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Connect DAC with 1 Coax or USB ?

Russm535il

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Hello all !
70 year old long time audio guy here with a quick question. Thank you in advance for your advice . I just bought a new Apple I phone 15 yesterday. I was connecting my previous i11 to my Musical Fidelity V90 DAC with a USB cable from the phone to play Amazon subscription hi res audio . The techs at Apple told me a better connection for sound quality would be to plug the phone into the single coaxial connection on the back of my DAC . I searched on Amazon and found 99% of the phone ( USB-c to coax cables ) had 2 male coax plugs to go into the DAC . I finally found one ( photo ) with one . I don’t understand why most have two and my DAC only has one coax input?
My question is should I just stick with the USB input or purchase the other connector ( i phone to coax input) Thank you! I spent about three hours last night on the Internet, trying to figure out an answer and could not find one. Best ! Russ Dejulio Pittsburgh PA
 

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Technically those are not coax plugs, but phono / RCA plugs.
The term is often used interchangeably with DACs, because it's a coaxial connection using a phono (RCA) plug and socket.
It would seem that the other cable you describe with two coax (phono / RCA) plugs, is a typical audio interconnect however it's difficult to say for sure without knowing exactly which connectors were on both ends of the cable, however if it was USB C to 2x RCA then it sounds as though it's some sort of DAC.
Was it this cable (or one like it?).


If so, that cable contains a DAC.
 
I'm not an Apple guy...

I wouldn't expect any difference. It's all digital and it's all the same bits & bytes. (An optical connection can remove a ground loop but you are unlikely to have ground loop problems from a phone.)

...As a rule, the digital-side is not an issue. Audio quality is mostly on the analog-side, especially speakers, headphones, and room acoustics. Any digital errors tend to be gross & obvious* (loud clicks & pops or gaps-dropouts in the audio).


* This is an imperfect analogy but one flipped-bit in your bank account is equally likely to cause a billion dollar error or a 1-cent error.
 
Last edited:
Coax S/PDIF has no inherent advantage over USB.

If USB works, then use that.
 
Technically those are not coax plugs, but phono / RCA plugs.
The term is often used interchangeably with DACs, because it's a coaxial connection using a phono (RCA) plug and socket.
It would seem that the other cable you describe with two coax (phono / RCA) plugs, is a typical audio interconnect however it's difficult to say for sure without knowing exactly which connectors were on both ends of the cable, however if it was USB C to 2x RCA then it sounds as though it's some sort of DAC.
Was it this cable (or one like it?).


If so, that cable contains a DAC.
The cable that I took a photo of below was what the Apple techs recommended it’s for sale on Amazon
 
Hello all !
70 year old long time audio guy here with a quick question. Thank you in advance for your advice . I just bought a new Apple I phone 15 yesterday. I was connecting my previous i11 to my Musical Fidelity V90 DAC with a USB cable from the phone to play Amazon subscription hi res audio . The techs at Apple told me a better connection for sound quality would be to plug the phone into the single coaxial connection on the back of my DAC . I searched on Amazon and found 99% of the phone ( USB-c to coax cables ) had 2 male coax plugs to go into the DAC . I finally found one ( photo ) with one . I don’t understand why most have two and my DAC only has one coax input?
My question is should I just stick with the USB input or purchase the other connector ( i phone to coax input) Thank you! I spent about three hours last night on the Internet, trying to figure out an answer and could not find one. Best ! Russ Dejulio Pittsburgh PA

The apple dongle has an internal converter and has a 3.5mm TRS stereo jack. When you use that you will not be using (actually it will be replacing) the V90 DAC and you will need a 3.5mm TRS jack to 2xRCA connector into your amp.

The iphone 15 has a USB-C output which you can connect to your V90 DAC and use it like you did before.
For this you need to buy an USB-C to USB-B cable.
 
Both solutions would probably work fine.... Didn't look closely at the right picture and thought it was apple dongle. :facepalm:

One is USB-C to SPDIF (RCA) and the other solution USB-C to USB-A contra.
Might be best to use USB-C to USB-B cable perhaps.
 
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