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Ultimate HDMI Cable Noise Test
Hello,
In this HDMI cable noise test the following was done: PC connected to power box. Monitor connected to same power box. Receiver connected to same power box. Powerbox connected to wall socket (no earth grounding/wire) PC - VGA cable - Monitor PC - USB cable - Keyboard PC - USB cable - Mouse PC - HDMI cable - Receiver Receiver - analog cables - Speakers Everything else disconnected. The test was recorded on video/audio and placed on youtube: HDMI cable noise test video: https://youtu.be/bZSdQcPWKkg During this test a very clear NOISE signal can be heard coming from the HDMI cable when the PC is ON. When the PC is OFF and/or disconnected there is no NOISE signal. I think this video is very clear evidence that there is some kind of NOISE signal being transmitted across this HDMI cable. Perhaps friday I may repeat this test with a high quality/expensive HDMI cable to see if it makes any difference. (If the other person agrees to provide this cable). What is the source and why is there noise ? I think it might be the excessive voltage/power being dumped on the chasis by the PC's power supply since it's not grounded and entering the HDMI cable connectors/plugs. Let me know your thoughts, do you still believe it's a ground loop ? Do you still believe HDMI cables are not capable of transmitting noise ? Also an analog cable noise test was done as well, different kind of humming noise, but also coming from PC. Analog cable noise test video: https://youtu.be/cvpEWoxGj_s One question could be: Why is the humming different for analog ? My hunch is it's the receiver's analog inputs, it's being noise-filtered or so, but apperently it does not do the same for HDMI. Perhaps an oversight in the DENON manufacturer's design, believing HDMI does not transmit noise, just speculation though, it could also be the Creative X-Fi Elite Pro 7.1 soundblaster filtering out these signals before transmission over analog cables. Bye, Skybuck. |
#3
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Ultimate HDMI Cable Noise Test
On Wednesday, December 19, 2018 at 11:27:25 PM UTC+1, Paul wrote:
wrote: Hello, In this HDMI cable noise test the following was done: PC connected to power box. Monitor connected to same power box. Receiver connected to same power box. Powerbox connected to wall socket (no earth grounding/wire) PC - VGA cable - Monitor PC - USB cable - Keyboard PC - USB cable - Mouse PC - HDMI cable - Receiver Receiver - analog cables - Speakers Everything else disconnected. The test was recorded on video/audio and placed on youtube: HDMI cable noise test video: https://youtu.be/bZSdQcPWKkg During this test a very clear NOISE signal can be heard coming from the HDMI cable when the PC is ON. When the PC is OFF and/or disconnected there is no NOISE signal. I think this video is very clear evidence that there is some kind of NOISE signal being transmitted across this HDMI cable. Perhaps friday I may repeat this test with a high quality/expensive HDMI cable to see if it makes any difference. (If the other person agrees to provide this cable). What is the source and why is there noise ? Hum comes from analog ground loops. Occasionally hum comes from a failure in the power rectification and filtering section. (In the past, many AV receivers did not regulate V+ and V- on the power amp section.) Sometimes the ground loop is part of the design of the AV, and there's nothing you can do to fix it. Sometimes, the AV is influenced by crappy house wiring. And sometimes, leaving your analog 1/8" plugs connected at the same time as you plug in an HDMI cable, causes the problem. When testing HDMI, the *only* input cable to the AV should be the HDMI cable, while you test for noise. If there is still hum, it suggests the AV receiver is not floating and has a hard reference to ground. And the ferrite lumps on the HDMI cable, do not filter AC noise. The ferrite works at 10MHz-30MHz for example, filtering RF from the computer. The ferrite does nothing at 50Hz or 60Hz. I have a hard enough time removing ground loops from my own stuff here, so I'm not the best person to advise on this. Paul Somebody (on another newsgroup) mentioned "pin 1 problem" googling this reveals some info about that. Try googling "the pin 1 problem". Let me know what you think of this pin 1 shielding/earthing (?) problem. Bye, Skybuck. |
#4
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Ultimate HDMI Cable Noise Test
wrote:
On Wednesday, December 19, 2018 at 11:27:25 PM UTC+1, Paul wrote: wrote: Hello, In this HDMI cable noise test the following was done: PC connected to power box. Monitor connected to same power box. Receiver connected to same power box. Powerbox connected to wall socket (no earth grounding/wire) PC - VGA cable - Monitor PC - USB cable - Keyboard PC - USB cable - Mouse PC - HDMI cable - Receiver Receiver - analog cables - Speakers Everything else disconnected. The test was recorded on video/audio and placed on youtube: HDMI cable noise test video: https://youtu.be/bZSdQcPWKkg During this test a very clear NOISE signal can be heard coming from the HDMI cable when the PC is ON. When the PC is OFF and/or disconnected there is no NOISE signal. I think this video is very clear evidence that there is some kind of NOISE signal being transmitted across this HDMI cable. Perhaps friday I may repeat this test with a high quality/expensive HDMI cable to see if it makes any difference. (If the other person agrees to provide this cable). What is the source and why is there noise ? Hum comes from analog ground loops. Occasionally hum comes from a failure in the power rectification and filtering section. (In the past, many AV receivers did not regulate V+ and V- on the power amp section.) Sometimes the ground loop is part of the design of the AV, and there's nothing you can do to fix it. Sometimes, the AV is influenced by crappy house wiring. And sometimes, leaving your analog 1/8" plugs connected at the same time as you plug in an HDMI cable, causes the problem. When testing HDMI, the *only* input cable to the AV should be the HDMI cable, while you test for noise. If there is still hum, it suggests the AV receiver is not floating and has a hard reference to ground. And the ferrite lumps on the HDMI cable, do not filter AC noise. The ferrite works at 10MHz-30MHz for example, filtering RF from the computer. The ferrite does nothing at 50Hz or 60Hz. I have a hard enough time removing ground loops from my own stuff here, so I'm not the best person to advise on this. Paul Somebody (on another newsgroup) mentioned "pin 1 problem" googling this reveals some info about that. Try googling "the pin 1 problem". Let me know what you think of this pin 1 shielding/earthing (?) problem. Bye, Skybuck. That's an analog interconnect concern. The HDMI cable is pure digital. There's a difference. For HDMI, the high speed lanes are differential, and the receiver subtracts D+ and D- to develop a data bit from it. Any signals impinging common mode on both D+ and D- at the same time, are rejected. And this can happen, up to the common mode input limit of the technology. You can still upset a technology like that, but it takes more effort. Ethernet is also differential. But Ethernet is *unshielded* and what do you notice ? It works. It works reliably. It uses transformers to reject common mode signals. If you hang a scope off the floating wires, the noise amplitude is *huge*, but the fake noise as it were, is stopped in its tracks by the common mode rejection of the transformer. It's one of the single nicest inventions in electronics, as far as I'm concerned. Your XLR microphone problem, the signal is analog and a microphone may have lower amplitude signals involved. There are a number of different microphone types, and each has a characteristic voltage range. For example, my one good microphone here, is an electret, followed by a chip amp (not an opamp) inside the microphone. The result is a line level (1 volt AC) signal is presented, and that microphone properly belongs plugged into Line-In instead of Microphone-In. I have other crappy microphones without that here, and there's no comparison on quality. You can actually hear sounds in the room with the Line Level microphone. It's much more sensitive, and any noise currents (S/N) are much smaller compared to the signal. An AV receiver can have a ton of stuff wired to it, and it's possible some other wiring is compromising your S/N ratio. Check whether you're running 7.1 analog 1/8" wiring *at the same time* as the HDMI cable. Paul |
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