Image quality through HDMI-VGA converter

1

I’m using a pair of HDMI-VGA converters to connect my work laptop, via a docking station (and DVI-HDMI converters - one port is DVI-I, one is DVI-D), to the VGA ports of my monitors (AOC e2250Swda).

The result is usable but washed out - the fine grey background grids on tools like gliffy, or most of the detail on Google maps, or the grey highlighting that many tools use to show focus, disappears altogether on the monitors connected with these converters. If I replace one of them with a VGA lead directly to the laptop (it only has a single VGA out) the image looks as it should. No amount of monitor adjustment helps. Digital inputs to these monitors from the docking station are also fine.

Is this an inherent aspect of these converters, or can it be resolved?

2

Hi Adam,

Thanks for contacting Plugable! Sorry to hear that your display is having issues with our HDMI-VGA cable.

In our experience, the HDMI-VGA cable quality should be good out of the box.

First troubleshooting steps:

  1. What is the exact make and model of docking station?
  2. Does the issue still occur if you connect directly from an HDMI port on a computer to the VGA port on the monitor (without the docking station and DVI converters in the mix)?
  3. Does the issue still occur on VGA ports of other monitors?

Please contact us at support@plugable.com and we can try some basic troubleshooting and send you a replacement cable to eliminate any possible defects.

Thanks,
Jordan
Plugable Technologies

3

Hi Jordan,

  1. Docking station is a Lenovo Thinkpad USB3.0 Dock (http://www3.lenovo.com/gb/en/accessor…).

  2. Laptop does not have an HDMI port. I will try with my main PC, but it will need to be later today - I’ll update my answer then. I *have* tried in the past using a Plugable USB3.0 HDMI adapter (http://plugable.com/products/usb3-hdm… - plugged in to the laptop directly) and saw the same behaviour.

  3. I have 2 monitors - same model - and 2 cables. These are the only monitors I have available for testing.

To your last point: I’m using 2 of these cables (I recently bought a second one) and they both display the same behaviour. I’m not looking for a replacement.

4

Hi Adam,

Thanks for the feedback. Sounds tricky! I think testing with your main PC should help us isolate the behavior.

If this is an urgent problem to solve, please email support@plugable.com with your findings as Plugable email support tickets have much faster resolution times than these forum posts.

Thank you,
Jordan
Plugable Technologies

5

Hi Jordan,

Apologies for the delay.

For reference, I used the Gliffy online editor at https://www.gliffy.com/go/html5/launch as this provides a perfect example of the behaviour I’m describing - essentially, the background guide-lines can’t be seen (or, at least, only very faintly).

I tried my main computer (NVidia GeForce GTX 970), using DVI-DVI, HDMI-VGA, DVI-HDMI-VGA. I tried the Thinkpad dock using DVI-DVI, DVI-HDMI-VGA and DVI-VGA-VGA (using a DVI-A to VGA analogue converter). Finally, I also tried a direct VGA-VGA link from the Lenovo laptop itself. The results are in…:

Main computer; DVI-DVI: background lines clear;
Main computer; HDMI-VGA: background lines very faint;
Main computer; DVI-HDMI-VGA: background lines very faint;
Lenovo dock; DVI-HDMI-VGA: background lines very faint;
Lenovo dock; DVI-DVI: background lines clear;
Lenovo dock; DVI-VGA-VGA: background lines clear;
Lenovo laptop; VGA-VGA: background lines clear.

That seems to pretty unequivocally point to the HDMI-VGA adapters. Note that this is *two* adapters tried across two monitors. The only experiments not repeated across both monitors were the VGA-VGA ones, due to logistics (length of cable!).

It’s not a super-urgent issue for me - I’ve been using the cables like this for ages. At some stage I’m going to upgrade the monitors to ones with dual digital inputs, and I’ll switch to using HDMI cables then. I was just interested to know if you’d seen it and if you had any hints or tips on how to improve their performance.

6

Hi Adam,

Thanks for the additional info, very helpful. I agree that since the behavior is the same without the docking station in the mix, this isolates the behavior to some interaction between your computers, monitors, and the two Plugable products.

Other troubleshooting variables to check:

  1. If possible, it would be a good data point to know if this issue can be reproduced on a third monitor. Perhaps a monitor at work or a friend’s house?

  2. Check for any driver updates for your graphics cards in both computers

  3. Check for any BIOS updates for both computers

  4. Try your monitor’s auto-adjust settings (see page 48 of the PDF link below):
    http://www.aocmonitorap.com/upload_fi…

Just want to be upfront about the possibility that there may be some incompatibility at play here that we won’t be able to solve by troubleshooting. So if the gridline behavior is a dealbreaker for you, feel free to shoot us an email at support@plugable.com and we’d be happy to start the return for refund process.

Thanks!
Jordan
Plugable Technologies

7

Hi Jordan,

About to go on holiday, so won’t have a chance to check this behaviour with another monitor for a few weeks. However, here’s what I’ve already tried:

  • Drivers up to date in main computer; drivers in laptop not so easy, as this is a work laptop and I don’t have enough privilege to easily update them (well, I can, but I’ll get an admonishment!);
  • Ditto BIOS;
  • Auto-adjust already tried.

Out of interest, how could it be a monitor issue if the VGA signal from other sources is OK? There’s no handshake of any kind, right?

Thanks for your assistance - Adam…