I have posted the data sheet, the above sims include the 75R resistor that I did suspect would be there as per the data sheet....
I dont agree with that statement, if you dont know what you are doing leave it alone, also if it works leave it alone... so in this case leave it alone you are more likely to make things worse (surprisingly digital tweaks often make things worse).
Still waiting why do you need performance down to a few Hz for a digital signal in the MHz.....
C0G/NP0 is better than even PPS film in most characteristics and PPS SMT/SMD film is hard to solder by hand with confidence that you have not damaged the cap. Especially by an amateur.
There will be no harm in using a larger value of NP0/C0G cap as the impedance at RF frequencies is mainly dictated by the package and mounted inductance.
Is it necessary to have good LF performance? Probably not but it won't hurt.
I don't buy into the cult of Jocko even though he does know what he is talking about. I simply do not think the SPDIF interface makes much if any difference with one of the modern receiver ICs such as the AKM or Wolfson. I would be very surprised to see any measurable difference at the analog output of a DAC (where it actually counts). I don't put much stock in the subjective impressions of anyone.
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The only digital signal that I know of, and accept as being a "digital signal" is a +24V signal (used as "high" for PLC digital input or output cards, to mention one example).
Everything else should be treated as analog. In fact S/PDIF signal has to be nurtured with much more care than 20Hz to 20kHz analog.
Same care applies to USB "digital" signal. I find statements about USB being nothing but "zeros and ones" very entertaining.
Nick
Everything else should be treated as analog. In fact S/PDIF signal has to be nurtured with much more care than 20Hz to 20kHz analog.
Same care applies to USB "digital" signal. I find statements about USB being nothing but "zeros and ones" very entertaining.
Nick
Usually SPDIF converters and stuff use 10/100nF. I saw lot more distortion in the signal when I switched from a (0.5m) factory cable to my home made 3m long cable (became worse).
So I don't think it will make too much difference if you use 10nF or 100nF or ceramic or other type. Lot more matters on the source, on the cable, on the implementation.
So I don't think it will make too much difference if you use 10nF or 100nF or ceramic or other type. Lot more matters on the source, on the cable, on the implementation.
The fact though that 0 and 1s are being transmitted makes it a digital signal so you treat it as such and if necessary use signal integrity tools to check on how the signal propagates from a to b. Below is the scenario I used for some SPDIF for above and some earlier discussions on SPDIF and analogue attributes....
The digital signals are far easier to transmit than analogue signals, and get the resultant data be it music or a meter reading from a to b intact and unadulterated, hence it ever increasing use as a data transport medium instead of analogue.. Digital signal transmission is well understood as are the methods of moving the signals around. This digital is analogue (meaning analogue like an audio signal, not the rf analogue attributes it really has) and bits aren't just bits is the wrong way to look at signal transmission and does seem very popular amongst some audiophiles... hence the earlier thread where the shape of the SPDIF signal was being viewed and compared to the resultant analogue output.
Firstly digital is generally high speed so the analogue harmonics of the signal follow the path of least inductance, whereas raw analogue music is low frequency and follows mainly the path of least resistance, so star grounding aint going to be a good idea for digital signals... just one example....
The digital signals are far easier to transmit than analogue signals, and get the resultant data be it music or a meter reading from a to b intact and unadulterated, hence it ever increasing use as a data transport medium instead of analogue.. Digital signal transmission is well understood as are the methods of moving the signals around. This digital is analogue (meaning analogue like an audio signal, not the rf analogue attributes it really has) and bits aren't just bits is the wrong way to look at signal transmission and does seem very popular amongst some audiophiles... hence the earlier thread where the shape of the SPDIF signal was being viewed and compared to the resultant analogue output.
Firstly digital is generally high speed so the analogue harmonics of the signal follow the path of least inductance, whereas raw analogue music is low frequency and follows mainly the path of least resistance, so star grounding aint going to be a good idea for digital signals... just one example....
Attachments
Apart from the specific instructions in the data sheet on how to implement the interface.....
If the 10nF value was critical the datasheet would probably say so. I suspect that basically all that is needed is a DC blocker with good performance in the MHz region. Anything from a few nF to a few 10s of nF would do. Smaller than that and you start to lose wanted lower frequencies. Bigger than that and you start to get poor RF performance.
They probably chose a ceramic because it has good RF performance, a bit of nonlinearity does not matter in a coupling cap of the correct value, and it will be small so pick up little interference and have only small stray capacitance to ground.
So a 10nF ceramic is probably the optimum choice, but as it is uncritical there is plenty of scope for audiophiles to 'improve' the circuit without doing too much damage to signal integrity. If a different cap makes it genuinely sound different then the different cap is probably wrong.
They probably chose a ceramic because it has good RF performance, a bit of nonlinearity does not matter in a coupling cap of the correct value, and it will be small so pick up little interference and have only small stray capacitance to ground.
So a 10nF ceramic is probably the optimum choice, but as it is uncritical there is plenty of scope for audiophiles to 'improve' the circuit without doing too much damage to signal integrity. If a different cap makes it genuinely sound different then the different cap is probably wrong.
You do tend to find that when there is a problem with a design and you phone up technical support one of the first things they ask is have you followed the data sheet (or example design) specifications.
To really tailor the sound though, why not take the SPDIF shield (and return) connection and fasten it to some remote star point🙂
To really tailor the sound though, why not take the SPDIF shield (and return) connection and fasten it to some remote star point🙂
For a brief moment I envisaged a galaxy far far away and wondered if some audiophile dealer was offering distant grounding points which could be accessed via his gold-plated wormhole ($15 000 each), then I realised that you were just referring to the other side of the chassis - just far enough away to damage the signal.marce said:
Hi, Nick,
Except, that binary signal transfer IS nothing but ones and zeroes. The whole point of digital information technology, from processing, to transfer, to storage is that it is resistant to the degradations that affect (alter) information handled in it's analog form. Digital is considered robust in it's relative insensitivity to noise and distortion as compared to analog. As long as a binary signal transfer can accurately be resolved at the receiving end in to the ones and zeroes that were transmitted it is perfect. While the physical handling of digital information is performed by physical devices having intrinsically analog properties, the information is digital with respect to how it is encoded and interpreted, which means the analog degradations of the physical devices are essentially irrelevant, inside certain limits.
A short link S/PDIF or USB interface can accurately transfer the ones and zeroes of a digital audio signal data between transport and DAC. Both clock and data can be accurately recovered by the DAC's input receiver. Yes, the clock as well, as it, too, is a binary signal. The only purpose of the clock in a digital signal transfer is to delineate the data. The reason why S/PDIF is a problematic interface for digital audio is because the transferred digital signal will eventually be converted to an analog signal. The timing of this conversion is largely determined by the phase stability (jitter) of the recovered clock. It's only here, at the moment of data domain conversion, that an digital system is subject to the degradations affecting analog systems. Even asynchronous USB can still be subject to jitter degradation of a DAC's locally generated clock signal due to ground noise coupling between the computer source and the DAC.
If not for the eventual conversion of the signal from digital to analog domains, S/PDIF or USB would essentially operate perfectly in performing the task of a short length, low rate digital clock and data transfer.
Well said, Ken.
I would add that S/PDIF, like most modern data transfer protocols, is phase encoded. Ones and zeros are represented by the number of state transitions in a bit period. As such, the shape of the signal, the slope of the edges, and the absolute timing are irrelevant.
I would add that S/PDIF, like most modern data transfer protocols, is phase encoded. Ones and zeros are represented by the number of state transitions in a bit period. As such, the shape of the signal, the slope of the edges, and the absolute timing are irrelevant.
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