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QuantAsylum QA400 and QA401
QuantAsylum QA400 and QA401
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Old 6th March 2019, 10:00 PM   #2571
RNMarsh is offline RNMarsh  United States
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Nice upgrades... very useful ones.




THx-RNMarsh
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Old 14th March 2019, 05:01 PM   #2572
QAMAtt is offline QAMAtt
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Thanks RNMarsh, yes agree there's a lot of value in these types of plug-ins. The next release of the QA401 software posted last night on github, and it is almost a complete re-write of the graphing and plug-in subsystem. From a code standpoint, it's greatly unified and there's a lot more code shared across the different plug-ins. After a bit more cleanup we'll publish the plug-in sources. The hardest thing to wrestle with thus far is the creeping needs for graphing flexibility, and I think we're off in a good direction on the latest release. It's far from perfect, but the foundation is there.

Here's a link to a new video showing how these plug-ins can be used to stack traces and let you see tone knob versus gain changes (for example) overlaid atop each other. The new plug-in design should make this type of task even easier.

Fast Amp Characterization

-Matt
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Old Today, 02:01 AM   #2573
1audio is offline 1audio  United States
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Attached are selftest plots of my QA401. First with a generic USB cable and then with a slightly better USB cable. Normally I would expect dropped frames or other ugly with a bad cable but NOT a major difference in the distortion pattern.

If you get bad results it may be the cable. ijn this case since nothing else was attached I could see no other possible issues and I was first worried that my QA401 had failed somehow. . . but just a funky cable. FWIW the cable shield measures about 500 milliOhms, a decent cable should be closer to 100 milliOhms.

I need to check the voltage at the QA401 end of the cable.
Attached Images
File Type: png Selftest USB cable #2.png (61.2 KB, 56 views)
File Type: png Selftest USB cable #1.png (54.7 KB, 51 views)
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Old Today, 08:02 AM   #2574
gazzagazza is offline gazzagazza  New Zealand
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Now that is interesting. I was at a presentation last week given by a manufacturer of music servers (Antipodes Audio). The owner and product designer was delivering the talk. He was very focused on getting very low noise transfer of digital signals and was able to demonstrate quite clearly sonic changes with different cables, including Ethernet and USB between server and renderer and renderer and DAC. Your results here may be relevant.

His previous working life was in data transmission in a telecommunications environment.
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Old Today, 08:26 AM   #2575
phofman is online now phofman  Czech Republic
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IIUC the USB cable serves as power supply as well. 0.5Ohm resistance at the 500mA specified power consumption = 250mV at 5V - that is not a negligible voltage drop.
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Old Today, 08:42 AM   #2576
chris719 is offline chris719  United States
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QuantAsylum QA400 and QA401
Yes, maybe the switching regulators are having issues.
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