LG UltraFine 4K and 5K: Yes you can connect it to Windows computers via DP!!!

[Nitram1420]

Hi there,
First of all thank you all very much for the amazing amount of knowledge concentrated on this thread, which I read carefully several times.
I recently purchased a second hand Ultrafine 5K (first gen, so TB only) which I totally love when used with my macbook pro.
Like many here, I also have a work laptop provided by my employer, and I would love to use the Ultrafine (even in 4K) with this Windows laptop. The laptop has thunderbolt but it is disabled and I cannot enter the BIOS. USB-C works fine and I use it with a USB-C/HDMI adapter with another screen.
If I understand well, in order to be able to use the Ultrafine, I need
- a bi-directional USB-C to DisplayPort adapter
- An Alpine-Ridge or Titan-Ridge
- a PCI16x riser and its power supply.
So I bought all that and...nothing on screen.
The usbc-DP works fine when connected to a DP screen.
The DP output of the Titan-Ridge (v2) works just fine too, but connecting the thunderbolt display to the thunderbolt ports does not do anything at all.
I have also jumped the TB header on the Ridge (Force Power) but to no avail. I also installed the Ridge in a PCI slot of my gaming PC, connecting the GPU directly to the Ridge (so without USB-C to DP adapter), but to no avail; the screen does not even turn on.
Any suggestion as to what I could try next? I'd really love to use the Ultrafine as my main display...

 

[etc]

Hi there,
First of all thank you all very much for the amazing amount of knowledge concentrated on this thread, which I read carefully several times.
I recently purchased a second hand Ultrafine 5K (first gen, so TB only) which I totally love when used with my macbook pro.
Like many here, I also have a work laptop provided by my employer, and I would love to use the Ultrafine (even in 4K) with this Windows laptop. The laptop has thunderbolt but it is disabled and I cannot enter the BIOS. USB-C works fine and I use it with a USB-C/HDMI adapter with another screen.
If I understand well, in order to be able to use the Ultrafine, I need
- a bi-directional USB-C to DisplayPort adapter
- An Alpine-Ridge or Titan-Ridge
- a PCI16x riser and its power supply.
So I bought all that and...nothing on screen.
The usbc-DP works fine when connected to a DP screen.
The DP output of the Titan-Ridge (v2) works just fine too, but connecting the thunderbolt display to the thunderbolt ports does not do anything at all.
I have also jumped the TB header on the Ridge (Force Power) but to no avail. I also installed the Ridge in a PCI slot of my gaming PC, connecting the GPU directly to the Ridge (so without USB-C to DP adapter), but to no avail; the screen does not even turn on.
Any suggestion as to what I could try next? I'd really love to use the Ultrafine as my main display...

How many DP cables you connect to Titan Ridge?

 

[Nitram1420]

How many DP cables you connect to Titan Ridge?

Only one, since the USB-C to DP has only one output.
I've just tried with 2 (in my windows gaming machine, using the DP ports of its GPU) and it's exactly the same. Simply nothing.

 

[Nitram1420]

Alright, I read somewhere that pin 4 of the header also supplies the required voltage to pull pin 1 high, so I used this one instead. Magically, the AIC eventually turned on, and I got a beautiful 5K from my gaming PC.
I then used the USB-C to DP from my work laptop, and there too it was working, giving me 4K (and a bit more actually).
I then tried again the card with the PCI riser but it didn't work. I was suspecting the power supply to be faulty (despite reading correct voltages) so I ended up using an ATX power supply. Nothing. I also used the power supply 3.3V output and a 10K resistor in series to pull pin 1 high, but no success.
It is now back in a PCI slot of my gaming PC, exact same setup as when it worked, but no, nothing at all.
I have tried all possible configurations for the connections, also unplugged and replugged the display from the mains.
What else can I try? Any suggestion?

 

[Nitram1420]

So the issue is to find the right startup sequence, which I have not been able to figure out yet, but when it works, it works really well.
I got brightness control with ScreenBright.
And... Using CRU and the information gathered in this thread, I now have 5K38!

 

[etc]

Only one, since the USB-C to DP has only one output.
I've just tried with 2 (in my windows gaming machine, using the DP ports of its GPU) and it's exactly the same. Simply nothing.

Hmm, you're doing something wrong, you don't need USB-C to DP cables to connect UltraFine via Titan Ridge. Titan Ridge card has two DP inputs and two USB-C/TB outputs, also there's a regular DP port, but it's not supposed to be used.

For 5K UltraFine requires two DP 1.2 streams (that means two DP to mini-DP cables and both are used to connect GPU and Titan Ridge) and TB3 cable that comes with the display. You may not get boot screen if you connect both DP cables before booting, so try to connect the second cable after booting (that how it worked for me, a bit annoying actually).

 

[Nitram1420]

Hmm, you're doing something wrong, you don't need USB-C to DP cables to connect UltraFine via Titan Ridge. Titan Ridge card has two DP inputs and two USB-C/TB outputs, also there's a regular DP port, but it's not supposed to be used.

The laptop with which I want to use the UltraFine does not have DP ports, only USB-C (Actually TB4 but TB is disabled at BIOS level, to which I do not have access). So I use an adapter to output DP from USB-C and therefore hookup the laptop to one of the DP inputs of the Titan Ridge.

For 5K UltraFine requires two DP 1.2 streams (that means two DP to mini-DP cables and both are used to connect GPU and Titan Ridge) and TB3 cable that comes with the display. You may not get boot screen if you connect both DP cables before booting, so try to connect the second cable after booting (that how it worked for me, a bit annoying actually).

5K60 requires two DP1.2 streams, but 5K38 works perfectly well with only one. For my coding work, 5K38 is more than enough.

Cold boots remain an issue. The TitanRidge will not activate unless it is in an actual PCIe slot, or the riser I use is indeed connected to a PCIe slot. Once booted up (after a lot of playing around with the connections), all the TitanRidge seems to need is power from the PCIe riser. The PC offering the PCIe slot can be turned off and everything keeps on working properly; even the laptop can be turned off then back on with no problem.

A second Ultrafine 5K (2nd generation) will arrive here in the next few days. I bought it new this time as their prices have significantly dropped lately and I have not found a better display yet; I find it really hard to come back to 'regular' screens after having used 5K with 200% scaling for a while. My intention then will be to use Club3D's CSV-1550 (MST hub) to try and use both screens over TB3 at 5K38. Of course, this is still for my work laptop with one USB-C port only.

Also I should receive another PCIe riser today, which hopefully will allow booting up the Titan Ridge without the help of an actual PCIe slot.

 

[petervivian]

Do you know of any other software or apps that are compatible with Windows 10 to adjust the brightness of the LG Ultrafine monitor, besides the LG Ultrafine Brightness app from the Microsoft App store? I previously used this app in 2020, but it no longer works. When I attempt to run the app, a window appears but it is blank and the app immediately closes.

 

[currocj]

can someone explain the steps for 5k38/9? I have a motherboard with a single dp in port so I only see 3840x2160 in the resolutions available drop down.

Windows 11
Motherboard: ASUS ProArt B550 Creator
CPU: AMD 5600G
GPU: RTX 3070 FE
Cable: Bi-directional full DP to DP from 3070 to DP in port on m/b backplate
Desired Resolution: Full 5K (only getting 3840x2160 in drop down)

 

[joevt]

can someone explain the steps for 5k38/9? I have a motherboard with a single dp in port so I only see 3840x2160 in the resolutions available drop down.

Windows 11
Motherboard: ASUS ProArt B550 Creator
CPU: AMD 5600G
GPU: RTX 3070 FE
Cable: Bi-directional full DP to DP from 3070 to DP in port on m/b backplate
Desired Resolution: Full 5K (only getting 3840x2160 in drop down)

Use Nvidia Control Panel to add a custom timing. Try CVT-RB calculation. CVT-RB2 might work or it might not. CVT-RB2 would allow for slightly higher refresh rate.

Or use CRU to create the custom timing (which is what I would do for AMD GPU since I don't trust Radeon Software). Custom timings created by CRU are per GPU port and display vendor/product, which means the custom timing only works for that display and that GPU port. Edit the display name so that it includes the GPU port that its connected to and you'll know its a custom timing.

 

[Nitram1420]

2x5K38 with my work laptop!

So here is the situation and a quick recap:

My work laptop is an HP ZBook Power G8 running Win 10. It has one TB4 port where TB seems to be BIOS limited for security reasons. DisplayPort does work on that port, and there is an HDMI port too.
I now have two Ultrafine 5K monitors, one of each generation.

Using thunderbolt the screen does not turn on and Windows reports a "Thunderbolt functionality may be limited" message.

Using USB-C on the new screen I get a default 4K60 and using CRU I get 5K38 and speakers, camera, etc, work fine. Super happy with it.

For the 1st gen Ultrafine, which I got first, I acquired a CAC-1557 UCB-C to DP adapter and a Titan Ridge AIC.
I have not been able to initialize the Titan Ridge without an actual PCIe connection. I tried 3 different risers, including a double one equipped with an ASM1182e chip, but to no avail. Once initialized though, I can disconnect the riser from the donor PC.
This setup works very well, with a default 4K60 and the same 5K38 using CRU but obviously no USB functionalities at all.

I then decided to go further in my quest to use the two displays, and acquired a CSV-1550 which has 3 DP outputs so as to connect two to the AIC. This consistently gives me one display at 5K60, but never two at 4K60. Also, I have not been able to change the default frequency to less than 39; the screen will not turn on and Windows keeps on saying the frequency is 60 despite the changes. After a few attempts, the graphics drivers eventually crash leaving me with no screen at all and the need to brutally shutdown the laptop. Also I noticed that initializing the CSV-1550 is a lot harder and requires several reconnections, sometimes even the need to plug something into the DP out port of the AIC for it to start working (the adapter has LEDs on each port to indicate activity, they remain off unless I do that). I have no idea what I could be doing wrong or even how to troubleshoot, since the second screen is never discovered by the system.

Finally, I ordered a CAC-1336 to convert HDMI to UCB-C. I could then use one screen with thunderbolt through the CAC-1557 and the AIC and the other one with HDMI via the CAC-1336.

And... IT WORKS!
So I finally have 2 Ultrafines 5K running at 5K38.

Big big thanks to @joevt for his acurate and information rich posts on various forums!
But I am not totally finished... Is there any way I could use the CSV-1550 to drive those two monitors with thunderbolt?

Also, I am considering selling the old-gen screen to replace it with the new one, so as to skip the AIC and be able to use the camera and speakers... This is definitely what I would do if I cannot use the CSV-1550 as it is a lot less messy. Had I known all that from the start, I would have returned the old gen Ultrafine and bought a new one.

Correction: The CAC-1336 does pass USB data through, so the Ultrafine is fully functional!

 

[joevt]

I then decided to go further in my quest to use the two displays, and acquired a CSV-1550 which has 3 DP outputs so as to connect two to the AIC. This consistently gives me one display at 5K60, but never two at 4K60.

Which LG UltraFine 5K display works at 5K60 using the CSV-1550/AIC? First gen, 2nd gen, or both?

I would use AllRez on an Intel Mac to verify that the CSV-1550 DisplayPort MST hub supports DSC. Some or All MST hubs that support DSC might not be able to decompress to 10bpc.

An MST hub should be able to do three 4K60 displays simultaneously (at 8bpc since most/all? MST hubs don't decompress 10bpc). I guess you need to make sure that 8bpc is chosen in Nvidia control panel.

Also, I have not been able to change the default frequency to less than 39; the screen will not turn on and Windows keeps on saying the frequency is 60 despite the changes. After a few attempts, the graphics drivers eventually crash leaving me with no screen at all and the need to brutally shutdown the laptop.

I'm not sure what you mean by "change the default frequency to less than 39". Do you mean that modes like 30Hz, 31Hz, ... 38Hz don't work?

Also I noticed that initializing the CSV-1550 is a lot harder and requires several reconnections, sometimes even the need to plug something into the DP out port of the AIC for it to start working (the adapter has LEDs on each port to indicate activity, they remain off unless I do that). I have no idea what I could be doing wrong or even how to troubleshoot, since the second screen is never discovered by the system.

Do you have normal/not-Thunderbolt displays to test?

Is there any way I could use the CSV-1550 to drive those two monitors with thunderbolt?

Seems like you setup everything correctly but Thunderbolt displays that have no buttons have issues. It's kind of strange that the inputs to the TB3 AIC are coming from a MST hub but I don't see why that wouldn't work.

Also, I am considering selling the old-gen screen to replace it with the new one, so as to skip the AIC and be able to use the camera and speakers... This is definitely what I would do if I cannot use the CSV-1550 as it is a lot less messy. Had I known all that from the start, I would have returned the old gen Ultrafine and bought a new one.

Correction: The CAC-1336 does pass USB data through, so the Ultrafine is fully functional!

The first gen display doesn't have USB support (camera, audio, etc) because your work won't let you change the BIOS on the work laptop to let you use Thunderbolt devices (tunnelled PCIe) ? If your laptop has an accessible M.2 slot, then you could connect the AIC to that but it would be messy and probably wouldn't work without some hacks.

 

[GeneParm]

I am in sort of a unique situation and I hope someone can help me. I currently own a 27inch LG 5k(27MD5KL) && a studio display. If anyone knows if there is a windows laptop out there that I could buy that would let me use both these monitors please let me know. Ideally one that would work the most seamless (if possible).

Thank You

 

[joevt]

I am in sort of a unique situation and I hope someone can help me. I currently own a 27inch LG 5k(27MD5KL) && a studio display. If anyone knows if there is a windows laptop out there that I could buy that would let me use both these monitors please let me know. Ideally one that would work the most seamless (if possible).

I wonder if the Framework laptop can do it. It has four Thunderbolt 4 ports and can output to 4 displays (the internal display counts as 1, the LG UltraFine 5K counts as 2, the Studio Display counts as 1). The Intel GPU can output up to 8K60 but there might be a limit to the number of pixels per second total that it can output (I don't think it can output to four 8K60 displays for example - but I haven't searched for documentation about that).

 

[GeneParm]

I wonder if the Framework laptop can do it. It has four Thunderbolt 4 ports and can output to 4 displays (the internal display counts as 1, the LG UltraFine 5K counts as 2, the Studio Display counts as 1). The Intel GPU can output up to 8K60 but there might be a limit to the number of pixels per second total that it can output (I don't think it can output to four 8K60 displays for example - but I haven't searched for documentation about that).

Is this the only solution? I am in need of the windows machine for graphics programming. Looking for something with a dedicated gpu in it too. But considering all options.

I am under the impression any machine with 2 thunderbolt 4 ports would work, hoping someone here can give me confirmation.

 

[currocj]

Decided to swap to a motherboard with the TB header and get a TB 4 card. 5K 60Hz out of the box. Easy Peasy.

Motherboard: ASUS ROG STRIX B550-F Gaming Wifi II
Add on Card: ASUS ThunderboltEX 4
GPU: RTX 3070

Everything just works. Audio, usb hub, camera. Just need to figure out brightness, wasn't there an app for that?

 

[joevt]

Is this the only solution? I am in need of the windows machine for graphics programming. Looking for something with a dedicated gpu in it too. But considering all options.

I am under the impression any machine with 2 thunderbolt 4 ports would work, hoping someone here can give me confirmation.

In pre Ice Lake Intel Mac laptops, the discrete AMD GPU is always connected to the discrete Thunderbolt controllers so Thunderbolt connected displays are always controlled by the discrete AMD GPU.
https://en.wikipedia.org/wiki/MacBook_Pro_(Intel-based)#Touch_Bar_(2016–2020)
For connecting a Studio Display, the one with Coffee Lake CPU and Navi graphics (AMD 5300M or 5500M) would be best since that GPU supports DSC. The Studio Display can be connected to a GPU that doesn't support DisplayPort 1.4 and DSC, but in that case it uses up two DisplayPort connections instead of just one, just like the LG UltraFine 5K.

The Framework Laptop is an Alder Lake based laptop. Tiger Lake would also work. The GPU is integrated and is connected to the integrated Thunderbolt 4 controllers.
https://knowledgebase.frame.work/external-monitor-support-on-the-framework-laptop-rk5GVUwyY

The problem with discrete GPUs in a PC laptop is that they are ?often? not connected to a Thunderbolt controller. The discrete GPU in a PC laptop can still be used, but it must send its pixels to the Intel integrated GPU that is connected to the Thunderbolt controller. Maybe you won't notice a performance problem. Use the Device Manager, view by Connection, to see what GPU a display is connected to.

One solution may be to add an external GPU but they don't have a downstream Thunderbolt port to achieve 5K60 from an LG UltraFine 5K except the BlackMagic eGPU or the Sonnet eGPU Breakaway Puck RX 5550 XT/5700. The downstream Thunderbolt port is only supported in macOS. https://www.sonnettech.com/support/kb/kb.php?cat=590&expand=_a2&action=b1127#b1127

Without Thunderbolt, you can get 4K60 from the LG UltraFine 5K, or 5K39 with a custom timing.

 

[TheSheikh]

Hi I need some help please. I have a LG27MD5KA-B
I have a Legion T730-28ICO Desktop (Lenovo) - Type 90JF
NVIDIA®GeForce RTX™2080 SUPER™ (Only 3 DVI and one HDMI Port)

I purcahsed a Wacom Link Plus INF-A143 (Wacom Link Plus for Cintiq Pro 13/16 (ACK42819))
Purchased DVI to Mini Dsplay Port cable

Amazon Basics Mini DisplayPort to DisplayPort Display Cable, 4Kx2K, Gold-Plated Plugs, 6 Foot, Black

Amazon Basics 4K Mini DisplayPort to DisplayPort Cable - 6 Feet

www.amazon.com

CABLEDECONN 1M 3.3FT Mini DP to DisplayPort 8K Cable 8K(7680x4320)@60Hz 4K@144Hz DisplayPort 1.4 Bi-Directional Transmission DisplayPort to Mini DisplayPort 8K Cable

CABLEDECONN 1M 3.3FT Mini DP to DisplayPort 8K Cable 8K(7680x4320)@60Hz 4K@144Hz DisplayPort 1.4 Bi-Directional Transmission DisplayPort to Mini DisplayPort 8K Cable

www.amazon.com

Also tried with HDMI
(I did plug in the USB to my PC from the Wacom Link Plus)

I am not able to get it to work. When I plug everyting in my dekstop gets a message saying "thunderbolt device functionality maybe limited"

I can't seem to get my PC to detect the Wacom Link Plus. I tried to download drivers by going to https://www.wacom.com/en-us/support/product-support/drivers. I could not find Wacom Link Plus on the list so download the Windows Driver when you scroll down. When I open the Wacom Center app it says no device detected. I am not sure what I am doing wrong. I have swapped out many cables and same issue.

Can someone please help.

 

[joevt]

Hi I need some help please. I have a LG27MD5KA-B
I have a Legion T730-28ICO Desktop (Lenovo) - Type 90JF
NVIDIA®GeForce RTX™2080 SUPER™ (Only 3 DVI and one HDMI Port)

I purcahsed a Wacom Link Plus INF-A143 (Wacom Link Plus for Cintiq Pro 13/16 (ACK42819))
Purchased DVI to Mini Dsplay Port cable

Amazon Basics Mini DisplayPort to DisplayPort Display Cable, 4Kx2K, Gold-Plated Plugs, 6 Foot, Black

Amazon Basics 4K Mini DisplayPort to DisplayPort Cable - 6 Feet

www.amazon.com

CABLEDECONN 1M 3.3FT Mini DP to DisplayPort 8K Cable 8K(7680x4320)@60Hz 4K@144Hz DisplayPort 1.4 Bi-Directional Transmission DisplayPort to Mini DisplayPort 8K Cable

CABLEDECONN 1M 3.3FT Mini DP to DisplayPort 8K Cable 8K(7680x4320)@60Hz 4K@144Hz DisplayPort 1.4 Bi-Directional Transmission DisplayPort to Mini DisplayPort 8K Cable

www.amazon.com

Also tried with HDMI
(I did plug in the USB to my PC from the Wacom Link Plus)

I am not able to get it to work. When I plug everyting in my dekstop gets a message saying "thunderbolt device functionality maybe limited"

I can't seem to get my PC to detect the Wacom Link Plus. I tried to download drivers by going to https://www.wacom.com/en-us/support/product-support/drivers. I could not find Wacom Link Plus on the list so download the Windows Driver when you scroll down. When I open the Wacom Center app it says no device detected. I am not sure what I am doing wrong. I have swapped out many cables and same issue.

Can someone please help.

The LG27MD5KA only supports Thunderbolt input.
The LG27MD5KL can work with non Thunderbolt input up to 4K60 or 5K39. 5K60 requires Thunderbolt input.

If your desktop doesn't include Thunderbolt, then maybe you could add a Thunderbolt 3 add-in card. However, the add-in card might not be compatible with your motherboard if it doesn't have a Thunderbolt header.

 

[TheSheikh]

The LG27MD5KA only supports Thunderbolt input.
The LG27MD5KL can work with non Thunderbolt input up to 4K60 or 5K39. 5K60 requires Thunderbolt input.

If your desktop doesn't include Thunderbolt, then maybe you could add a Thunderbolt 3 add-in card. However, the add-in card might not be compatible with your motherboard if it doesn't have a Thunderbolt header.

I ordered the adapter but then realized my motherboard does not have a extra PCI slot... just one for the graphics card. Would I have any other options? Is there a new graphics card I can buy that has a Thunderbolt 3 option? I really don't want to get a whole new desktop or get a new monitor. I found this one for super cheap and want to try and keep it. I did try a bidirectional cable and that did not work.

 

[joevt]

I ordered the adapter but then realized my motherboard does not have a extra PCI slot... just one for the graphics card. Would I have any other options? Is there a new graphics card I can buy that has a Thunderbolt 3 option? I really don't want to get a whole new desktop or get a new monitor. I found this one for super cheap and want to try and keep it. I did try a bidirectional cable and that did not work.

Does your motherboard have a spare NVMe slot?

Connecting Thunderbolt 3 add-in card to NVMe slot or powered riser is a possibility but probably won't work without some investigation and hacking. You should probably just get a different display.

 

[Nitram1420]

Which LG UltraFine 5K display works at 5K60 using the CSV-1550/AIC? First gen, 2nd gen, or both?

Apologies for not having responded sooner; I had a bit of actual work to do...

If I remember well, both displays would work with the CSV-1550/AIC but only individually. Using custom timings with CRU would not work at all and would eventually crash the display drivers.

I would use AllRez on an Intel Mac to verify that the CSV-1550 DisplayPort MST hub supports DSC. Some or All MST hubs that support DSC might not be able to decompress to 10bpc.

An MST hub should be able to do three 4K60 displays simultaneously (at 8bpc since most/all? MST hubs don't decompress 10bpc). I guess you need to make sure that 8bpc is chosen in Nvidia control panel.

Considering how difficult and inconsistent it was to initialise the CSV-1550/AIC, I decided to return it and use only the CAC-1557 instead. I really don't need 5K60 and 5K38 is just fine for what I do.

I'm not sure what you mean by "change the default frequency to less than 39". Do you mean that modes like 30Hz, 31Hz, ... 38Hz don't work?

I made it more complicated than required. I simply meant that anything that is not default 5K60 does not work and ends up freezing the computer.

The first gen display doesn't have USB support (camera, audio, etc) because your work won't let you change the BIOS on the work laptop to let you use Thunderbolt devices (tunnelled PCIe) ? If your laptop has an accessible M.2 slot, then you could connect the AIC to that but it would be messy and probably wouldn't work without some hacks.

That's a no-go on my work laptop.

In the meantime, I seem to have destroyed the AIC while trying a power supply and it really irritated me. Since the CAC-1336 works fine (although sometimes tough to initialise too, with only 1080p for a while...), I decided to put up for sale the first generation display and buy a second second gen one, so one will be over USB-C and the other HDMI via the CAC-1336, and running both at 5K38. Unfortunately the market for a second-hand TB3 only display is really small so the screen is still here, unless I accept to lose a lot of money on it...
I may end up buying a new AIC and something that looks very much like your IT-GO case: https://fr.aliexpress.com/item/3282....0.0.769a378dkZz8sU&mp=1&gatewayAdapt=glo2fra
I just hope that with that PCIe riser, the AIC will boot up properly without an actual PCIe connection. Anyway, I have not decided what to do yet.

 

[Lacky]

Is it possible to connect the LG UltraFine 5K Display with NVIDIA Surround at all?

Hi all, just following up on my reply from a couple pages back. Does anyone have any success with this at all?

I setup a new thread specifically for this particular issue if anyone has any suggestions:

https://forums.macrumors.com/threads/does-the-lg-ultrafine-5k-support-nvidia-surround.2349128/?post=31210113#post-31210113

 

[Nitram1420]

So I managed to sell the LG27MD5KA reasonably well and acquired a second LG27MD5KL, so the Windows laptop can use both screens at once, one connected to the USB-C port, and the other the HDMI port via the CAC-1336. I have weird sound issues with the CAC-1336 (and windows complains it is not USB3) but it's all good with the USB-C connection.

 

[joevt]

I have weird sound issues with the CAC-1336 (and windows complains it is not USB3) but it's all good with the USB-C connection.

Does Windows complain that the USB-C connection is not USB3? What's the actual message from Windows in either case?

Not sure why they would have different sound quality. Both are connected using USB 2.0 since you're not using Thunderbolt. Did you try switching the displays to see if the issue is with the display instead of the CAC-1336?