[musickid]

BASIC SOUND SCIENCE HELP NEEDED: could you all be kind enough to read through the following and tell me if im correct on all three points. im new to this relatively speaking. many thanks. MK. The first part from a fellow headfier.
 
 
"No idea. I have never used that DAC. Audio Midi Setup should allow you to choose the format at which you send data to the DAC and allow you to pick a different format. You will have no idea what the DAC does with the data unless you read the DAC docs are ask the DAC manufacturer support team.
 
I know that my DAC upsamples or downsamples everything to 24/176.4 or 24/192 if the format is different that one of those two. If the DAC is fed 24/176.4 or 24/192, no upsampling or downsampling is done. My DAC is particularly good at upsampling/downsampling so I send it the music in whatever format it is in natively. Audirvana changes the format on the fly. In other words, Audirvana does no upsampling or down sampling. The DAC does it all. Not all players do this."
 
MY RESPONSE:
 
 
1) i always thought that the sample rate for the dac i choose in audio midi set up on my imac is the sample rate the dac will then use to process the digital audio. so for example if i choose 44.1khz/16 bit in audio midi set up i am in fact directly affecting the hardware in the dac to sample at this rate. but from your explanation the sample rate in audio midi set up is actually the format at which data is sent to the dac? am i right here? i fear i've been mistaken on this point till now. as you say you can't tell the upsampling or downsampling rate of the internal working of the dac unless you refer to manufacturer's details. so if tidal lossless file sample is 44.1/16 i just set that in audio midi set up and now the computer sends the digital audio to the dac in exactly the same format as it is natively from tidal? im on a really steep learning curve and grateful for your help. if everything ive written above is totally correct could you confirm that please.
 
2) the breeze du u8 is a usb to spdif convertor not a dac which will show up as the audio output device in audio midi settings. the dac wont show in this case. i wanted to know do i again just set the sample rate to match the native sample rate of the digital audio coming in from tidal? ie 16/44.1 unless tidal has exclusive control of the device then it does it automatically? ie tidal controls the format at which data is sent to the convertor in this case?
 
3) with both of the above devices only with the dac you yourself are using in this example do you know that upsampling or downsampling occurs to 176/192 unless it is fed 176/192 where no up or down sampling as you say is done. with the convertor (ddc) you can never tell what final sample rate the coax output digital audio will be unless you study the manufacturers details or the convertor has a digital readout to tell you? here you can only adjust the format at which data is sent to the convertor in audio midi set up again to match the native format of the tidal digital music file. (i use tidal hifi for most of my listening.) thanks for your patience here.
 
id be grateful if you could confirm points 2 or 3 are correct or incorrect. many thanks again for your help. mk

 

[castleofargh]

moved as it had nothing to do with RMAA. if you wish for another title just let me know.

 

[RRod]

I'm not as well versed in MAC audio as Linux audio, but I'll give it a shot:
 
Audio MIDI Setup determines the format to output to the DAC, which is why the drop-down selections are limited to those supported by the DAC. A given sound program might output in a format different from this. It is thus the job of the CoreAudio to change the format coming out of the sound program into the format selected for the DAC.
 
If you want "bit-perfection", everything needs to match.

 

[Roseval]

  the sample rate in audio midi set up is actually the format at which data is sent to the dac?

Completely correct.
A lot of DACs do convert internally e.g. Benchmark DAC 1 converts everything to 110 kHz
Upsampling DACs often to 192
 
Common is to match the PC settings with the sample rate of the audio to avoid a double re-sampling.
However, the SRC of OSX is quit good, one might wonder if it is audible.

 

[musickid]

hi roseval,
 
could you let me know what you think of the following,
 
Ive joined this forum to try and find the answer to a question that i cant find elsewhere. i use an external digital to analogue convertor (dac) with my imac late 2013 27inch. the dac is linked to a dedicated headphone amplifier. i want to be 100% sure that the clock in the dac is the one being used and NOT the macs clock. i use usb out of mac with a usb to spdif (coax) convertor to the dac. here's the problem.

very simply in audio midi set up there are two options for controlling the dac. one reads clock source default and is greyed out. here you can alter the sample rate and bit rate. the other option is to add the dac as an aggregate device. here the clock source now reads out the name of the dac but i think you now only alter the sample rate not the bit rate. i like the fact here that the dac shows up in clock source but i am still not sure which option is correct to ensure it is the dac clock which ultimately gets used and not the clock in the computer. or am i off target here? do both of the above options lead to the dac being in full control. i appreciate your help. after many enquiries i still dont have an answer to this. why would some people use one of the above options and not the other or vice versa.

THIS IS WHAT THE APPLE WEBSITE SAYS:
"Clock source:
Leave the “Clock source” pop-up menu set to Default unless you’re using an audio device that sends its own timing (clock) messages."

The "normal" setting in audio midi setup says clock source default. only when my dac is set as an aggregate device does the name of the dac appear next to clock source. this is what i want. to make sure the dacs clock is being used as it is an expensive dac used for audio hifi through beyer dt880 headphones. so it would be okay to set the dac as an aggregate device but i thought aggregate devices were for multiple devices. i only have one external device device connected to the imac ie my dac. also i am not an audio expert by any means. here is the same query from someonelse on the computer audiophile website:

"I just purchased a NuForce U Dac2 SE that is Asynchronous. You have to forgive me if this is a newbie question, but does the internal clock of the DAC automatically get utilized? The DAC itself is working fine but the screen in the Audio MIDI setup says the clock source is: default. The Help menu for clock source says:
"Leave the “Clock source” pop-up menu set to Default unless you’re using an audio device that sends its own timing (clock) messages."
The thing is I can't seem to find any pop up menu to select clock source, Again it just says "default" which leads me to believe the macs own clock is being used. I can choose the format and set it to 96khz. I include a screen shot if that helps. Any thoughts?"
it goes on: "Just trying to verify if it's own clock is being used when connected to a Mac since the Mac lists the clock as "default" and I don't know whether that means the DACs own clock or the Mac's."

i would be so grateful if the real experts here could dig deep and find the definitive 100% correct answer to this. after nearly a year i have been unable to. the dac i will be using costs in excess of £1300. 

many thanks to all.MK.
musickid

 

[Roseval]

It is a bit unclear what this OSX Clock source is supposed to do but I wonder if it really matters.
 
Asynchronous USB is USB in isochronous mode with asynchronous synchronization.
This means the clock of the DAC runs at its own pace.
The USB receiver watches the buffer.
If it drains to fast, it tells the PC to send more data, if it is filled to fast, it tells the PC the opposite.
This has nothing to do with clocking at the PC side (you can’t change the clocking of the USB bus) but with delivering the right amount of data at the right time.
Bit more detail: http://www.thewelltemperedcomputer.com/KB/USB.html