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iPhone -> Lightning/USB 3 adapter ->DAC is it bit perfect?

Akedon

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Hello, recently tested iPhone with my preamp (Rotel RC-1590). Streaming service - Apple Music.
If I connect iphone to preamp via lightning-usb charging cable to the front USB-A input - I'm getting 44.1khz max sample rate, iphone charging, but iphone also can't control volume.
If I connect iphone to preamp via back USB-B input with this chain (iPhone -> Lightning/USB 3 adapter -> USB A - USB B -> Rotel) I'm getting up to 192 khz (as it shows in my preamp), but I can control volume from iphone and also I hear sounds from iphone (when you tapping on keyboard for example) on my speakers.
Is it actually bit perfect or the sound is going through the iOS mixer first?
 

Martinvb

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Hello, recently tested iPhone with my preamp (Rotel RC-1590). Streaming service - Apple Music.
If I connect iphone to preamp via lightning-usb charging cable to the front USB-A input - I'm getting 44.1khz max sample rate, iphone charging, but iphone also can't control volume.
If I connect iphone to preamp via back USB-B input with this chain (iPhone -> Lightning/USB 3 adapter -> USB A - USB B -> Rotel) I'm getting up to 192 khz (as it shows in my preamp), but I can control volume from iphone and also I hear sounds from iphone (when you tapping on keyboard for example) on my speakers.
Is it actually bit perfect or the sound is going through the iOS mixer first?
Don’t see why not. IMO this is the only route to export HiRes (> CD quality) audio signal from iPhone to an external DAC.
 
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Akedon

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Don’t see why not. IMO this is the only route to export HiRes (> CD quality) audio signal from iPhone to an external DAC.
I mean is that normal that I can change volume from iPhone?
 

DimitryZ

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I mean is that normal that I can change volume from iPhone?
Good observation. I set the volume to max on the iPad and the setup triggers MQA recognition on Gustard X16, suggesting bit-perfect.

I will lower the volume and see if above changes.
 
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Akedon

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Good observation. I set the volume to max on the iPad and the setup triggers MQA recognition on Gustard X16, suggesting bit-perfect.

I will lower the volume and see if above changes.
Probably at max volume it will be bit-perfect, but I can't check it with my DAC, only sample rate is showed.
 

DimitryZ

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Probably at max volume it will be bit-perfect, but I can't check it with my DAC, only sample rate is showed.
I can report that in Qobuz and Tidal the iPad's volume rocker is disabled.

This strongly suggests bit-perfect - IOS equivalent to Windows WASAPI connection.
 
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Akedon

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I can report that in Qobuz and Tidal the iPad's volume rocker is disabled.

This strongly suggests bit-perfect - IOS equivalent to Windows WASAPI connection.
Yep, that's how it should work.
Strange that with rear USB-B input of my preamp (connected via Lightning/USB 3 adapter) iOS is not locking volume, but changing sample rates properly. I'm using iPhone 7+ with last updates.
With front USB-A via Lightning - USB A it locks the volume at max, but also it locks sample rate at 44.1khz...

Your iPad connected to DAC with an adapter or straight with charging cable?

Also checked mConnect app (which can stream Tidal and Qobuz), audio path says "iPhone ->USB Audio", so I'm not getting bit-perfect probably.

Looks like only what I can try is test it with another iPhone (I can test it with iPhone X), or test it with this cable, so I can connect it straight to DAC without adapters.

UPD: tested with Iphone X - same behaviour.
 
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Akedon

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I recently did some testing when I compared Tidal and Apple Music, so I will paste it here too.

Tested closely Tidal and Apple Music at high volume

Audio chain iPhone ->CCK->Rotel RC-1590 preamp (USB-B input)->Rotel RB-1590 amp->Polk Audio RTi A9 speakers
Native apps.
Used the same songs from the same albums. Usually both 44.1 khz 16 bit (you can check tracks from Tidal with mconnect app - it shows codec and bitrate of Tidal streams), sometimes 24 bit on Apple Music. Flac files from Tidal and ALAC files from Apple Music.
Same volume level on my preamp.

I said before that Tidal with my rig sounded slightly better, but I didn't listened closely, so listened to it for ~2 hours. Well, at high volume Tidal sounded much better. Apple Music for some reason sounds distorted/harshy at high volume, while with Tidal stream I can stand very close to my loud tower speakers and can even raise volume level further - it's still super clear, my ears still not bleeding, but it's VERY loud - louder than the same track from Apple Music.
Also, Apple Music has some stutters when playing music, while Tidal playing without any interruptions.

At first I really wanted Apple Music to be the winner for this test since I like Apple's big library with solid amount of tracks with cd+ quality. I actually have no idea why there is so big differences, but that's it - Tidal is the absolute winner in sound quality compared to Apple Music. At least on iOS.
 

DimitryZ

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I recently did some testing when I compared Tidal and Apple Music, so I will paste it here too.

Tested closely Tidal and Apple Music at high volume

Audio chain iPhone ->CCK->Rotel RC-1590 preamp (USB-B input)->Rotel RB-1590 amp->Polk Audio RTi A9 speakers
Native apps.
Used the same songs from the same albums. Usually both 44.1 khz 16 bit (you can check tracks from Tidal with mconnect app - it shows codec and bitrate of Tidal streams), sometimes 24 bit on Apple Music. Flac files from Tidal and ALAC files from Apple Music.
Same volume level on my preamp.

I said before that Tidal with my rig sounded slightly better, but I didn't listened closely, so listened to it for ~2 hours. Well, at high volume Tidal sounded much better. Apple Music for some reason sounds distorted/harshy at high volume, while with Tidal stream I can stand very close to my loud tower speakers and can even raise volume level further - it's still super clear, my ears still not bleeding, but it's VERY loud - louder than the same track from Apple Music.
Also, Apple Music has some stutters when playing music, while Tidal playing without any interruptions.

At first I really wanted Apple Music to be the winner for this test since I like Apple's big library with solid amount of tracks with cd+ quality. I actually have no idea why there is so big differences, but that's it - Tidal is the absolute winner in sound quality compared to Apple Music. At least on iOS.
Did you disable Atmos in Apple Music settings?

In my experience, Atmos-rendered music doesn't sound good into a standard 2 channel playback.
 
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Akedon

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Did you disable Atmos in Apple Music settings?

In my experience, Atmos-rendered music doesn't sound good into a standard 2 channel playback.
Dolby Atmos disabled, EQ disabled, Sound check disabled.
Strange things.
I think something is wrong with the iOS or Music app in my situation. mConnect and Tidal sounded the same without any issues probably because they are do not depend on iOS music settings (which should be fine on paper since I disabled everything except lossless quality, but it's still doing something).
 

DimitryZ

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Let me check. I haven't listened to Apple Music for a while. I have Tidal and Qobuz on the same iPad, so I can compare.

What tracks did you find to show the Apple/Tidal difference more?
 
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Akedon

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What tracks did you find to show the Apple/Tidal difference more?
At high volume and if you are standing close to the speaker - pretty much every track. But some active and dynamic electronic/metal shows bigger differences. Like "Mental Exile - One of us", "Ashbury Heights - Headlights", "Rammstein - Sonne" (tested this with local flac file since i don't have Rammstein on Tidal).
 

DimitryZ

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At high volume and if you are standing close to the speaker - pretty much every track. But some active and dynamic electronic/metal shows bigger differences. Like "Mental Exile - One of us", "Ashbury Heights - Headlights", "Rammstein - Sonne" (tested this with local flac file since i don't have Rammstein on Tidal).
On my system, Apple Music sounds fine. I also can't change the volume, just like Tidal and Qobuz, implying bit-perfect transmission.

Are you using this thingy for connection,?

Apple Lightning to USB3 Camera Adapter https://smile.amazon.com/dp/B01F7KJDIM/ref=cm_sw_r_apan_glt_i_HFDB9J40X8BXY4VB81Q1
 
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Akedon

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On my system, Apple Music sounds fine. I also can't change the volume, just like Tidal and Qobuz, implying bit-perfect transmission.

Are you using this thingy for connection,?

Apple Lightning to USB3 Camera Adapter https://smile.amazon.com/dp/B01F7KJDIM/ref=cm_sw_r_apan_glt_i_HFDB9J40X8BXY4VB81Q1
Thank you for testings.
Yes, I'm using exactly this camera kit. Can change the volume everywhere, but for some reason only Apple Music sounds wrong.
Checked with other iPhone - same things.
Asked on another topics/forums - someone said he can change the volume, soneone said he can't. Looks like it depends on a DAC used.
I will check it with Lightning - USB-B cable (without CCK) when it arrives and we will see.
 

DimitryZ

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Thank you for testings.
Yes, I'm using exactly this camera kit. Can change the volume everywhere, but for some reason only Apple Music sounds wrong.
Checked with other iPhone - same things.
Asked on another topics/forums - someone said he can change the volume, soneone said he can't. Looks like it depends on a DAC used.
I will check it with Lightning - USB-B cable (without CCK) when it arrives and we will see.
Maybe there is an IOS setting that needs attention?

I have a bunch of DACs and they all seem to act the same connected to an iPad.

I will cycle through them to make sure.

The only difference in our setups is that I use a switchable powered USB hub to direct the digital signal to several DACs.

Universal 8-Port Powered USB 3.0/USB C Hub, Aluminum USB Splitter with 6 USB 3.0 Data Ports, SD/TF Card Readers, On/Off Power Switches, AC Adapter, for PC, Laptops, MacBook Pro/Air, Surface Pro, HP https://smile.amazon.com/dp/B085Q2H...t_i_4NYF46C7XE6AW9JNCBGD?_encoding=UTF8&psc=1
 
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Crunchynut

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I have used that set-up iPhone >Apple Music >CCK>DAC, and for me the volume control on the iPhone locks out. (iPhone 12 mini).

I also use an iPad mini 6 which uses USB C. A different CCK but same effect - locks out the volume.

DAC in both cases is RME ADI-DAC 2 FS


Curious about your lightning to USB B cable. I would be nervous about what is going on in such a cable. Is there a chip? If so what is it doing?

The thing is, lightning is not USB standards compliant, which is why some devices won’t talk to an iPhone unless the CCK is used - the CCK is more than a gender changer - it contains chips to do the conversions to USB standards.

For my iPad, I bought some USB C to USB B cables, until I learnt that USB C cables needs chips in them (basically to re-map the pins in the lead because the lead can be inserted either way round). That made me nervous in terms of ‘what are the chips doing to my bit perfect aspirations?’. So I now use the Apple USB-C AV adapter (which is like the CCK for lightning) to give me a USB A output from the iPad, from which I can use a dumb USB A to B lead, and know that any conversions are genuinely catered for by Apple designed electronics.

Sorry if you know all this - but hopefully others may find these details useful.
 

DimitryZ

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Maybe the issue is Rotel's USB input?

DAC is supposed to claim IOS equivalent of WASAPI - the volume is disabled.

I will check all of my DACs - I remember that one of them allowed me to control volume on the iPad, just can't remember which one.

Added: I can report that my DACs that allow for volume control on the iPad are:

1. Modern unit built around a vintage AD1865 DAC, with XMOS108 USB board.
2. Musician Pegasus
3. SMSL M300

At full iPad volume they certainly all sound undistorted with Apple Music.

Gustard X16 and Oppo UDP-205 lock out the volume on the iPad. Both sound undistorted.
 
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AKR

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I have a question on connecting my iPhone/iPad wired to a DAC ( not portable) using a lightening to USB C cable with a that comes with the phone/iPad. I have read conflicting reports of folks having success with this and others saying you need the Apple camera connection kit to pass audio from the lightening port. Has anyone had success with this without using the Apple CCK ?
 

Crunchynut

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This is my understanding.

Lightning port is not strictly USB standard compliant, so it depends on how sensitive the DAC is to the source adhering to the standard or not. That’s why the camera adapter is advised because it is not just a wiring adapter - it does actually take the non-standard lightning and turn it into standard USB and hence will (should) work with all USB input DACs.

On newer Apple products that use USB C instead of lightning, then that output is USB standard compliant. However USB C is a whole other world of complexity because of the chips needed in what look like standard USB leads to cope with the fact the connector works either way up, and to do with the extra power C can support. So, in my case, rather than use a USB C to USB B lead from iPad to DAC, with no certainty about what the chosen (generic made in China somewhere) cable is doing to my signal, I still use the camera kit (or video adapter as it is now called) to give me a standard USB A output, from which I use a standard (no intelligence) A to B lead.
 
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AKR

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This is my understanding.

Lightning port is not strictly USB standard compliant, so it depends on how sensitive the DAC is to the source adhering to the standard or not. That’s why the camera adapter is advised because it is not just a wiring adapter - it does actually take the non-standard lightning and turn it into standard USB and hence will (should) work with all USB input DACs.

On newer Apple products that use USB C instead of lightning, then that output is USB standard compliant. However USB C is a whole other world of complexity because of the chips needed in what look like standard USB leads to cope with the fact the connector works either way up, and to do with the extra power C can support. So, in my case, rather than use a USB C to USB B lead from iPad to DAC, with no certainty about what the chosen (generic made in China somewhere) cable is doing to my signal, I still use the camera kit (or video adapter as it is now called) to give me a standard USB A output, from which I use a standard (no intelligence) A to B lead.
Thank you. Very clear. I confirmed the direct connection to my DAC does not pass audio- it just plays on the phone so iOS is not even transmitting it.
 
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