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Digital Signal Transmission


TomJ

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15 hours ago, pkane2001 said:

 

A doctor subscribing to Frank's approach to diagnosing may not be my first choice :)

 

Me: Doctor, I've been having this cough....

Dr Frank: Let's remove your appendix, it's most often a problem in people of your age

Me: shouldn't we at least run some tests, get some lab results, an X-ray or two?

Dr Frank: No need, tests are for those other doctors that read textbooks and look at charts

Me, a week later: Doctor, my appendix was removed and yet I'm still coughing

Dr Frank: Ah, that's because you have two kidneys and they are unbalanced. We'll need to remove one.

Me, two weeks later: Doctor, I'm still recovering from the two surgeries, but my cough has not gone away

Dr Frank: It must be your heart, let's do a bypass

Me, a month later: Doctor, I'm feeling awful, I can barely move, have chest pain, and bleeding from all my incisions... but I'm still coughing

Dr Frank: I suspect it's your foot. We'll need to amputate

Me: I'd like to get a second opinion from one of those "other" doctors, if you don't mind

 

 

 

First time I've seen doing major surgery called, diagnosis - you may care to note that I always aim to do the bare minimum to the guts of whatever I deal with, to 'fix' it - with current actives, I have not even opened them up yet - no idea what it looks like inside. So, being radical in that sense is not part of the recipe, 😀.

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3 hours ago, asdf1000 said:

 

Rob Watts talks about RF all the time for years now on Head-Fi forum. He describes it like a "fungus" that gets to all parts of a DAC. Increases IM distortion 

 

"Fungus" is a good term to use - the sense of relief when all 'fungus' is extinguished is, umm, palpable 😀 ... many people never reach this point, so don't understand what the fuss is all about ...

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I mean I have my Ph.D. in Mycology :D

Current:  Daphile on an AMD A10-9500 with 16 GB RAM

DAC - TEAC UD-501 DAC 

Pre-amp - Rotel RC-1590

Amplification - Benchmark AHB2 amplifier

Speakers - Revel M126Be with 2 REL 7/ti subwoofers

Cables - Tara Labs RSC Reference and Blue Jean Cable Balanced Interconnects

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1 hour ago, fas42 said:

 

First time I've seen doing major surgery called, diagnosis - you may care to note that I always aim to do the bare minimum to the guts of whatever I deal with, to 'fix' it - with current actives, I have not even opened them up yet - no idea what it looks like inside. So, being radical in that sense is not part of the recipe, 😀.


I think surgery often follows a radical diagnosis, such as excising a volume control, but I’m not a doctor ;)

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4 hours ago, pkane2001 said:


I think surgery often follows a radical diagnosis, such as excising a volume control, but I’m not a doctor ;)

 

If one is very careful not to hear differences, when some experiment is made, to test whether some factor may relevant - because to do so threatens one's carefully built up set of ideas - then most things are probably radical. If one does not suffer this affliction, then that person can determine that indeed the volume control is a weakness - then, either grin and bear it; or, do something to improve matters ... which might be to remove that part from the circuit.

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So I sum up:

  • Data is not changed on its long way across networks. The correct data always arrives at the network end point (e.g. network streamer)
  • Jitter problems in switches do not cause "worse" data, but produce "noise".
  • "Noise" can "jump" from one side to the other in a device even though there is electrical isolation.
  • Although Ethernet is always galvanically isolated on the data path (if shielding is not used), "noise" is transmitted from the previous one.
  • In order to transfer the data from the network endpoint to the DAC, USB is superior to the other transport options.
  • Jitter can worsen the sound in the DAC when converting from digital to analog. These can be caused by "noise" entering the DAC via electrical channels or by EMI in the environment.
  • Sound improvements or deteriorations through "noise" via the digital transmission path cannot (or only with great difficulty) be measured.
  • A USB isolator does not eliminate all of the "noise", but perhaps only 60%.
  • The aim must be to keep "noise" out of the DAC.

 

If noise is the cause of all the evil and the effect cannot be measured, why is the cause not simply measured ("Noise")?

Why not stated the noise level for products done by measurements , but always only talked about sound-enhancing "Low Noise" products without giving any values?

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Another Point:

 

  • If the network "end-point" have to much work to correct false data (TCP/IP), it produce more noise by calculation. (Have there been any measurement about corrupt packages at network endpoints (e.g. streamer) yet?  This would increase the reputation of so called audiophile switches, but "you can hear it - no need for measurements"😁)

 

So there are things you can measure regarding sound quality:

  • Measurement of noise level entering the DAC or of the ethernet path.
  • Date integrity of the network transport. (should be easy, because this is daily business of IT guys). If a super-duper clock in a switch will be worth, then an improvement should be measured.

 

Why cant I see discussions based on those facts and only read about magic stuff is going on?

 

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2 hours ago, TomJ said:

If noise is the cause of all the evil and the effect cannot be measured, why is the cause not simply measured ("Noise")?

Why not stated the noise level for products done by measurements , but always only talked about sound-enhancing "Low Noise" products without giving any values?

 

Because it is hard to give meaningful measurements - its effects could be measured, but no-one has clear ideas on what precisely to measure. On the cause side, it would be possible to make all sorts of measurements of various types of noise; but actually pinning any of these measurements on what is subjectively heard would be difficult - one could wave one's hands and say that the lowest numbers are probably going to mean the best performing device; but this would just be guessing.

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1 hour ago, fas42 said:

 

Because it is hard to give meaningful measurements - its effects could be measured, but no-one has clear ideas on what precisely to measure. On the cause side, it would be possible to make all sorts of measurements of various types of noise; but actually pinning any of these measurements on what is subjectively heard would be difficult - one could wave one's hands and say that the lowest numbers are probably going to mean the best performing device; but this would just be guessing.

 

I thought the effects could not be measured, only heard?

 

But when a company begins to develop a device, it has to define the goals - if that's just "improving sound quality" and you're just messing around with the try and error method, then I can understand the high prices, but also the professionalism and traceability is doubted and people like Amir are most welcome.

 

For example, for a network switch (sorry to overemphasize this topic) at least two things must be achieved:
- Noise reduction - could be measured
- Data integrity - could be measured

Maybe there are a few other things that I am missing, but at least these two points are widely accepted.

 

For example, I don't think an audiophile switch has any higher data integrity. However, this would be very easy to prove with a simple measurement by the manufacturer. But maybe one is afraid that this is not the case.

 

I also doubt, for example, that the noise level will be lowered that much compared to a standard switch with LPS. That would be easy to prove. But I always only get the answer, I have to believe it and trust my ears.

If the producer could prove something here, they would have more customers. Do they not want this?

 

 

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14 hours ago, botrytis said:

 

Nothing wrong with fungus - I hate when people disparage fungi.

 

If you like Miso, soy sauce, blue cheese, and any alcohol thank your local fungi.....

 

Love mushrooms of all kinds!

 

Oh, and also Star Trek Discovery. You'll know why if you've watched it -- fungi run the universe.

 

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33 minutes ago, PeterSt said:

Now Paul, come on. You say that all these things can easily be measured. Now teach me how (but bring some money please, if required).

;-)

 

As you know, I really don't care what happens in the middle of a DAC or before it. These are irrelevant to me, as I don't listen to the 22MHz clock or to USB packets or to TCP/IP frames. I listen to analog output of a DAC. Regardless of the original source of distortions, be it jitter, noise, RFI, EMI, cheap fuse or power cord, etc., if I can't detect it at the output below, say 24KHz, I don't really care if it's there (and for me, personally, under 18KHz is plenty good enough.)

 

And yes, below 24KHz, I can measure pretty well without the need for $150K in equipment 😜

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1 hour ago, pkane2001 said:

 

As you know, I really don't care what happens in the middle of a DAC or before it. These are irrelevant to me, as I don't listen to the 22MHz clock or to USB packets or to TCP/IP frames. I listen to analog output of a DAC. Regardless of the original source of distortions, be it jitter, noise, RFI, EMI, cheap fuse or power cord, etc., if I can't detect it at the output below, say 24KHz, I don't really care if it's there (and for me, personally, under 18KHz is plenty good enough.)

 

And yes, below 24KHz, I can measure pretty well without the need for $150K in equipment 😜

 

Just be careful that your measurement gear's anti-alias filter doesn't fix up things that that DAC didn't do properly... ;)

 

If you run a NOS DAC at 44.1k sampling rate and put it through nice oversampled 20 kHz brickwall filter in analyzer, the resulting waveforms may look pretty decent. But it is not what is coming out of the DAC. :D

 

Let's say Focusrite Forte interface. Playing 0 - 22.05 kHz sweep with spectrum "peak hold" looks like this:

Forte-sweep-wide.thumb.png.93b3193d68336545f23f936d7b4a680e.png

 

And 1 kHz tone looks like this in wide band:

Forte-1k-wide.thumb.png.c52cc456396f4a3c6f3fadc7039bcbbb.png

 

I'd say that device puts out lot of correlated junk. If you run that to a class-D amp like Hypex you may have some funny side effects.

 

 

Signalyst - Developer of HQPlayer

Pulse & Fidelity - Software Defined Amplifiers

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11 minutes ago, Miska said:

 

Just be careful that your measurement gear's anti-alias filter doesn't fix up things that that DAC didn't do properly... ;)

 

If you run a NOS DAC at 44.1k sampling rate and put it through nice oversampled 20 kHz brickwall filter in analyzer, the resulting waveforms may look pretty decent. But it is not what is coming out of the DAC. :D

 

Let's say Focusrite Forte interface. Playing 0 - 22.05 kHz sweep with spectrum "peak hold" looks like this:

Forte-sweep-wide.thumb.png.93b3193d68336545f23f936d7b4a680e.png

 

And 1 kHz tone looks like this in wide band:

Forte-1k-wide.thumb.png.c52cc456396f4a3c6f3fadc7039bcbbb.png

 

I'd say that device puts out lot of correlated junk. If you run that to a class-D amp like Hypex you may have some funny side effects.

 

 

 

I usually set the ADC at 96KHz to avoid this type of collision of filters.

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17 minutes ago, semente said:


Wouldn’t life be a lot easier if we weren’t able to measure a lot of stuff? And cheaper?

 

Why complicate when there’s a simplistic measure for DAC performance called SINAD which tells us all we need to know (that all DACs sound the same)? With pink panther ratings.

 

SINAD does work really well for saving $$$'s (and sanity, to some degree), even if it's not entirely accurate ;)

 

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1 minute ago, Miska said:

That is still not sufficient. I rather set ADC to 10 MHz... And then I still verify it with 200 MHz ADC (but with loss in dynamic range).

 

No need to do that to detect the effects of jitter in digital transmission or the DAC clock -- these either are there and can be measured in the audible range, or they are irrelevant.

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