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QuantAsylum QA400 and QA401
QuantAsylum QA400 and QA401
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Old 20th March 2019, 11:35 PM   #2581
QAMAtt is offline QAMAtt
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Join Date: Nov 2017
Location: Seattle, WA, USA
Mostly for convenience. The QA401 is small (177x44x97mm) and light (420g) and carrying it in your backpack or computer bag is easy. Plug the QA401 into a port, and you'll quickly see if the port noise is causing an issue. And if it is, then just use a powered USB hub or USB power injector with your choice of 5V adapter. That is the same as having a dedicated power supply.

But most PCs have USB ports that are usable as-is. Even a $199 fanless PC. Even the nasty desktop port shown in the previous post isn't much of a problem: You can see the noise floor of the analyzer (attached) when powered by that nasty port in the previous post: It's only a few tenths of a dB above the expected noise floor of -115.x dBV (20 KHz, no weighting).
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Last edited by QAMAtt; 20th March 2019 at 11:39 PM.
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Old Yesterday, 05:40 AM   #2582
1audio is offline 1audio  United States
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Join Date: Mar 2004
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I'll do some more methodical tests tomorrow. I used several USB ports including an external hub (that works fine with the QA101 and a Picoscope). I found several poor cables and 1 good short (1') and one good long (8') cable. If I were still selling USB cables this would be a really effective sales tool.

I'll dig deeper since its interesting to me. Also interesting is how clean the loopback is with a good cable connection.

To Do:
Several cables on a port that works with a good cable.
Several computers (I have three I can try this with) with different ports.
Measure the DCR of the ground wire and Vbus. A litle more difficult to get to.

USBIF has specific specs for voltage drop under load. I should be able to check the actual drop. I'll also set up a breakout to check for noise. Maybe I should start a cable company. Oops, been there. Not again.
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Old Today, 03:59 AM   #2583
1audio is offline 1audio  United States
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Join Date: Mar 2004
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Quote:
Originally Posted by edechamps View Post
These issues are fixed in ASIO401 1.1. Starting from that version, ASIO401 sticks with the convention that a positive sample value represents a positive voltage on the + terminal.
I just posed an issue that the ASIO format is not working with either Virtins Multi-Instument or DiAna. It seems there are a number of valid ASIO formats but not every software works with all of them.
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