# USB: startech ST4200SUBM: USB 2.0 hub ok? **URL:** \ **Category:** QA40x\ **Created:** [May 25, 2026, 9:46pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285 "2026-05-25T21:46:07Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![mkg\_el34](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@mkg\_el34](https://forum.quantasylum.com/u/mkg_el34)\ **Post date:** [May 25, 2026, 9:46pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/1 "2026-05-25T21:46:07Z")
I bought a startech ST4200SUBM USB hub for my QA403. I put 7 V on the external power source pins and confirmed it converts it to 5V on the USB port. Opening it I see it uses a DC-DC switching converter chip (MT3905), which supposedly can output 4A, which surprises me a bit, since it’s a little SMD guy, but I’m pretty sure it’s good for the current the device needs. I hadn’t thought about it being a USB 2.0 device. Spec sheet says so and it has a USB 2.0 hub chip in it sure enough. Is USB 2.0 OK bandwidth-wise? I see mention of USB 3.0 but that seems more related to the power requirements. Thanks ! ---
**Author:** ![MarkZ](https://yyz2.discourse-cdn.com/flex032/user_avatar/forum.quantasylum.com/markz/32/4269_2.png) [@MarkZ](https://forum.quantasylum.com/u/MarkZ)\ **Post date:** [May 27, 2026, 10:42am UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/2 "2026-05-27T10:42:06Z")
The USB connector on the QA403 is a USB 2.0 USB-B connector, not USB 3.0. So, you’re good. ---
**Author:** ![markg](https://avatars.discourse-cdn.com/v4/letter/m/c2a13f/32.png) [@markg](https://forum.quantasylum.com/u/markg)\ **Post date:** [May 30, 2026, 4:49pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/3 "2026-05-30T16:49:01Z")
I have found voltage at the unit is closer to 5V when using a USB C to B cable from a USB C port. Every USB C port supports at least 1.5A. Even if the hub supports high currents, individual USB A ports may not go over the 0.5A minimum for USB A 2.0 or 0.9A for USB A 3.0. USB C supports the USB 2.0 speeds with no issues. I’ve tried this with a few hubs and direct with a couple different computers. ---
**Author:** ![mkg\_el34](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@mkg\_el34](https://forum.quantasylum.com/u/mkg_el34)\ **Post date:** [May 30, 2026, 9:06pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/4 "2026-05-30T21:06:59Z")
Cool thanks. Good to know ---
**Author:** ![mkg\_el34](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@mkg\_el34](https://forum.quantasylum.com/u/mkg_el34)\ **Post date:** [May 30, 2026, 9:14pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/5 "2026-05-30T21:14:00Z")
That’s a good thought about what the hub will provide per connection. I made a breakout out of an old cable to test it. It had 24 ga wire for the power leads and I made it about 12 in long. I found that one port will provide 1.5 A (didn’t go past that). What I don’t like is that the voltage is dropping to 4.6 V at around 900 mA. The manual says the QA403 can draw 800 to 900 mA or more depending on the measurement, so I don’t like the idea of hitting the orange level if I’m doing a test that is drawing more current. I don’t know if it’s dropping purely through the 24 ga wire or the regulation is just not that good. Maybe they put a series resistor at the power output to protect from shorts. Anyway thanks for the response, good info ---
**Author:** ![markg](https://avatars.discourse-cdn.com/v4/letter/m/c2a13f/32.png) [@markg](https://forum.quantasylum.com/u/markg)\ **Post date:** [May 30, 2026, 9:44pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/6 "2026-05-30T21:44:07Z")
Every USB C to B cable provided more than 4.9V at the unit, no matter where it was connected. ---
**Author:** ![MarkT](https://avatars.discourse-cdn.com/v4/letter/m/c89c15/32.png) [@MarkT](https://forum.quantasylum.com/u/MarkT)\ **Post date:** [June 3, 2026, 5:05am UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/7 "2026-06-03T05:05:46Z")
Contact resistance in the USB connector can dominate sometimes - the springiness in old connectors can reduce, and surface tarnish (oxide) will only increase with time. Manufacturer’s insertion-cycle ratings are only for a new connector in a dry atmosphere, not real-world use with finger-grease, humidity and long periods between uses. So suspect any old lead to be problematic if not visually inspected and perhaps cleaned / burnished. Cheap unbranded connectors (and thus cables) are unlikely to have any datasheet and are pot-luck. They can also have CCA wire which is even worse (brittle, doesn’t crimp well, less current handling). ---
**Author:** ![mkg\_el34](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@mkg\_el34](https://forum.quantasylum.com/u/mkg_el34)\ **Post date:** [June 6, 2026, 11:41pm UTC](https://forum.quantasylum.com/t/usb-startech-st4200subm-usb-2-0-hub-ok/2285/8 "2026-06-06T23:41:31Z")
I went back and made an extra measurement. at load: 1.02 A, 4.62 V at adjoining USB connector on hub: 4.82 V Losing 0.2 V. At leat 0.1 more than I would expect from 24 in of 24 ga wire. Suspect contact resistance or cheap wire, as you say.