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Comment by rusk | Hacker News Reader

Here's a quick note on bluetooth/digital sound quality, from recent experience.

I'd been playing music on my car stereo (Kenwood, nothing amazing) across bluetooth. I finally got around to picking up a lightning cable to connect directly for charging but thought I'd try playing music across it.

I was instantly struck by how much better the sound quality was.

I don't think the sound output in this case is digital am I right? Lightning still supports analogue output equivalent to the headphones jack for these usecases?

So we're being sold on this idea that digital/bluetooth is "better" but as somebody else points out here that's purely down to the DACs that are in use, but from my personal experience the DACs native to the iPhone are actually pretty good.

I wonder, apart from other motives proposed here, is eventually eliminating expensive analogue circuitry from the iPhone BOM a part of what's going on here?

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Bluetooth audio itself uses digital compression to keep the bandwidth low, and has a whole bunch of optional codecs (https://en.wikipedia.org/wiki/List_of_Bluetooth_profiles#Adv...). Your Kenwood may not support the higher quality codecs, meaning it would sound worse than a comparable headphone jack aux cable.

Even the best codecs used for BT audio are lossy, aren't they? So wouldn't an aux or lightning connection always sound better?

I think that's the point he's making.

I don't think it is? He said:

> Your Kenwood may not support the higher quality codecs, meaning it would sound worse than a comparable headphone jack aux cable.

That implies there's BT audio codecs that sound the same (or I guess better, but I think he/she probably meant "same") as an aux cable. I was saying I don't think that's true, that even the best BT audio codecs are (noticeably) inferior to in-phone-DAC-to-analog connections.

Sorry yeah missed out on the "best" audio codecs part of your predicate, as if to say "the ceiling is lower than you think" - sorry

It's a shame that Bluetooth can't do something like a stream copy. Quality could be better if your phone could pass the raw mp3/vorbis/opus stream over BT. Even with HQ codes like aptX it's pretty silly to be converting 256k mp3 to aptX at similar or higher bitrate.

Isn't that Bluetooth file transfer? Good idea but I guess the idea of a streaming protocol is it addresses realtime concerns in an unreliable medium. Imho that's the kind of thing analogue coding schemes are better at.

If it can output 320kbps MP3 or equivalent, nobody's gonna notice unless you tell them.

Of course this is correct if you being with a lossless file, but if you start with an already lossy file, despite it being possible to sound the same as a lossless file, when you re-encode it with a different encoding, for example ogg -> mp3, you'll lose different parts of the file in the compression algorithm, so it will end up sounding worse.

I can't say I know how the different bluetooth audio codecs work of course.

Just because it's lossy doesn't mean it can't sound good, but sure aux and lightning are probably better choices if you're concerned about it sounding good.

The huge audio difference described above is atypical from my experience, so I'd blame the stereo's bluetooth support before bluetooth audio itself.

I'm pretty sure the lightning standard doesn't support an analogue signal at all, hence the role of the adapter as a DAC. Around 23mins in the linked video you see the part he's using inside the phone, and it seems more complex than simply matching pins.

In terms of your car stereo, I'd say that'd be an internal DAC, and the quality difference was simply down to a physical connection compared to Bluetooth(probably a previous standard too, the jump from Bluetooth 4.0 to Bluetooth 5.0/W1(as in AirPods) is pretty similar in magnitude to the jump from USB 2 to USB 3/Lighting(Lightning was again Apple adding support for modern features before the standard was finalised)). In the same way that nobody would've seriously dropped a dedicated display port before USB 3, the new Bluetooth standards are opening up audio to replace physical connections.

As I understand it, Apple ultimately ended up dropping the headphone jack due to interference(the DAC was being interfered with) from some internal components in the new design, as well as making waterproofing easier. I'm fairly certain there's no DAC already at this point.

Sorry I should have done a bit more research before posting ... yes it appears that the official line on lightning is that it's digital only, but there are conflicting empirical accounts [0]

Since my 5s still has a headphones jack there is certainly still a DAC there.

It could well be down to the fact that my car stereo has a better DAC on the USB line than it does on the bluetooth line. Or simply an older bluetooth audio standard as you suggest. Actually this is probably the most likely suspect!

Which I think all serves to underline how digital output is not "open and shut" when it comes to sound quality.

Thanks for the additional technical context on why they might be eliminating analogue signal altogether. I'd felt a similar rationale informed their refusal to include a FM receiver from the beginning.

It does make sense from many different perspectives for apple to make this "not their problem". I kind of feel it's a pity from a customer/functional perspective though.

[0] https://www.innerfidelity.com/content/apples-lightning-headp...

>I'm fairly certain there's no DAC already at this point.

The iPhone still has a physical speaker, doesn't it? Therefore there must be one.

Doesn't mean it's connected to the lightning port - and in fact it's not.

what's that got to do with anything?

It probably means that the iPhone 7 can't output analoge signals via the Lightning port, so thre must be a DAC inside the 3.5-to-lightning adapter.

Bluetooth honestly isn't better yet. They should've waited to remove the headphone jack until Bluetooth 5 headsets were out (same bandwith, but much lower power, easier pairing and much better compression). It would've made some sense.

I'm guessing that they thought the headphone was interfering with their design for iPhone 8, and that they wanted to take the PR-hit with the 7. They were in the loop about the Bluetooth 5 spec, so for them it made sense, even if it's too early for consumers.

Its not the DAC, BT Audio uses ancient horrible low bitrate codec

Agreed, cable is much much better quality. Not sure what the reason is though...

crappy dacs on commodity bluetooth audio devices?

somebody else pointed out the more established bluetooth digital audio standards aren't as good. This may well be the reason.

Bluetooth audio is typically loss-ily re-encoded due to limited bandwidth and has sounded really bad in the implementations I've tried (an iPhone connected to earbuds and a Toyota Prius).

I've had a hard time finding out technical details of Apple's new w1 chips - what increased bandwidth they support, if any. This one case where Apple hiding the tech specs from consumers is pretty irritating.

I'm no audiophile pushing for nonsense like 24/192 downloads, but I do care about music enough to actively avoid overly-compressed audio via bluetooth or Sirius/XM as the sound is grating.

I'm thinking Bluetooth 5.0 will solve this quality issue, but I'm certain there is somebody with actual domain knowledge in this thread to enlighten.

Edit: link to some reference on bluetooth quality http://www.sereneaudio.com/blog/how-good-is-bluetooth-audio-...

What I'll actually do, since my stereo actually has a headphones line is a qualitative comparison between the headphones jack, usb and bluetooth and I'll get back to you.

This seems like a pretty small set of data to base your conclusion on. Anyway, if fidelity is the concern, most new cars support just directly plugging in your phone via USB.

It's hardly data, it's personal experience. Seems the main thrust of your argument is that if I spend a load of money I'll get better results. Well Duh

Well, no, the main thrust of my argument is that if the primary concern is data fidelity then sticking with a headphone jack seems silly.

But the thrust of my argument was that bluetooth was inferior to a wired connection (and probably inferior to analogue from the jack itself). As other commentators have helpfully pointed out this is due to the poor codecs in use with bluetooth. So there's plenty of extraneous contributed "data" that supports my claim.

But a wired connection is hardly unsupported, regardless. The funny connector seems like a nonissue for a car.

There you are putting words in my mouth. I never made any remark about the connector. It's almost like you came to this discussion with a point to disprove already in mind.

I figured "the aux connection has better fidelity than Bluetooth" was meant to imply "they should keep the headphone jack."

nope it was just meant to imply that the sound quality was better (-:

Alright, fair enough.

More directly to your point, though, I've never experienced problems like one speaker cutting out because the wire is too old with digital connections. I really like digital better because it's mostly either working or not.

Oh but ...

My big gripe with digital vs analogue is it's all or nothing. When digital degrades its unbearable to listen to. Analogue handles age more gracefully.

I guess I don't like being slowly driven insane wondering if some degradation is just in my head, jiggling the wire, etc. Maybe just me.

I don't think so. AFAIK the lightning connector is fully digital and the D/A convertor is only in the adapter.

I'm on a 5s though. I still have the headphones jack.

That doesn't mean your lightning connector is capable of putting out analog audio, it just means your headphone jack does.

AFAIK the lightning connector is fully digital and the D/A convertor is only in the adapter

Clearly not so if I've got a jack ...

if the DAC only exists between the logic board and the analog jack then there is a good chance it isn't being piped back in to the lightning port. Even then, I really doubt an entire pin on the lightning connector is dedicated to analog signal, so a DAC would have to exist on the other end of your lightning cable anyway; I suspect this is where your difference in quality come from.

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