Concerto in E flat major. Here's a video of the 3rd movement from 15 years ago.

I had a listen to this album through the Hidizs player with a DSD64-to-16/48 PCM conversion, Drop+HiFiMan HE-4XX headphone to balanced 2.5mm output as shown in the picture above. The player had no difficulty driving these ~43Ω headphones (measured here) to more-than-adequate volume levels without using the Hi-Gain setting over the balanced cable. While I find the HE-4XX a bit recessed in the upper-mids especially noticeable with some vocal recordings, it works well with an album like this showing off the "airiness" of tracks like the Albinoni "Concerto à cinque in B flat Op.7" Adagio (track 5).

This SACD also has a 5.1 multichannel mix for those with surround systems.

As always, listen for yourself. Here's my standard AMPT recording from the single-ended analogue output of the Hidizs AP80 PRO-X directly to the RME ADI-2 Pro FS DAC, captured at 24/96. Let me know if you hear any concerns around dynamics, channel separation, clarity, frequency response, speed or tonality/timbre compared to other AMPT device recordings.

Hidizs AP80 PRO-X Music Player AMPT

(dual ESS ES9219C DAC, music played back from microSD)

NOTE: Amazon Drive is discontinuing their service by December of this year. I've started hosting file downloads elsewhere. But if there are downloads from previous blog posts you want to keep, make sure to download them over the next few months!

Size comparison of the AP80 PRO-X with the AKG Q701 headphone. If you look closely, you'll see that the music being played is a native DSD64 file (in .dsf, no support for WavePack DSD compression unfortunately). This little digital player can handle up to DSD256 with options to convert to PCM, DoP, or native playback and DSD gain compensation is available as needed in the settings.

IV. Summary

The Hidizs AP80 PRO-X (Canada link) is small, has a fast user interface, and accepts all kinds of PCM files up to hires 24/384 (take your pick of FLAC, APE, WAV, ALAC, AIFF lossless as well as lossy MP3, WMA, AAC, OGG), plus DSD up to DSD256 (DFF and DSF). Yeah, it does MQA decoding as well.

Features cover the bases from a simple 10-band EQ to various sound-shaping options through their MSEB DSP. I quite like the "soundfield" setting, the ability to smoothly transition with crossfade, and the ability to use ReplayGain to keep output levels stable between tracks is an essential feature IMO. The metal enclosure, volume knob, and firm buttons feel good in the hand and exude quality. The 2" touch screen has excellent resolution, viewing angle and color. It is small though, so for those with fat fingers, you might make a mistake here and there tapping on an on-screen button. Such is the compromise to keep the package small, light and easily pocketable. You'll notice a touch of warmth after hours of music playback through the balanced output, nothing uncomfortable.

Loading music onto the machine is easy by basically plugging the USB-C into your computer then cut-and-paste music files. No need for any silly app like iTunes just to get your music into the box. These days a 512GB microSD card is cheap and will easily hold >1000 lossless compressed CD-quality albums. Data transfer speed of 20MB/s won't break any speed records, but it's very reasonable in daily use - basically a CD worth of lossless-compressed music transferred in 15 seconds.

This player sounds subjectively excellent when paired with good headphones of course. Technically, utilizing dual low-power ESS ES9219C DAC/headphone amp chips has resulted in a device with very low output impedance (<0.1Ω) and will pair well with basically anything that's reasonably sensitive. Output level linearity is simply excellent and the channel balance is perfect on the one tested. Frequency response with all EQ/DSP off is flat and this will deliver sound from the lowest sub-bass to the highest audible treble without issue. For the small size, battery life is reasonable and should last pretty much a full day's usage depending on how loud you listen and with what headphones. One could never have enough battery power however so a few more extra hours would always be appreciated.

At the higher gain mode, the single-ended output will hit 2Vrms and will provide up to 100mW into 20Ω. Using the 2.5mm balanced output could provide up to a further +6dB boost depending on other limiting factors (like current demand); at the expense of shorter battery life which the company advertises as "6-8 hours" from "8-11 hours" with single-ended out.

As a DAC, distortion tests show good THD+N of around -95dB with primarily 3rd and 2nd harmonics predominating. A 0.5Vrms into 20Ω Triple-Tone TD+N result of -87dB is very good compared to other portable devices I've measured including something like the more expensive iFi GO Bar which achieved -78dB. Jitter is not an issue - at all.

It worked well as a small Bluetooth transmitter with good range for wireless headphones covering LDAC, apt-X, and AAC codecs beyond SBC. It also supports HiBy's UAT codec if you have such headphones. I would recommend turning off the Bluetooth transmitter to save power if not needed.

I hope it's clear from the discussions above that at the current asking price, I think the Hidizs AP80 PRO-X is a great deal for a DAP if you're in the market for such a device with a strong feature set and objective performance.

As per the images above, I have the leather Hidisz case (<$25). It's a simple slip-on case that leaves the volume knob/buttons side open, touchscreen easily accessible and of course the USB and headphone ports open. You'll only need to take it out if changing microSD card. I have no concerns with the quality of the small case other than the fact that it does make the volume knob less easily accessible; still usable with a little practice. Not an essential accessory.

Related, for consideration, you can also plug the AP80 Pro-X into the Hidizs HD80/HD80s (HD80 is a dock-like unit, while the HD80s connects with short USB-C cable). This will basically transmit your digital data to the HD80(s) for playback with its higher resolution ESS ES9281C PRO chip, provides higher power out, and employs a 4.4mm Pentaconn balanced connector.

One last thing, let's do a quick comparison... While I don't typically review many DAPs on this blog, I've had a few here at home over the years like these:

Various music players, release dates, and size comparison. Notice the more contrasty and brighter Samsung screen of the AP80 PRO-X photographed at 30% brightness. PonoPlayer at 50% brightness setting, iPod 100%.

Many audio lovers will be familiar with the iPod of course. I measured this 5th Gen back in 2016. Unfortunately it has output impedance >10Ω which is very high these days. Also, it's limited to 48kHz samplerate and isn't really capable of >16-bit dynamic range.

The 2015-released PonoPlayer (reviewed here) is however capable of hi-res playback. For comparison, let's have a look at the Triple-Tone TD+N signal; note that this isn't actually an apples-to-apples comparison because the Pono's single-ended output isn't quite capable of 0.5V into 20Ω with my test signal, just up to 0.4Vrms:

For brevity, let's just overlay the right and left channel FFTs.

The PonoPlayer is straining pretty hard into the 20Ω load achieving -44dB TD+N and also about 44dB distortion-free range below the primary tones. While much better than the iPod, the PonoPlayer's output impedance is still quite high at ~3Ω. MSRP for the PonoPlayer was US$399 back in the day.

Great to see the evolution of the DAP market and the resolution available these days!

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Time for Pacific Audio Fest 2023; second showing.

I'll take my time this year to hang out with a few fellow audiophiles, enjoy some music, and take some photos. No need for rushed coverage this year I think, compared to the rapid-fire last time. :-)

A couple of shots...

Campfire Audio - Trifecta "Astral Plane". It's very pretty.

New Børresen M6 speakers (US $550k) premiere at PAF2023 + Aavik room. Clean, clear, hi-fi sound. Impressively good bass impact.