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plissken

Would forum members chip in $$ for a USB analyzer

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12 minutes ago, Teresa said:

I agree with Speed Racer perhaps new DACs should move away from USB. Maybe something like Thunderbolt.

 

Does Thunderbolt have the same issue as USB? I don't know and I need to get educated on that.

 

I still think an Ethernet to AES/EBU or S/PDIF coax connection is the way to go based on what we have today. That can be an Ethernet to AES/EBU DDC or a low noise audio streamer/end point on Ethernet outputting AES/EBU or S/PDIF coax.

 

This eliminates the sinkhole that is USB....

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mansr   
3 hours ago, Miska said:

Ethernet? ;)

Ethernet using what protocol? Unless you're using a dedicated link, you need to deal with address assignment, device discovery, etc before you can even think about sending audio data. But you obviously know all that.

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Jud   
12 hours ago, jabbr said:

Instead of a protocol analyzer I'd invest in:

 

1: (generally) a good high speed oscilloscope (can do eye patterns)

2: high resolution spectrum analyzer

3: vector signal analyzer

 

Re number 2, was poking around and ran across this: http://www.specs-zurich.com/en/high-resolution-oscilloscope-and-spectrum-analyzer-_content---1--1548--259.html

 

I noticed it features a "1 MS/s sampling rate."  So how, if at all, does it affect measurements we want to do if the measuring device is sampling at a lower rate than some of the clock rates we're dealing with?  Use this tool only for measurements where that isn't a factor, I assume?  (I'm supposing the answer to that may well be "Yes, fool."  ;) )

 

So what sorts of audio system measurements would number 2 and number 3 be useful for?

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jabbr   
56 minutes ago, mansr said:

Ethernet using what protocol? Unless you're using a dedicated link, you need to deal with address assignment, device discovery, etc before you can even think about sending audio data. But you obviously know all that.

 

The Ethernet->I2S/DSD interfaces will generally run ARM perhaps with an associated FPGA (e.g. Zynq), but not necessarily (e.g. rPi). Or another SoC such as ClearFog (Armada). Lots of options. Each DAC needs an ALSA driver. A remote network protocol such as netJACK->ALSA or @Miskas NAA would connect. The interface would run some version of Linux, typically. Presumably one could do the same type of thing for Windows IoT.

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plissken   
1 hour ago, mansr said:

Ethernet using what protocol? Unless you're using a dedicated link, you need to deal with address assignment, device discovery, etc before you can even think about sending audio data. But you obviously know all that.

Vendors can solve that by just not being typical developers in that regard:

 

1. Statically assign a default IP Address. Sonic Wall and others do this with their firewalls. Use something like 172.16.100.254/24

 

2. Have a simple web server for management of the IP stack built in. If you can get this in a $100 Printer/Copier/Fax you can get this in a $500/$1000/$5000 DAC.

 

Post a 5 minute video on how to configure your computer.

 

I have to take Auralic to task for a hands down stupid implementation.

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kilroy   
13 hours ago, Speed Racer said:

Why would we want to invest in this? If we were smart, we would be looking for ways to get away from USB. That's the future anyway. 

 

Explain how it's the future. What's around the corner we'll all be using in a year or three.

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mansr   
7 minutes ago, Jud said:

Re number 2, was poking around and ran across this: http://www.specs-zurich.com/en/high-resolution-oscilloscope-and-spectrum-analyzer-_content---1--1548--259.html

 

I noticed it features a "1 MS/s sampling rate."  So how, if at all, does it affect measurements we want to do if the measuring device is sampling at a lower rate than some of the clock rates we're dealing with?  Use this tool only for measurements where that isn't a factor, I assume?  (I'm supposing the answer to that may well be "Yes, fool."  ;) )

It also has only 18-bit resolution and 100 kHz analogue bandwidth. This is just barely enough for audio signals. If you want to measure digital signals, look elsewhere. For analogue audio purposes, you might as well use a $500 recording interface such as those from Focusrite, RME, and Tascam.

7 minutes ago, Jud said:

So what sorts of audio system measurements would number 2 and number 3 be useful for?

I don't know what you'd use a vector signal analyser for here. Those are typically used to study complex modulations in RF signals.

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10 hours ago, Speed Racer said:

 

Does Thunderbolt have the same issue as USB? I don't know and I need to get educated on that.

 

I still think an Ethernet to AES/EBU or S/PDIF coax connection is the way to go based on what we have today. That can be an Ethernet to AES/EBU DDC or a low noise audio streamer/end point on Ethernet outputting AES/EBU or S/PDIF coax.

 

This eliminates the sinkhole that is USB....

 

The DAC designers I've talked to about Thunderbolt all say it's a terrible interface compared to USB because it's so high speed that the noise is off the charts. 

 

 

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jabbr   
39 minutes ago, Jud said:

So what sorts of audio system measurements would number 2 and number 3 be useful for?

Regarding 1,2 and 3 (scope , spectrum analyzer. vector analyzer) there is overlap among the 3 and each tool is used for different applications or may have specs that are tuned for a specific measurement.

 

(short answer : lots of stuff)

 

a high resolution scope can do eye-patterns for example. Maybe you'd do 4 gsps for 1-2 Ghz resolution but at 8 - 12 bits. : realtime info

 

spectrum analyzer: FFT plots so my old HP 3561a 125 microHz to 100 kHz at 640 micro Gz intervals -- thus also forms part if a really really close in phase noise measurement (using a really good phase comparitor) -- generally great for looking at harmonics : non realtime info

 

vector analyzer: eg HP 89441a -- all in one phase noise much faster & quicker & easier

 

newer packages are digital & have special software modules to automate measurements -- this is less than scratching the surface :) 

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mav52   
39 minutes ago, AJ Soundfield said:

Crazy talk, but I agree. ;)

 

Should funding include cost of an audiophile power cord for the analyzer, else the results lack resolution and revealingness?

Crazy talk , yep

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jabbr   
59 minutes ago, The Computer Audiophile said:

 

The DAC designers I've talked to about Thunderbolt all say it's a terrible interface compared to USB because it's so high speed that the noise is off the charts. 

 

 

That and other reasons ! 

 

Not widely integrated into motherboards so forget about SoCs (cpus with integrated I/O etc)

 

No reason to think it would be better than Ethernet

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6 minutes ago, Wavelength said:

Full Speed sure is ceiling is pretty low at 32/96 being the max stereo sample rate. High Speed sure is limited to sixteen channels @ 32/192.

Could you define "low" and "limited" in terms of audio? Most "high end" audio rigs are 2ch.

 

Just think of what would happen if you guys did testing and the results were XYZ. Do you think that this would be argued over and over again and really what would that accomplish? Probably nothing...

Unless the point is arguing? :)

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jabbr   

@Wavelength -- hey neighbor !

 

< 10 Hz phase error -- yep hence HP 3048a ... need to resurrect a 486 slow enough to run the software !!

 

Zynq can do Ethernet and I2S both in FPGA side and logic/drivers in ARM side -- so equal facility with USB and SGMii (SFP -> fiber) ... better phase error than eg Marvel Armada

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1 hour ago, jabbr said:

Regarding 1,2 and 3 (scope , spectrum analyzer. vector analyzer) there is overlap among the 3 and each tool is used for different applications or may have specs that are tuned for a specific measurement.

 

(short answer : lots of stuff)

 

a high resolution scope can do eye-patterns for example. Maybe you'd do 4 gsps for 1-2 Ghz resolution but at 8 - 12 bits. : realtime info

 

spectrum analyzer: FFT plots so my old HP 3561a 125 microHz to 100 kHz at 640 micro Gz intervals -- thus also forms part if a really really close in phase noise measurement (using a really good phase comparitor) -- generally great for looking at harmonics : non realtime info

 

vector analyzer: eg HP 89441a -- all in one phase noise much faster & quicker & easier

 

newer packages are digital & have special software modules to automate measurements -- this is less than scratching the surface :) 

 

I have a mint 3561A yea with the bubble memory. It's a great piece for testing low noise analog stuff. I also have a Stanford SR760 which is a little better. The problem is getting the phase noise into these.

 

I have a Symmetricom phase noise analyzer that we use for testing crystals and oscillators. It's got a custom downloadable FPGA in it and a 10MHZ super low phase noise reference in it. We get good plots to 1Hz with this. Before we had that it was kind of hit and miss using a boat load of reference stuff.

 

Thanks,
Gordon

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9 minutes ago, Wavelength said:

As I said low in terms of sample rate. Full Speed is limited to 32/96 stereo or 2ch. 

I see. So a 48kHz playback upper end is "low" for 2ch audiophiles, many 60-70+.

Fascinating. I may have to rethink my supertweeter designs ;)

Thanks Gordon

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crenca   
2 hours ago, AJ Soundfield said:

Crazy talk, but I agree. ;)

 

Should funding include cost of an audiophile power cord for the analyzer, else the results lack resolution and revealingness?

 

 

Bah!!  

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jabbr   
2 hours ago, Wavelength said:

I have a mint 3561A yea with the bubble memory. It's a great piece for testing low noise analog stuff. I also have a Stanford SR760 which is a little better. The problem is getting the phase noise into these.

The HP 11848a is the phase noise interface but no doubt a modern FPGA based device is vastly easier to use. 

 

The Stanfords are just a little bit too pricey for me . I scavenge for stuff being given away ;) 

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jabbr   
2 hours ago, Wavelength said:

Doing Ethernet in an FPGA is not something I would try. I bet if they are using an ARM processor on the board the Ethernet is probably going there.

 

Actually off the shelf nowadays. You can hang a SFP cage on the 3.3v IO lines and run the low level logic in the PL and send the packets to the ARM for the TCP/IP stack. The same clock domain crossing logic is used to send the bits back to the PL for output as DSD and PCM.

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Ralf11   
23 hours ago, wgscott said:

If the product isn't all smoke and mirrors, they would have a 30 day return policy emblazoned on their web page.  ;-)

 

I am tempted to 'love' this post too, as I agree with the general direction of the comment, but this is test gear.  How often can you return test gear?  That is more common for consumer items.  I've never seen a mass spectrometer that could be returned for example.

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