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Apple AirPort Express Audio Performance
Model A1392 / MC414LL/A (2014)
© KenRockwell.com. All rights reserved.

I've bought about 12 of these at Amazon; Adorama and B&H are also great places.

Intro   Specs   Measurements   Recommendations

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apple airport express

Apple AirPort Express (8.3 oz./235 g, about $99).

This free website's biggest source of support is when you use those or these links, especially these links to them at Amazon, at Adorama or at B&H, when you get anything, regardless of the country in which you live. Thanks! Ken.

apple airport express

Apple AirPort Express.

 

June 2015  All Reviews  >  Audio Reviews > Apple reviews

How to Make a Large Wireless Network

How to Make a Multi-Room Audio/Video System

See also the audioengine B1 Bluetooth Audio Receiver and old AirPort Express.

 

Good: Fantastic audio quality, full 2 V RMS output, beautiful, sturdy build and small.

Bad: Much clumsier to set up the first time than Bluetooth.

 

Introduction         top

Intro   Specs   Measurements   Recommendations

Adorama pays top dollar for your used gear.

B&H Photo - Video - Pro Audio

This Apple AirPort Express can be used as a high-perfomance DAC to play-out from a Mac or iOS device either over WiFi, or over wired Ethernet.

It's easy to configure a slew of them to sit in different rooms of your home, and play to them from your devices.

Simply plug the AirPort express into your HiFi, stereo, power-amplifier, home music system or powered speakers, and it will play from your iOS device or your Mac.

Use a 3.5mm cord to connect to many powered speakers.

Use a 3.5mm to RCA cord to connect to any stereo system or power amp or preamp, or many other powered speakers.

Since you can control the volume from your device or Mac, you can skip the preamp for even better fidelity; just plug it directly into your power amplifier.

Use a Mini TOSLINK cable to connect directly to the optical SPDIF digital inputs of a DAC or stereo receiver. The AirPort Express has its own great DAC, but if you prefer to use another, no problem.

The TOSLINK output is the same connector as the 3.5mm analog connector. You can use only one at a time. Use a Mini TOSLINK cable to plug into other TOSLINK SPDIF inputs.

 

Specifications         top

Intro   Specs   Measurements   Recommendations

 

Model Number

A1392.

 

Marketing Product Number

MC414LL/A.

 

Inputs

Wi-Fi and Ethernet.

 

Outputs

Stereo 3.5mm analog at 2 V RMS, Mini-TOSLINK optical digital SPDIF (same jack).

 

Power

110-240 VAC 50-60 Hz.

Actual consumption at 120 VAC: 2.3 watts.

 

Included

Cool Apple power cord.

The power cord is so nice that some rich folks in Leichtenstein buy these just for the cords for other equipment, and throw away the AirPort Express!

 

Mechanical

Plastic case.

 

Size

About 4" (12 cm) square.

 

Weight

8.275 oz. (234.6 g), actual measured.

 

Quality

Made in China.

 

Price

$100 or less.

 

Measurements         top

Intro   Specs   Measurements   Recommendations

Output Levels   Output Impedance   Noise & DC Offset

Channel Balance   Frequency Response   THD

Output Spectra & Square Waves   Digital Output Jitter

Low-Level Linearity   Power Consumption

 

These are measured with a $50,000 Rohde & Schwarz UPL laboratory analyzer as calibrated by Rohde & Schwarz.

Unless otherwise noted, all are RMS as measured from the analog output loaded with 200 kΩ at 0 dBFS at 1 kHz. Signals are from the CBS CD-1 test CD as transferred into iTunes as an ALC (Apple Lossless) file, and played via iTunes from a Mac Pro in iTunes 11.1.5 in OS 10.9.4 over a Wi-Fi connection from a much larger home network.

The traces are color coded for the Left Channel and for the Right Channel. When they don't lie on top of each other, it's due to channel imbalance.

 

Output Levels     measurements        top

at 0 dBFS
Volts
dBV
200 kΩ load
1.991 V
5.98 dBV
600 Ω load
1.5885 V
4.02 dBV
300 Ω load
1.3216 V
2.42 dBV

This is the same as a standard CD player (2 V) and 6 dB more than an iOS device (1 V).

 

Output Source Impedance     measurements        top

152 Ω.

 

Noise & DC Offset     measurements        top

 

Noise

Playing digital zeros, 22 kHz bandwidth:

 
Level
SNR*
ENOB**
A-weighted
-97.3 dBV
103.3 dB
16.9 bits
Unweighted
-93.0 dBV
99.0 dB
16.2 bits

* referred to maximum output.

** Effective Number of Bits : (SNR - 1.72 dB) / 6.0206.

I read the same values with iTunes in the Mac Pro paused.

 

Apple AirtPort Express THD

FFT while playing zeros. (CBS CD-1 track 4, R&S UPL.)

 

Apple AirtPort Express THD

Wideband FFT while playing zeros. (CBS CD-1 track 4, R&S UPL.)

 

DC Offset

+1.36 mV left, +3.19 mV right.

 

Channel Balance    measurements    top

The right channel is 0.036 dB lower than the left.

This is marvelous and inaudible. You don't want to know how much "audiophile" gear hits my lab that has its channels out of balance by close to a dB or more, which you can hear.

 

Frequency Response    measurements    top

Apple AirtPort Express THD

Analog output at 0 dBFS, 200 kΩ load. (CBS CD-1 track 11, R&S UPL.)

That's pretty flat.

Yes, it rolls off a bit at the top, and that will make it sound even smoother and warmer. You can pay $3,000 for a 35-pound Sony SCD-XA777ES and engage the special digital filter mode to get the same effect, or just use the AirPort Express.

Let's load it with 300Ω, as if a pair of Hi-Fi headphones were plugged in directly, and see what happens:

Apple AirtPort Express THD

Analog output at 0 dBFS, 300 Ω load. (CBS CD-1 track 11, R&S UPL.)

Aha, a little flatter.

Here's the response measured at the extremes:

Frequency
Response
4 Hz
0.0 dB
8 Hz
0.0 dB
17 Hz
0.0 dB
32 Hz
0.0 dB

.
.
.

.
.
.
2 kHz
0.0 dB
4 kHz
-0.09 dB
8 kHz
-0.29 dB
10 kHz
-0.44 dB
12.5 kHz
-0.66 dB
16 kHz
-1.01 dB
18 kHz
-1.25 dB
20 kHz
-1.54 dB

It's got about the same high frequency rolloff as the special digital filter mode of the Sony SCD-XA777ES, and it's got perfect response to infrasonics.

Here's the frequency response via the TOSLINK optical digital output:

Apple AirtPort Express THD

Digital output frequency response. (CBS CD-1 track 11, R&S UPL.)

Perfect, as expected.

 

THD: 0.003% (-90 dB)    measurements    top

Apple AirtPort Express THD

FFT while playing 1 kHz at 0 dBFS. (CBS CD-1 track 1, R&S UPL.)

 

Apple AirtPort Express THD

Analog output harmonic content, undithered 1kHz sine wave at 0 dBFS. (CBS CD-1 track 1, R&S UPL.)

Ahhh, almost entirely musical second harmonic distortion. Most people have to buy tube amps to get this.

Let's play tracks at low levels and see what happens:

Apple AirtPort Express THD

Analog output harmonic content, undithered 997 Hz sine wave at -20 dBFS. (CBS CD-1 track 18, R&S UPL.)

Perfect, it's got even less distortion at -20 dBFS where it counts. Are we sure there aren't some Nuvistors or a 12AX7 in there?

Let's keep dropping the recorded level:

Apple AirtPort Express THD

Analog output harmonic content, undithered 997 Hz sine wave at -40 dBFS. (CBS CD-1 track 18, R&S UPL.)

 

Apple AirtPort Express THD

Analog output harmonic content, undithered 997 Hz sine wave at -60 dBFS. (CBS CD-1 track 18, R&S UPL.)

Just for fun, let's see how much of this minimal distortion is from the AirPort Express DAC, and how much is inherent in the undithered 16-bit signal:

Apple AirtPort Express THD

TOSLINK digital output harmonic content, undithered 1kHz sine wave at 0 dBFS. (CBS CD-1 track 1, R&S UPL.)

As expected, the digital output has no distortion. For comparison, let's also look at it at -20 dBFS:

Apple AirtPort Express THD

TOSLINK digital output harmonic content -20 dBFS. (CBS CD-1 track 18, R&S UPL.)

Again, no distortion. This was with a recording at -20 dBFS. Let's see if anything changes if we play a 0 dBFS recording and drop the playback level with iTunes slider volume control:

Apple AirtPort Express THD

TOSLINK digital output harmonic content playing 0 dBFS tone with iTunes play volume at -20 dB, 16-bit analysis. (CBS CD-1 track 1, R&S UPL.)

Just for fun, lets analyze the datastream in 24-bit mode and see if Apple is reditheing to 16 bits, or using more bits as the play volume is lowered:

Apple AirtPort Express THD

TOSLINK digital output harmonic content playing 0 dBFS tone with iTunes play volume at -20 dB, 24-bit analysis. (CBS CD-1 track 1, R&S UPL.)

I see no changes; I'll presume only 16 bits are used. I was too lazy to pull out my Tek 764 to see which bits are wiggling or not.

I'm actually measuring the digital datastream itself in a laboratory, no DAC required. This is what comes out of the TOSLINK output, and what a perfect DAC would output.

 

Output Spectra    measurements    top

10kHz   11+12kHz IMD   Square Wave  

Let's see a zoomed FFT of a 10 kHz sine wave. Let's see what sort of spurs surround the carrier, which show us internal jitter:

Apple AirPort Express

Zoomed spectrum of 10,007 Hz 0 dBFS sine wave. (CBS CD-1 track 9, R&S UPL.)

The crud is higher than from a great CD player, but at least there's very little jitter (spreading of the skirts). I can't heat any noise this low, even if a CD player direct analog output might be 30 dB better at this. Bluetooth is horrible by comparison here. Since we can't hear any of this, this is where lossy coding piles the garbage. The AirPort Express uses no lossy coding, so that's why it's so much cleaner than anything via Bluetooth.

Just for fun, let's see if anything changes if we lower the playback level in iTunes:

Apple AirPort Express

Spectrum of 10,007 Hz 0 dBFS sine wave, -6 dB playback level in iTunes. (CBS CD-1 track 9, R&S UPL.)

It's a little better, but not that much. Let's look at the TOSLINK SPDIF digital output:

Apple AirPort Express

TOSLINK output: spectrum of 10,007 Hz 0 dBFS sine wave. (CBS CD-1 track 9, R&S UPL.)

As expected, it's perfect — and precise enough to show that I really use a 10,007 Hz, not 10 kHz, test signal here.

These are super-close-in FFTs looking mostly at jitter. Let's look at it wideband:

Apple AirPort Express

TOSLINK output: spectrum of 10,007 Hz 0 dBFS sine wave. (CBS CD-1 track 9, R&S UPL.)

As expected, the TOSLINK output is perfect.

Here's the analog output in a 110 kHz bandwidth:

Apple AirPort Express

Wideband spectrum of 10,007 Hz 0 dBFS sine wave. (CBS CD-1 track 9, R&S UPL.)

Aha! See the raised noise above 25 kHz? That's where the DAC is putting the noise: up where we can't hear it.

Here's a look at just the audible band:

Apple AirPort Express

Spectrum of 10,007 Hz 0 dBFS sine wave. (CBS CD-1 track 9, R&S UPL.)

 

Let's see how 11+12 kHz IMD look:

Apple AirPort Express

IMD spectrum at 11 kHz and 12 kHz 1:1. (CBS CD-1 track 13, index 2, R&S UPL.)

Much cleaner than Bluetooth! I can't even plot Bluetooth on the same vertical scale. The Sony SCD-XA777ES is better.

Here's the same thing direct from the TOSLINK output:

Apple AirPort Express

IMD spectrum at 11 kHz and 12 kHz 1:1. (CBS CD-1 track 13, index 2, R&S UPL.)

Perfect.

Here it it wideband, from the analog output of course:

Apple AirPort Express

IMD spectrum at 11 kHz and 12 kHz 1:1. (CBS CD-1 track 13, index 2, R&S UPL.)

Nothing troubling here, just some harmonic distortion spikes and shaped noise.

Let's look at square waves:

Apple AirPort Express

1,002.27 Hz 0 dBFS square wave. (CBS CD-1 track 16, R&S UPL.)

This is very good, far better than Bluetooth and better than most outbopard DACS. =what this shows us =is that the AirPort Express won't distort or do anything crazy when playing modern CDs that are recorded at 110%.

Here is is via TOSLINK:

Apple AirPort Express

TOSLINK output, 1,002.27 Hz 0 dBFS square wave. (CBS CD-1 track 16, R&S UPL.)

Perfect, as expected for a direct digital transfer.

Just for fun, let's look wideband at the analog output again:

Apple AirPort Express

1,002.27 Hz 0 dBFS square wave. (CBS CD-1 track 16, R&S UPL.)

Let's reduce the playback level about 6 dB in iTunes and see what happens:

Apple AirPort Express

1,002.27 Hz 0 dBFS square wave. (CBS CD-1 track 16, R&S UPL.)

Aha! That ultrasonic hash, typical in the SACD format, goes away with the playback levels at any reasonable level. Especially if you turn Sound Check ON, you'll never play anything at this foolish a level anyway.

 

Square Wave    measurements    top

Apple AirPort Express

1,002.27 Hz 0 dBFS square wave at full playback level in Mac Pro. (CBS CD-1 track 16, TEK TDS3052.)

This is nearly perfect. A bandlimited square wave is supposed to look wiggly like this, but the edges ought to be a little peakier.

Let's lower the playback volume in iTunes and see what happens:

Apple AirPort Express

1,002.27 Hz 0 dBFS square wave played with Mac Pro volume down a bit. (CBS CD-1 track 16, TEK TDS3052.)

Bingo! Perfection! Few modern digital audio devices can give waveform fidelity like this. Bravo!

 

Digital Output Jitter    measurements    top

Apple AirtPort Express THD

Digital output jitter spectrum. (CBS CD-1 track 1, R&S UPL.)

Aha! As a digital source to feed another DAC, the AirPort express output has even less jitter than the Sony SCD-XA777ES (not that anyone would ever hear this).

This level of jitter is effectively zero.

 

Low-Level Linearity     measurements        top

The 500Hz dithered fade-to-noise test (track 20 on the CBS CD-1 test CD) sounds great out to 24 seconds, or -108 dBFS, when played from an iOS device. Not bad for a 16-bit system!

 

Actual Power Consumption    measurements    top

2.3 W from 120 VAC, regardless of what it's doing.

 

Recommendations         top

Intro   Specs   Measurements   Recommendations

As I suspected, the TOSLINK output is perfect; any audible limitation here is the AirPort's DAC and your source material. As far as I can tell short of comparing bit-for-bit, the optical digital output is a perfect copy of the original, the whole point of digital audio.

The AirPort Express DAC is also very, very good. In some ways it's not quite as good as a $3,000 CD player, and in others it's even better. I'm very happy, this new AirPort Express has much better analog audio quality than the old AirPort Express.

What's superb about this AirPort is that it has a full 2 Volt RMS output, not a whimpy 1 V or less output as we get from the jacks of iOS devices or many other and more expensive outboard DACs.

It's more difficult to set up than Bluetooth, but has no coding loss to affect the audio that Bluetooth does.

At any price, the Apple AirPort Express is a great DAC. It sounds great, with a completely silent background, full 2 V output, smooth detailed sound and full infrasonic bass response.

For best results, leave your player's volume at its maximum for maximum output from the AirPort Express, and then vary the playback level with your Hi-Fi's volume control.

If you find my research helpful, this free website's biggest source of support is when you use these links, especially this link to them at Amazon or at B&H, when you get anything, regardless of the country in which you live.

Thanks!

Ken.

 

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Thanks for reading!

 

 

Mr. & Mrs. Ken Rockwell, Ryan and Katie.

 

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10 September 2014