Review and measurements of MacBook Air (2024) headphone output

[mcdn]

I believe so, as long as 1.0 V is sufficient (and I think it's *on* topic).

That’s correct, output is only 1V, which is good for most active speakers but might be a bit low for separate power amps.

 

[AudioSceptic]

That’s correct, output is only 1V, which is good for most active speakers but might be a bit low for separate power amps.

There seems to be a standard for pro audio and I know that some Linn power amps needed only 1 V for max output power. I wonder how common that is.
I got this from a browser search:
"
The input signal required for a power amplifier to achieve its maximum output power depends on its input sensitivity. For professional audio equipment, a typical line level is +4 dBu, which corresponds to 1.23 Vrms. However, signal peaks can exceed this level by 20 dB or more, reaching up to +24 dBu.1

Most power amplifiers are designed to handle an input sensitivity of +4 dBu, meaning they will clip if fed a higher voltage. Some amplifiers offer adjustable input sensitivity settings, such as the Bose PM series, which can handle input voltages up to +24 dBu.1

For consumer audio equipment, the output voltage from a preamplifier or processor is usually lower, around 1 Vrms or less. This can be insufficient to drive a professional power amplifier to its full output voltage, leading to potential clipping issues."

 

[Marc v E]

This is a review and measurements of the MacBook Air 2024 headphone output. It was prompted by a request from @DrSpan, as the little Mac has a very strong reputation as a headphone source. Here it is, measuring itself:

View attachment 454294

Since 2021 Apple has supported impedance detection on the headphone outputs of its laptops, meaning low impedance headphones get more current, while high impedance headphones get more voltage. When you plug in the headphones the MacBook checks the impedance, and sets the output voltage to 1.25V if it's less than 150ohms or 3V if it's up to 1kOhms/. Above that it assumes you're using it as line interface and sets the voltage to 1V. It only does this check when you physically plug in the jack, which caught me out a couple of times in testing!

So the first question is does the impedance sensing work? It absolutely does, and the voltages are superbly accurate at 1.00V (4.7kOhms) and 1.25V (30ohms), dropping a tiny bit from spec to 2.97V at 300ohms.

The second question people have is how much power it can actually deliver? I won't make you wait, it delivers exactly to spec into 300ohms at 29mW, so essentially no voltage drop. Into 30ohms I got 48mW against an ideal of 52mW, and into 15ohms the gap widened a bit more with 85mW against an ideal of 104mW.

OK, let's do some graphs! The measurements were taken with a Cosmos ADCiso and a resistive dummy load. The ADC was running at 96kHz/24bits, with the laptop outputting 44.1kHz/float32, which is the default. The laptop was connected to external power via a thunderbolt hub. The headphone output itself is a 3.5mm TRS jack, i.e. unbalanced stereo.

Here's the best SINAD I could get, which was at 0dBFS output into 30ohms, delivering a SINAD of 97.9dB:

View attachment 454454
Frequency response is ruler flat to 16KHz, then drops about 6dB by 20KHz. If you change the output sample rate in "Audio MIDI setup" then you get the same result, e.g. the drop starts around 44kHz when using a 96kHz sample rate. The good news is the filter is steep and clean with no rise in noise after. It does look quite tailored, but I didn't get into impulse tests:

View attachment 454290

Here's THD+N vas power at 15, 30 and 300ohms:
View attachment 454286

And here's CCIF IMD (19 and 20kHz tones) at 30 and 300ohms:
View attachment 454287
The multitone distortion is very clean - I've overlayed all three impedances but they are pretty much the same:
View attachment 454288
Crosstalk was about -50dB. This was measured by driving one output at 0dB while measuring the other, so they share about 1m of cable before being split out for measurement:
View attachment 454289

At 50mV into 30ohms (with the Cosmos Scaler boosting the signal to about 1V into the ADC) I was able to get a SINAD of 89.1dB, which is less than the 95dB L7 Audio Lab measured but I think their measurement may be A weighted, and they have an APx555:
View attachment 454453

In conclusion definitely 5 quokkas from me! There's simply no reason to use an external headphone amp with any MacBook made since 2021 unless you have demanding headphones. It's not nearly as good for power as a good desktop headphone amp, but it is better than popular interfaces such as the Scarlett 2i2.

Thank you!

I had a sneaking suspicion macbooks are pretty good as music source and headphone amp by daily experience working from home.

 

[Ismapics]

This is refreshing with the ever elimination of ports on PCs and Smartphones, to read this is really encouraging. Also as I will try and test right now here as I have the same MacBook Air right here. Looking forward to a little music in a few minutes.

 

[AudioKC]

Great review. Thanks! Basically the same performance as Apple Dongle, as far as I can understand.

 

[staticV3]

Great review. Thanks! Basically the same performance as Apple Dongle, as far as I can understand.

With the exception of much higher output voltage.

High impedance headphones from Beyerdynamic, Sennheiser etc can play twice as loud as with the Apple dongle (thrice as loud when comparing to the EU dongle)

 

[AudioKC]

With the exception of much higher output voltage.

High impedance headphones from Beyerdynamic, Sennheiser etc can play twice as loud as with the Apple dongle (thrice as loud when comparing to the EU dongle)

Thank you!

Asked perplexity if Mac mini M4 has the same performance, with high probability answer is "Yes". Link to the answer

Question is not just a "curiosity", I run my DCA Noire 2 from it

 

[Ron Texas]

I have an M3 MacBook Pro. It drives Senn 650's easily.

 

[jkim]

Is its DAC/amp circuit likely based on a Cirrus Logic chip?

 

[staticV3]

Is its DAC/amp circuit likely based on a Cirrus Logic chip?

Yes.

 

[jkim]

Yes.

Referring to this? Or any other source?

 

[dasdoing]

They certainly have some of the best engineers

half work for, the other half against their customers rs

 

[lewdish]

Anyone able to confirm if the Air models have a high impedance auto mode? I feel like i recall the pro models having it but the air seems rather weak in the power output department, that being said it is the more "affordable" model

 

[Scrivs]

It's in the title, Brosef

 

[caocaolatre199x]

Very good but it seems to be the same as LG phones. I don't like its automatic impedance detection mode. For headphones with low impedance and low sensitivity, it simply won't be able to get the most out of such headphones. So in my opinion it's very good but not optimal.

 

[Steve356]

I have an M3 MacBook Pro. It drives Senn 650's easily.

Same for me with a M1 MacBook and 650s.

 

[mcdn]

Anyone able to confirm if the Air models have a high impedance auto mode? I feel like i recall the pro models having it but the air seems rather weak in the power output department, that being said it is the more "affordable" model

I linked in the first paragraph to the Apple support page which details all the models that have this mode.

The voltages are the same across all models so no, the pro MacBooks don’t have more power.

The output is really clean up to full output, so if it’s loud enough for you with your headphones then stop and enjoy.

If it’s not loud enough then you probably need a desktop headphone amp, although some dongles also qualify.

 

[mcdn]

Very good but it seems to be the same as LG phones. I don't like its automatic impedance detection mode. For headphones with low impedance and low sensitivity, it simply won't be able to get the most out of such headphones. So in my opinion it's very good but not optimal.

If it’s not loud enough for your phones then you’ll need an external amp for sure. But it will play clean up to its limit.

 

[norcalscott]

Very good but it seems to be the same as LG phones. I don't like its automatic impedance detection mode. For headphones with low impedance and low sensitivity, it simply won't be able to get the most out of such headphones. So in my opinion it's very good but not optimal.

Are you aware of the trick to plug a headphone extension cable in (no headphone connected) and the LG phone will detect high impedance? Then plug your headphones in. Works great on my beloved LG G7, which I now use a dedicated DAP.

 

[jkim]

I couldn't help but measure my 2024 MacBook Air's audio output.

I would not have posted the results in a new thread if what I found had no new information beyond what was observed in the OP's review or L7 Audio Lab's. But my hunch was correct. The Cirrus Logic chip inside MacBook produces very interesting behavior which I dubbed a "Cirrus hump" in a sweep of multitone tests. It turns out that it's even more drastic than observed from devices based on CS43131/CS43198.

See my measurements here:

Test of "Cirrus Hump" Distortion of Apple MacBook Air Audio Output

After writing my recent review, "On the Distortion of Cirrus Logic CS431xx-Based Devices: A Comparative Review", I wondered if the same anomaly exists in other electronic devices that rely on Cirrus Logic D/A converter (DAC) chips, in particular Apple MacBook products that still provide analog...

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