We need a new standard in transferring digital signals between audio equipment.

[jabbr]

On 2/25/2024 at 4:02 PM, Jud said:

 

If needed/wanted, it's available. Because there's no copper connection, there's power injection at the DAC end, and I think quality of the power supply matters there.

 

https://fibbrcable.com/products/alpha-usb-a-b-optical-fiber-digital-audio-cable

Everything in the DAC and after the DAC matters. That's the only place we should really need bespoke hardware. Every thing else in audio can be done with software and commercial hardware.

[Jud]

34 minutes ago, jabbr said:

Everything in the DAC and after the DAC matters. That's the only place we should really need bespoke hardware. Every thing else in audio can be done with software and commercial hardware.

 

Which is why you have a balanced transformer supplying power and optical cables in the signal path?

 

The power injection goes through the output of the cable to my DAC's USB port and will run it if the DAC's own power supply is removed. So as long as that power is connected to the DAC it may as well be decent quality, subject as little as possible to ground/noise currents.

[John Dyson]

5 hours ago, jabbr said:

Everything in the DAC and after the DAC matters. That's the only place we should really need bespoke hardware. Every thing else in audio can be done with software and commercial hardware.

You have it (I agree!!!) -- except for network dropouts and underruns/overruns, the digital networks are transparent.   There is always the possibility of some influence from digital leaking into analog, but that is always circuitry associated with the DAC.    This digital noise leaking into the analog signal processing and amplifiers is miniscule given competent circuitry and layout.   It is this 'leakage' where noise in the digital timing (clock instability) might be influenced, of course, that would also include noise in the clock itself.  (A major source for clock noise would be the 1/f effects of semiconductor type devices -- the higher the freq, the more likely there will be 1/f noise in the semiconductor oscillator...   There ARE some bias feedback schemes that can and do help.)   Board layout and circuitry isolation of the direct clock associated with the DAC and analog associated with the DAC directly are areas where the consumer might find improvement by better selection of constituent devices.

 

When mentioning that digital networks are transparent, that assumes that there is no digital transcoding for transmission efficiency.   For example, if a 'flac' or raw digital signal 'normal PCM wav' is sent raw, then then digital transmission under non-stress conditions will produce a perfect image on the other side.   If there is an 'lossy efficiency enhancement' like something similar to mp3 coding during transmission, then of course there will be profound signal qualiity loss (relative to raw digital).    Perhaps a common usage of 'efficiency improvement' might be the real-time Dropbox player.

 

Local ethernet connections are an extension of internet type communications, and the very timing 'insane' transmission of the internet is often utilized for 'perfect' transmission of raw digital data.   If worried about quality, the most important matters are at the ends of the digital transmission scheme (including signal source quality and DAC/analog interface.)   The signal source qualitiy matters (off topic) also include the consumer materials as distributed.

 

This situation isn't really all that complex.   No matter what, once in a while we all self-misdirect when problem-solving.

 

John

 

[jabbr]

7 hours ago, Jud said:

 

Which is why you have a balanced transformer supplying power and optical cables in the signal path?

 

The power injection goes through the output of the cable to my DAC's USB port and will run it if the DAC's own power supply is removed. So as long as that power is connected to the DAC it may as well be decent quality, subject as little as possible to ground/noise currents.

 

Sure, I mean first of all not all commercially available standard networking equipment is the same, nor all servers but that said the modern networking equipment has been designed to work with standard power supplies that plug into the wall. Fairly extraordinary noise elimination that happens on the boards and within the chips themselves.  Extraordinary as in check out the eye pattern of a 200Gbe lane. 

 

Yes the DAC needs to be designed in the same way that all modern networking equipment is designed. It needs to lock onto an async clock domain and smooth out an imperfect input signal. This is done in every modern ethernet device. The DAC needs to be designed to either accept a specified clean external power source or clean up its own AC signal. But yes the DAC is an audio device and should be in a clean power environment. The DAC also needs to deal with filtering out high frequency digital signals/noise e.g. DSD ... that's how it works!

 

The concept that noise flows down an Ethernet chain comes from the past centrury and was dealt with in the 1990s. Just use modern equipmemt which is explicitly designed to prevent that. I'm not talking about $5 ethernet switches with $3 power supplies.

[jabbr]

2 hours ago, John Dyson said:

You have it (I agree!!!) -- except for network dropouts and underruns/overruns, the digital networks are transparent.   There is always the possibility of some influence from digital leaking into analog, but that is always circuitry associated with the DAC.  

Exactly and solved by enough bandwidth as well as protocol selection. Ravenna is almost the sole example of audio specific network hardware but come to think of it the very modern NICs e.g. NVidia/Mellanox and AMD/Xilinx are themselves programmable and Ravenna could be programmed onto these NICs if there were sufficient interest ... Ravenna is at the firmware level ... the trend is that what was hardware a few years ago becomes software/firmware today. I will say that using Ravenna in a concert hall with multiple distributed amps/speakers almost proves my statement that everything can be done with standard network equipment and specialized drivers/software. I do think that increasingly multichannel arrays of speakers with convolutions of spatial filtering as well as equipment corrections will be the future (mostly software).

 

In the same way that post 1999 design ethernet receivers must handle imperfect inputs without increasing noise, DACs need to handle slightly imperfect inputs. 

[jabbr]

8 hours ago, Jud said:

The power injection goes through the output of the cable to my DAC's USB port and will run it if the DAC's own power supply is removed. So as long as that power is connected to the DAC it may as well be decent quality, subject as little as possible to ground/noise currents.

 

Also let me reinforce that the DAC and anything directly connected to it either input or power supply is fair game as part of the audio specific system! 

 

My point however is that there are established ways to essentially 100% block noise transmission i.e. fiber cables, modern reclocking chips, clean power, good design. With proper design the idea that upstream noise from the disk drives of a NAS somehow makes its way into the DAC is complete fiction

[Jud]

I think (as always, for everything that any of us says) things are never quite so neat as to be encapsulated in a few sentences in the space of a comment on a website. Software can take care of processes that would otherwise be in the DAC (for example, oversampling and sigma-delta modulation) as well as outside it. And I've had the experience, with modern well built equipment, of having copper Ethernet be part of a quite audible noise loop. So much as we might like, there doesn't seem to me to be a firm dividing line between the DAC and the rest of the system. We do what we can, which luckily with today's commercially available equipment is quite a lot without extraordinary expense. There is of course always something else one can do. Even with optical Ethernet and optical USB, one can try to minimize any possible noise from opto-electronic conversion.

 

Whether such measures have audible impact, I can't personally say with any certainty. I just try to do what seems sensible to me within my budget, and pay attention to measurements and discussions by folks who are more knowledgeable.

[jabbr]

Oh believe me I started down this rabbit hole chasing ground loops! at least 99.9% of the benefit of fiber is the absence of ground loops ... but yeah fiberoptic is standard tool in the modern networking armamentarium.  Its not that there isn't noise in opto-electronic conversion, its that noise from the rest of the system doesn't pass over a modern fiberoptic network. If you wish, the firm dividing line where upstream noise ends is where the glass fiber ends. That's essentially the end of the network and apropos this topic, we need if anything better DAC isolation, or signal filtering, or corrections in the digital domain, or multichannel synthesis etc. these are the areas where advanced in our hallucination of "being there" will occur.