I don’t know if this will be helpful to anyone, but I’d like to share a referral for a cheap USB hub after failing with two prior purchases. One of my computers has a weak USB supply that starves my QA403 for current. After trying a few powered hubs with 5V power supplies and watching the voltage drop to something unusable with a few connections made, I tried one with a 12V power supply–assuming maybe each port would have its own regulator, or at least the hub would be able to manage its own voltage levels across different loads.
Anyway, this cheap little device works great: https://smile.amazon.com/dp/B07Y5VWLDB?psc=1&ref=ppx_yo2ov_dt_b_product_details. Voltage levels and QA403 performance stays in spec while fast-charging a phone and playing music from another high-end sound card and powering another (just as a dummy load) and a mouse/keyboard dongle. Nothing else I tried even came close. Plus I have the added benefit of running it off of a 12V battery for portable applications.
Thanks for the referral! The powered usb adapter I use sometimes has trouble maintaining the voltage to at least 4.7V, so this may be what the Dr. ordered, and it is <$20 !
Note, VAR, that I am seeing voltage levels on this device of around 4.7V–dropping to 4.6-something when loaded with other devices. So if you have something already that works at 4.7, this may not be an improvement. My issue with other devices is that they would drop to 4.5 or less as soon as I started loading them up. They all worked fine with only the QA403 connected.
My QA402 will flash red or orange depending on how low the voltage is- probably fine at 4.7v (I did not plug it in to verify), and the only thing that would be plugged into the hub would be the QA402 so, I should not drop below 4.7v or so. If it doesn’t work better it is easy enough to return
Just wanted to let you know that I finally sprung for the hub you recommended and my QA402 voltages went from ~4.6/4.7 to a little bit over 5v! It is the only thing plugged into the hub, but that was the case for the other hub too. It plugs into a usb3 port on my PC. I like that you can switch any port OFF/ON too- thanks!
I too purchased one of the Hubs recommended here to go with the QA401 I bought to use/play with until a new model becomes available. I’ll let you know how it goes but since a few here have tested it already, it’s probably Moot! Thanks
Perry
P.S. If anybody has an unused QA403 and a 451, drop me a PM if you are interested in selling.
I’ve tested a number of USB cables along with these, and found to get a reliable connection/ high enough voltage to the QA403, a 24AWG cable is required. The shorter the better-- I’ve been using some 50cm, 60cm and 1m cables, and while they all have worked, the 1m was approaching the 4.6V threshold a bit closer than I’d like. The manual does make mention of the 24AWG cables on page 8, but it is easy to miss-- in my testing, either of the above hubs will adequately power the QA403. The RSHTech unit provided 100mV or so higher, but for my production application the more robust physical design of the StarTech (aluminium enclosure, wall-mount plate included) was a better tradeoff-- I’m not sure on the longevity of the individual port on/off buttons on the RSHTech.
When testing with 26 or 28AWG USB cables, I’ve found results to be inconsistent and would not recommend these.
Here’s a good USB cable from Monoprice. I use the 2 meter length with no issues without use of a hub. Monolith by Monoprice.
I also use the Monolith RCA cables in my main stereo system. Good stuff at a reasonable price. https://www.monoprice.com/product?p_id=33464
I have bought an Exsys EX-11234HMS USB hub. This is an industrial USB hub which is not bus powered but needs an external +9V… +24V power supply. So it does not draw current from my laptop. I connected my QA472 low noise pre-amp and my QA402 to the hub and the uplink from my hub with the laptop. As a test case I measured the PRE1 of the QA472 in +20dB gain setting, single ended. The first measurement was pretty disapointing, a lot of 50Hz hum was picked up. After several failed atempts with different cables etc. I finally ended up experimenting with the USB hubs power supply.
Here is a what I have measure, when I used the power supply which was delivered with the hub:
I was trying several other power supplies with my hub. By far the best result was with the power supply delivered with the QA461. Here is the measurement:
I have run the measurement with various +12V power supplies (including a lab power supply and they were all much worse than the QA461 power supply. This clearly shows that the power supply of the hub matters and it also shows that Matt made a very good choice for the QA461. I thought this might be interesting.
I will investigate a bit more in the coming days.
Two days later…
I have just run a few more tests. The results are different. Here is todays measurement with the power supply that came with the hub:
Nothing to complain.
I have again run measurements with different power supplies and they all showed the almost same result. I used the same cables as last time but my cabling was a bit cleaner and changing the power supply was possible without touching other cables. I think the cables and how well they make contact makes the difference. My USB hub seems to work properly and allows to make very good quality measurements. For all measurements the QA402 indicated around 4.95V @ 0.89A.
