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Digital Signal Transmission


TomJ

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6 hours ago, TomJ said:

With the isolator between my streamer and the RME ADI 2 DAC, this effect is over. Everything that is done in front of the isolator no longer has any (audible) influence on the sound.

 

Well it has, if you for example switch the ADI-2 to DSD Direct mode and always run it at DSD256. Instead of let's say sending 44.1k PCM there. Or alternatively running it at 705.6/768k 32-bit, which bypasses and improves over it's built-in digital filters which run only up to 352.8/384k.

 

And then you have wide variety possible digital filters and modulators you could run.

 

And this is all "in front of isolator"...

 

Signalyst - Developer of HQPlayer

Pulse & Fidelity - Software Defined Amplifiers

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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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  • 2 weeks later...
9 hours ago, John Dyson said:

The real problem is that some measurements that the subjective can detect do not have an objective measure (or an easy objective measure) yet.   Example is TIM back in the 1970's.   Some things are really hard to measure.   I deal with such things all of the time.

 

And TIM seems to have been forgotten again. However, I've taken it back to my measurement suite I use for my testing purposes.

 

One reason may be digital systems where it is not possible to directly measure (using the original test signals) with sampling rates below 192k. But now most DACs can do 384k and many 768k. And DACs can also do DSD which allows this type of measurement much better.

 

Signalyst - Developer of HQPlayer

Pulse & Fidelity - Software Defined Amplifiers

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