Why I use a dongle despite having a headphone jack.

Having come from the Essential PH-1 I was delighted to see that the Pixel 4a came with a headphone jack. I rarely missed the headphone jack during my time using the PH-1. The Essential phone came with a dongle, which I used maybe twice, DJ'ing in a friends passenger seat.

I had already purchased MPow Cheetah 3's for use at the gym. They supported AptX and sounded better than the SkullCandy FMJ's that were collecting dust since high school.

When my Pixel arrived, I dusted off my SkullCandy FMJ's and kept then on my night stand for use before sleep.

Finding solace in PlexAmp after GPM's shutdown

I really enjoyed Youtube Music from a streaming perspective. However I started to feel like 'owned' content is not a priority with the new client. So around the time Google Play Music shutdown for good, I began hosting my music library under a Plex Server.

In as little as ten minutes, I was setup and streaming my Hi-Res flac files remotely to my phone using PlexAmp. The same MPow cheetahs still sounded very well however I noticed one evening, during 'The Devil and God are Raging Inside Me' there was much more details with the FMJ's than I was used to hearing.

I spent a week listening to the Pixel 4a from it's built in jack and the Essential 3.5mm dongle unable to hear a huge difference with either of my headphones. 'I'll try both in the car' I thought.

I jumped in my 4runner, switched from Bluetooth (SBC) to aux, and began playing 'Where I Wanna Be' by Big Gigantic. Immediately I noticed that I had to turn the volume up well past 18 (Bluetooth) all the way to 32. Not only that, there was almost no bass compared to bluetooth!

This makes no sense, most audio quality comes from your audio system, not from fancy codecs, and Bluetooth over SBC should surely sound worse than aux!

Not all Headphone Jacks are created equal

Since nothing added up, I went down a rabbit hole reading about different DACs, speaker systems, and specifically why LG phones notoriously 'sound better' than other phones with headphone jacks.
Fortunately, the Pixel 4a was given a full evaluation of it's audio capabilities. Here you will find a chart that is likely meaningless to you.

What matters in this graph? If you look on the right side, there is what looks like a logarithmic plot. This is the sound output at each frequency the phone can respond to. Ideally this would be a smooth line, however distortion can happen for several reasons (wire, EMF in the phone and air, etc).
A better performing device will have smaller variances in the output and have fewer and shorter spikes on this graph. The Pixel does very well in this regard.
What is bad on this chart is there is only an output of 0.31 Vrms. This explains the low audio output, and the lack of 'punch' or substance in the bass when I used aux in the truck.

If you read that thread, the Apple USBc - 3.5mm dongle is suggested because it can push more voltage and costs only 9$ and phones notoriously have poor audio characteristics (to drive down manufacturing costs).

Understanding the USB Audio ecosystem

Sum up a ton of research into a few paragraphs? Challenge accepted.
Phones with USBc have two options for outputting audio through the usb port:

• USBc Analog Audio alt-mode (AAM): In this implementation, the USBc port is downstream from a DAC which converts a Digital audio stream into voltage which sent from the data pins to a headphone jack. This effectively will sound exactly like a headphone jack.
• USBc Audio Class 1/2: In this implementation the device does not need a DAC. Audio data is sent digitally from the usb port like a computer would, this digital data will be converted to analog using an external DAC (our dongle). The DAC is supplied power from the host device via USB Power-Delivery. This will sound as good as the DAC and power source can supply.

If you've bought a headphone dongle and found it didn't work with your device you probably have a device that uses the latter method. Afaik only some HTC phones actually used AAM. Now you know what to look for!

How I fixed the issue

Instead of just buying the Apple dongle, I spent another few nights doing research into USB DAC's. My notions is that, ideally I could buy a dongle with a high quality DAC I can bring the audio quality with me to every new phone I get.

I was only fine with spending more money on a dongle if it actually sounded better, and if it was USBc (futureproof and small). I came up with three devices:

• Sonata HD
• Meizu HiFi-Pro
• NextDrive Spectra X (usbc)

The Sonata HD did not perform much better than the Apple dongle which was half the price so I wasn't very interested in it.
The NextDrive Spectra X however was very interesting. It has the same DAC implementation as the LG Quad Dacs. However it's very expensive and the barrel that contains the drivers is very large.

Eventually, I came across the Meizu HiFi Pro (there is a Pro and Standard version). The Pro specifically has a CS43131 DAC which can decode up to 32-bit/384kHz, and an OPA 1622 acting as an amplifier. This means it would draw slightly more power from my phone in order to achieve a higher volume output. It looks really good, it's small, discrete and aluminum. What else could you want?

This Dongle > headphone jack!?

Fortunately, all three of these dongles were tested on AudioScience Review. The Spectra X obviously outperforms the other two dongles, but the Meizu HiFi Pro comes surprisingly close for a little less than half the price.

Comparing this to the Pixel 4a, we see slightly more distortion, however the distortion is very small and at inaudible levels!
Additionally, the noise floor is lower (140db) than the 4a (120db) which means no audible hissing when there is silence during playback.
If you read on further, this dongle is pushing out volume comparable to desktop DACs which is great to see.
Additionally, the output is sitting at 1.7 Vrms!

On top of this, the Meizu HiFi Pro can decode up to 32/384khz so it more than passes the Sony HD audio specification and beats out the Pixel's 16/48khz decoding capability. So I think we've found our match.

The Meizu HiFi Pro is extremely hard to find, but I did eventually find and import it through AliExpress for ~60$ with shipping. Worth it? I think so.

Ok, but how does it sound

I had about two weeks to wait while the dongle made it's way through so I started shopping around for new earbuds. I came up with two choices but settled on DoCooler VK4 because how can you go wrong for 20$?!
They have two drivers (High and Low) in each ear, and I geek out over the Carbon Nanotube Diaphragms. And they're not ugly!

Some how I lucked out and both the dongle, and the headphones arrived within the same hour. I popped the headphones and dongle into my Pixel and started my 'test' playlist I had built while I was waiting:

• Where I Wanna Be - Big Gigantic 24/44.1khz
• Movement - Hozier 16/48khz
• Pools - Paramore 24/48kh
• Cigarettes - Tash Sultana 24/48khz
• Jesus - Brand New 16/48khz
• Brain in a Fishtank - Shpongle 16/48khz
• Open Your Mind - Bassnectar 320kbps
• Perfect - Dance Gavin Dance 16/48khz
• Summertime Gladness (Tree City Sessions 2) - Dance Gavin Dance 16/44khz
• Bat Country - Emancipator 16/44khz

I immediately noticed a difference between the VK4's, VK4+Meizu Dongle, and my old SkullCandy's. I've head Audiophiles talk about 'sound scapes' and I chalked it up as word candy however it really is a thing. You can close your eyes with these headphones on and feel where each instrument is spatially. I thought I would only get that with a speaker system!
Running the headphones through the Meizu Dongle I had heard cymbals in 'Where I Wanna Be' I had never heard in the song before! On 'Perfect' I thought 'what is this clicking? .... IT'S THE GUITAR PICK'. In 'Cigarettes' I can hear the air reverberate in Tash's kick-pad. Money well spent? Lets see.

After enjoying this playlist on the VK4's I moved to the 4runner, and plugged my phone and Meizu dongle into my stereo. I put on 'Open Your Mind' and was hoping to hear the subwoofer go off. When I reached the drop at 1:01 I was convinced.

My car stereo did not sound this good with any other device I had plugged into it! Especially the bare Pixel 4a.

Conclusion

Ignoring my anecdotal experience, we still have the actual test results of the Meizu HiFi Pro and the Pixel 4a's 'anemic sound output'. The Meizu dongle without a doubt sounds much better than my phones built in headphone jack.

When I had my Essential Phone, I wondered "Why do people miss the headphone jack? Bluetooth is everywhere, AptX streams at CD quality". I repeatedly got 'the headphone jack just sounds better' and I called them crazy.
With the advent of super High Resolution Audio (24-32bit DSD) I acknowledge bluetooth once again falls behind unless everything you own is CD Quality or less.

However, now that I have tried the Meizu HiFi pro I still wonder. Why do people miss the headphone jack? The dongles sound the same, if not better.