Is digital variable...?
Discussion
Apologies for the crap title, but I couldn't think of anything better at the moment.
A few things.
1. I have often wondered that provided a DAC has adequate jitter correction, does it matter at all what your source is...?
Let's say you play the same audio track from two digital devices via the same media (let's say SPDIF coax for sake of argument) into the same DAC, amp and speakers. The first source is a £5 MP3 player with a digitally ripped uncompressed WAV at 44.1kHz 16bit 2ch. The second is five-figures worth of CD transport playing the track from CD that the above WAV was derived from.
Again, assuming adequate jitter correction in the DAC, surely they will sound identical because (aside from jitter) what is being pumped into the DAC is effectively identical...?
Another way to look at it is if I make two digital copies of a CD track using SPDIF coax. Same recording device with a decent DAC that can correct jitter appropriately but for one CD I use a £15 ASDA CD player and for the other I use the 5 figure's worth mentioned above. If reviews are to be believed, the second copy should sound better when played back in a quality transport, but I can see knack all reason why.
2. Are digital cables snake oil...? My £50 Chord ProDAC Pro digital sounds no better than a coax I have that cost 19p. Assuming the connection is sound and there's not so much RF noise to completely knacker the signal, what's the benefit...? Same goes for HDMI stuff. Assuming again that the connections are good and ambient RF noise is not hideous, WTF is the difference between a £1 cable and a £50 cable. I have both (fortunately the latter was FOC) and can't tell sod all difference. I can appreciate that with an analogue signal, preservation of the signal and best mitigation of external RF is important, but with a digital signal, surely not...?
3. One of my CD players has a 1-bit DAC. The other has dual 16bit DACs with 8x oversampling. What's the difference...?
A few things.
1. I have often wondered that provided a DAC has adequate jitter correction, does it matter at all what your source is...?
Let's say you play the same audio track from two digital devices via the same media (let's say SPDIF coax for sake of argument) into the same DAC, amp and speakers. The first source is a £5 MP3 player with a digitally ripped uncompressed WAV at 44.1kHz 16bit 2ch. The second is five-figures worth of CD transport playing the track from CD that the above WAV was derived from.
Again, assuming adequate jitter correction in the DAC, surely they will sound identical because (aside from jitter) what is being pumped into the DAC is effectively identical...?
Another way to look at it is if I make two digital copies of a CD track using SPDIF coax. Same recording device with a decent DAC that can correct jitter appropriately but for one CD I use a £15 ASDA CD player and for the other I use the 5 figure's worth mentioned above. If reviews are to be believed, the second copy should sound better when played back in a quality transport, but I can see knack all reason why.
2. Are digital cables snake oil...? My £50 Chord ProDAC Pro digital sounds no better than a coax I have that cost 19p. Assuming the connection is sound and there's not so much RF noise to completely knacker the signal, what's the benefit...? Same goes for HDMI stuff. Assuming again that the connections are good and ambient RF noise is not hideous, WTF is the difference between a £1 cable and a £50 cable. I have both (fortunately the latter was FOC) and can't tell sod all difference. I can appreciate that with an analogue signal, preservation of the signal and best mitigation of external RF is important, but with a digital signal, surely not...?
3. One of my CD players has a 1-bit DAC. The other has dual 16bit DACs with 8x oversampling. What's the difference...?
Lots of questions. I'll answer some.
When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
JustinP1 said:
Lots of questions. I'll answer some.
When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
Cool, that answers a good chunk of the question thanks When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
Roop said:
JustinP1 said:
Lots of questions. I'll answer some.
When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
Cool, that answers a good chunk of the question thanks When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
scott.s said:
Roop said:
JustinP1 said:
Lots of questions. I'll answer some.
When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
Cool, that answers a good chunk of the question thanks When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
scott.s said:
Roop said:
JustinP1 said:
Lots of questions. I'll answer some.
When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
Cool, that answers a good chunk of the question thanks When you are playing back a digital signal you want it to be as accurate as possible in both quality and timing.
When you are running that data in real time off a spinning disc you have inherent problems in both of those. Obviously this is why a £5000 CD transport is better than £50 one.
Unfortunately in 1984 with 48k home computers they did not forsee that in 20 years time there will be home computers that could hold several million times more data and make exporting data to a DAC from a plastic disc obsolete.
To cut a long story short, I have just mothballed a £3000 transport in favour of a Mac Mini. They do the same job, but the Mac Mini produces a digital signal of exactly the same quality, if not better than my previous investment and is a hell of a lot more convenient.
A scientific or technical appraisal might be in order if you are just going to say someone is talking rubbish?
Roop said:
k
And solid state moreso again...
So you think it goes harddisk -> optical out? There might be a few more things in the path than that Mr_Yogi said:
scott.s said:
only that's just not true...............
A hard disk is so much more accurate than an optical based media such as CD, DVD, etc. 
ThatPhilBrettGuy said:
Roop said:
k
And solid state moreso again...
So you think it goes harddisk -> optical out? There might be a few more things in the path than that Mr_Yogi said:
scott.s said:
only that's just not true...............
A hard disk is so much more accurate than an optical based media such as CD, DVD, etc. ETFT
Edited by Roop on Wednesday 18th February 12:44
Roop said:
The mechanisms that convert what is effectively a datastream from the source (output from the CD transport data bus / hard disk data bus / solid state memory data bus into SPDIF via coax / TOSLink etc are comparable.
They're not. Massively not. I've looked at the microcode for the onboard controllers for some of that stuff and it's nothing like generic PC/Mac coding. All the timing is guaranteed and you don't get the O/S rescheduling your task for a bit because it wants to do some online update etc etc.I'm not saying playing data from a general purpose machine is bad, they're just not comparable dataflow wise.
ThatPhilBrettGuy said:
Roop said:
The mechanisms that convert what is effectively a datastream from the source (output from the CD transport data bus / hard disk data bus / solid state memory data bus into SPDIF via coax / TOSLink etc are comparable.
They're not. Massively not. I've looked at the microcode for the onboard controllers for some of that stuff and it's nothing like generic PC/Mac coding. All the timing is guaranteed and you don't get the O/S rescheduling your task for a bit because it wants to do some online update etc etc.I'm not saying playing data from a general purpose machine is bad, they're just not comparable dataflow wise.
Roop said:
ThatPhilBrettGuy said:
Roop said:
The mechanisms that convert what is effectively a datastream from the source (output from the CD transport data bus / hard disk data bus / solid state memory data bus into SPDIF via coax / TOSLink etc are comparable.
They're not. Massively not. I've looked at the microcode for the onboard controllers for some of that stuff and it's nothing like generic PC/Mac coding. All the timing is guaranteed and you don't get the O/S rescheduling your task for a bit because it wants to do some online update etc etc.I'm not saying playing data from a general purpose machine is bad, they're just not comparable dataflow wise.
ThatPhilBrettGuy said:
Roop said:
ThatPhilBrettGuy said:
Roop said:
The mechanisms that convert what is effectively a datastream from the source (output from the CD transport data bus / hard disk data bus / solid state memory data bus into SPDIF via coax / TOSLink etc are comparable.
They're not. Massively not. I've looked at the microcode for the onboard controllers for some of that stuff and it's nothing like generic PC/Mac coding. All the timing is guaranteed and you don't get the O/S rescheduling your task for a bit because it wants to do some online update etc etc.I'm not saying playing data from a general purpose machine is bad, they're just not comparable dataflow wise.
Generally a more Stable transport produces fewer read error's so Disc's can be read quicker and with less "error correction".
The Cable is spec'ed at 75 Ohm so a well put together "home" made cable should be quite good. The extra money usually goes on better shielding from RF and Plugs that do not oxidise degrading the signal.
Jitter is essentially a "timing" problem. Very Simply put The signal should be received as a series of pulses. These pulses are expected at set intervals. When the interval is not what was expected "Jitter" occurs and the pulse has to corrected or resent. Where the Transport and DAC are seperate items two things can be done to correct this. The first is that the "clock" that sets the pulses can be controlled by the DAC. The Second is to "buffer" the input and "reclock" the pulses.
As for the differences between 1-bit and 16 bit Dacs you are going into dangerous territory. The Theory is that a 16 or 24 bit converter takes the Whole 16/24 bits in and converts it as is. A 1 bit converter "loops" round to construct the analogue signal from a 16 bit signal one bit at a time. This actually gives it "20 bit" resolution from a 16 bit signal. When you look at the signal the pulses constructed are very widely spaced. The signal produced is very smooth because it seems to average out the distance between the pulses to produce the analogue wave.
The Cable is spec'ed at 75 Ohm so a well put together "home" made cable should be quite good. The extra money usually goes on better shielding from RF and Plugs that do not oxidise degrading the signal.
Jitter is essentially a "timing" problem. Very Simply put The signal should be received as a series of pulses. These pulses are expected at set intervals. When the interval is not what was expected "Jitter" occurs and the pulse has to corrected or resent. Where the Transport and DAC are seperate items two things can be done to correct this. The first is that the "clock" that sets the pulses can be controlled by the DAC. The Second is to "buffer" the input and "reclock" the pulses.
As for the differences between 1-bit and 16 bit Dacs you are going into dangerous territory. The Theory is that a 16 or 24 bit converter takes the Whole 16/24 bits in and converts it as is. A 1 bit converter "loops" round to construct the analogue signal from a 16 bit signal one bit at a time. This actually gives it "20 bit" resolution from a 16 bit signal. When you look at the signal the pulses constructed are very widely spaced. The signal produced is very smooth because it seems to average out the distance between the pulses to produce the analogue wave.
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