• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Significant static squelching noise with VTV 1ET400A

jd_cincy

Member
Joined
Feb 2, 2022
Messages
22
Likes
20
I purchased a VTV Purifi amp in February to add to my office HT. Prior to this amplifier, I used the amps in a Denon 4311ci and I've never had any noise / static issues in the past. All my office equipment is plugged into an APC UPS model BN1500M2 (Amp, Receiver, PC), although only the PC is on battery. At the time I set it up, I had significant static (squelching / squealing) during playback from all sources and all volumes. I worked with the owner of VTV and after replacing the RCA->XLR cables and trying some other things, which reduced the static slightly, we eventually isolated the issue to the AudioGD DAC. Any time it was plugged into the receiver via RCA, I had static, whether I was listening to that input or not. Since I didn't use that input all that much the fix was to unplug it and just be happy using the sound card toslink output to the receiver. Without this issue, the noise floor is low enough I can't discern any at all.

Initial Signal Path -
PC -> Creative Labs Z/XR -> Toslink -> Denon 4311ci
AudioGD NFB 11.28 -> RCA -> Denon 4311ci

That was all well and good until today, when I decided to try to plug my GPU into the receiver via HDMI. The goal here was to remove the compressed 5.1 audio from optical and use the built in Dolby / DTS encoder on the graphics card. When plugging in HDMI, the static is back (I've tried multiple cables). So now I'm at 2 different sources that cause static, which leads me to believe this is an issue with the amplifier (or possibly my receiver). Prior to being used in my office, the receiver was on family room HT duty with many inputs (Phono, HDMI, optical) and had the front 3 speakers of a 7.2.2 on an external amp and never had any static problems.

Anyone have any ideas what could be causing this horrible noise? This isn't going to be a viable setup if I can only use 1 toslink input.

Edit: I used an outlet tester and confirmed the outlet is properly grounded. My office is also on a dedicated circuit at the breaker.

Amp Details -
VTV AMPLIFIER Stereo Purifi Audio 1ET400A Amplifier
  • Input Buffer: Stock Hypex Factory Buffer
  • 12V Trigger: 12V Trigger Option
  • Binding Post Option: Default Binding Post
 
Last edited:
F

freemansteve

Guest
Is there a way test without the PC? PCs are often a source of noise that gets picked up by other kit.

I don't know what the rest of the kit is, but do you have any device that has an input with nothing connected to it, that feeds output tha is connected into any other device? Something must be acting as an antenna. Could still be faulty cable or a poor connector. Try swapping any phono-RCA-type connectors for some cheap new ones.
 
OP
J

jd_cincy

Member
Joined
Feb 2, 2022
Messages
22
Likes
20
Thank you for the response, I've been trying to isolate by removing devices, but no luck so far. What I've noticed is that the squealing happens most often when I'm moving the mouse, like dragging a window across the desktop is almost guaranteed to cause it. I've eliminated at least the wireless portion of the mouse input from being the culprit by unplugging the mouse dongle and using a wired connection, so it's possible it's a PC system issue.

I'll try to connect my laptop to the HDMI and see if that causes similar static later today.

Peripherals include -
  • USB to headphone DAC / Amp
  • USB dongle for wireless headset (Audeze)
  • USB dongle for mouse (Logitech)
  • USB bluetooth dongle (Asus)
  • Displayport x2 Monitors
  • USB Keyboard and Tenkey
  • 5mm audio cable to Modmic
 

Swtoby

Active Member
Joined
Jun 13, 2018
Messages
168
Likes
254
If your gear is near a wireless router that might be an issue. I was getting an annoying noise also, but I was able to stop it by relocating the router.
 

Doodski

Grand Contributor
Forum Donor
Joined
Dec 9, 2019
Messages
14,711
Likes
14,410
Location
Canada
What I've noticed is that the squealing happens most often when I'm moving the mouse, like dragging a window across the desktop is almost guaranteed to cause it.
I've experienced this same issue with a ASUS motherboard. The new and better motherboards are virtually silent. The manufacturers now go to lengths to make the MB's not make noisy stuff. 7+ layer PCB's with shielding between layers and additional metal shielding around IC's. You are going to have to divide and conquer to find the root of this issue.
 

tonycollinet

Major Contributor
Joined
Sep 4, 2021
Messages
3,036
Likes
4,573
Location
UK/Cheshire
This is almost certainly ground loop noise. PC's are terrible for generating this. When your PC is electrically isolated (connected only by Toslink) then there is no problem. As soon as you make an electrical connection (HDMI) then you have a loop from the PC earth through the reciever, and via your RCA to XLR cables, to the VTV amp, and back to earth through it's power connection. Then you have a powerful desktop PC with GPU generating all sorts of stray magnetic fields that couple into the ground loop and cause the noise. The noise is actually being injected in the unbalanced connection between the receiver and the amp.

The good news this is not a fault in any of the kit. The bad is that it's not that easy to solve without a balanced connection available between receiver and amp.

Suggestions to try to improve:
Plug PC, receiver and amp into the same socket, or power strip.
Connections between receiver and amp to be made as short as possible. You might need to build the interconnect yourself for that - only as long as absolutely needed.

Then minimise the area of the loop. Rec-amp interconnect routed close to amp power. Amp power to be run close to pc power back to the socket.

But ALL other PC cables (especially monitor graphics) to be separated from all audio kit as much as possible. Your problem here is the audio HDMI lead. It is part of the ground loop, but plugged into the worst case PC component for noise.



By the way - you can check this theory if you have or can borrow a laptop with HDMI out. Use that on battery as a source instead of your PC - my guess is that will not have any ground loop/noise problems - because it has no connection to earth.
 

tonycollinet

Major Contributor
Joined
Sep 4, 2021
Messages
3,036
Likes
4,573
Location
UK/Cheshire
Oh - and how are your RCA to XLR connected. You might get an improvement if you use the method of connecting the RCA screen both to the XLR Screen wire AND the XLR cold wire (via a resistior matching the output impedance of the receiver) at the reciever end, and not connect the cold pin to screen at the amp end. So running 3 connections - so called pseudo balanced as shown in the pictures here:

 
Last edited:
OP
J

jd_cincy

Member
Joined
Feb 2, 2022
Messages
22
Likes
20
I've experienced this same issue with a ASUS motherboard. The new and better motherboards are virtually silent. The manufacturers now go to lengths to make the MB's not make noisy stuff. 7+ layer PCB's with shielding between layers and additional metal shielding around IC's. You are going to have to divide and conquer to find the root of this issue.
Hopefully this is not the cause. My mobo is a ROG Crosshair VIII Hero, only ~1 year old. I'll be upgrading again in a year, so if it winds up being the issue, I guess I'll live with toslink for another year.
 
OP
J

jd_cincy

Member
Joined
Feb 2, 2022
Messages
22
Likes
20
Oh - and how are your RCA to XLR connected. You might get an improvement if you use the method of connecting the RCA screen both to the XLR Screen wire AND the XLR cold wire (via a resistior matching the output impedance of the receiver) at the reciever end, and not connect the cold pin to screen at the amp end. So running 3 connections - so called pseudo balanced as shown in the pictures here:


I actually don't know which of the two I'm using, I bought this RCA to XLR cable from Amazon.
 
OP
J

jd_cincy

Member
Joined
Feb 2, 2022
Messages
22
Likes
20
This is almost certainly ground loop noise. PC's are terrible for generating this. When your PC is electrically isolated (connected only by Toslink) then there is no problem. As soon as you make an electrical connection (HDMI) then you have a loop from the PC earth through the reciever, and via your RCA to XLR cables, to the VTV amp, and back to earth through it's power connection. Then you have a powerful desktop PC with GPU generating all sorts of stray magnetic fields that couple into the ground loop and cause the noise. The noise is actually being injected in the unbalanced connection between the receiver and the amp.

The good news this is not a fault in any of the kit. The bad is that it's not that easy to solve without a balanced connection available between receiver and amp.

Suggestions to try to improve:
Plug PC, receiver and amp into the same socket, or power strip.
Connections between receiver and amp to be made as short as possible. You might need to build the interconnect yourself for that - only as long as absolutely needed.

Then minimise the area of the loop. Rec-amp interconnect routed close to amp power. Amp power to be run close to pc power back to the socket.

But ALL other PC cables (especially monitor graphics) to be separated from all audio kit as much as possible. Your problem here is the audio HDMI lead. It is part of the ground loop, but plugged into the worst case PC component for noise.



By the way - you can check this theory if you have or can borrow a laptop with HDMI out. Use that on battery as a source instead of your PC - my guess is that will not have any ground loop/noise problems - because it has no connection to earth.
Thank you for all of this information. I did confirm there is no noise using the same HDMI cable to connect a laptop on battery power, so it seems it is a ground loop.

The receiver, amp and pc all plugged into the same UPS device, which I thought would help minimize ground loop issues. I also moved all the plugs to the battery side of the UPS yesterday to test to see if maybe the battery and surge-only sides of the UPS would make a difference (it didn't).

In practice, it would be difficult to separate many of the cables due to the way my office is organized. I have a sit / stand desk and all the cables to the speakers and monitors, keyboard, and mouse are bundled together.

The receiver itself is only a 2 prong connector. Would using the "Signal Ground" connection on the back help? If so, what would I ground that to?

1649594940949.png
 

tonycollinet

Major Contributor
Joined
Sep 4, 2021
Messages
3,036
Likes
4,573
Location
UK/Cheshire
All those cables bundled together is (especially the graphics related ones) is real problem for ground loop. I'm not surprised you are having a problem in that arrangement, and doubt you will solve the problem with it that way.

If you run a thick wire from that ground stud back to the case of the PC (anywhere you can connect to the PC Ground), you might make an improvement by giving a return path for the loop other than the one through your RCA/XLR connectors. Worth a try, though I doubt it will eliminate the noise completely. You could also do that in combination with installing some clip on ferrites over the RCA/XLR connections - but again this will only reduce rather than eliminate.

The only other thing you could do which shoudl give a good improvment would be to get an active RCA to XLR converter, and send true balanced to the amp, but that would have to be located very close to the amp with the shortest possible RCA connector between it and the amp.
 
OP
J

jd_cincy

Member
Joined
Feb 2, 2022
Messages
22
Likes
20
Thanks for all the responses on this topic. Tried a bunch of things, but I'm giving up until I have an opportunity to recable everything top try to isolate the PC cables from audio. It would be nice to have all 5 channels uncompressed while gaming, but 2-channel is the most important, so I can live with it for now.
 
Top Bottom