Reality Check: HDMI voltages

BaduFamily

BaduFamily

Active Member
HI crew.
 
I've just finished chatting with a service rep from Denon about a new issue in our AVR. The issue is that we've been getting frame drops, and sometimes multi minute video cut-outs, in our video. Audio is fine.
 
The service rep is telling me that this is probably due to a voltage drop in long cables; that the AVR isn't able to put out enough voltage - infact that the voltage in the HDMI signal starts at the source device and degrades all allong the way.
 
this makes no sense to me at all.
 
our signal path is
 
VHS deck
Tivo
Apple TV     all into ------> Denon ---> Oppo ----> Epson Projector
Oppo
 
which produes flickering dropoy from all sources.
 
any of the HDMI sources directly into the Oppo and then to the projector are fine. this rules out voltage drop on the long cable run.
 
going from the Denon straight to the projector produces drop outs.
 
The cables between the source devices and the oppo are about 1 meter in length.
 
so my reality check question is this: my mental model has the digital signal re-formed at each stage. re-formed isn't really the right word, but at least brought up to proper voltages.  <<<--- is this the wrong model?
 
Odd behaviors -
a) if I display the denon setup menu overlaid on the signal we get no drop outs. the rep said that this is because the menu is 480 and uses less voltage. I mentioned that the menu is overlaid the original content so it's not actually 480 but she disagreed.
 
b) as a test I ran the AVR all night showing late night whatever. in the morning I was able to watch the first ball game yesterday with no drop out. Measuring the temp of the denon's back panel showed a nice 85 degree operating temp, so I'm now wondering if there isn't some mechanical problem with the connectors themselves - which is resolved as the box gets hot and everything expands.
 
footnote: the oppo is at the end of the chain for upscaling / darby
 
 
 
 
 
 
Long cables?
 
Cripes 50' HDMI cables are commonly sold most places.
One of the reasons this stuff went digital is the eliminate the degradation of analogue signals from cable capacitance absorbing and phase shifting signals.. With a few metres of cable this should never be a problem.
 
Did you try swapping some other cables in as a basic troubleshooting technique?
 
The Denon AVR and the Oppo BDP are 2 different devices, with different HDMI cards. Don't expect them to treat the same HDMI cable the same.

HDMI sucks.

Try HDMI pass through, on the AVR. Any trouble with dropouts when the AVR doesn't alter the video?

JDSmoothie and BatPig, and everyone else at AVS, say to leave any video conversion to the TV, that TVs have superior scaling to all AVRs. I think you'll lose the volume overlay, but it may solve your problem.

Ask at AVS in your AVR thread - which model?

Not all HDMI cables are made alike. What gauge are you using? A thin 'super slim' may not be the best option for a longer run. You could also consider a directional powered Redmere.

I have a 40 foot run to install. I'm leaning toward a Blue Jeans' thicker cable (can't recall the name), from my x3200w to the TV.
 
My old Denon 3808 had video dropouts -handshake issues - which were solved by installing a Monoprice splitter in the chain. Not sure why it solved the problem, but someone stumbled on the fix, and it worked for many people with the same issue, with that Denon model, at the time. No, I doubt it would solve your issue. IIRC, it has been explained as a 'clock issue', with HDMI. HDMI sucks.
 
Thanks all, catching up ( it's a beautiful day in Norcal and I've been out on the stumpy riding about ) 
 
- stress relief yes. these connectors are always a PITA in this reguard. what I had done is to use velcro to hang any overage in length so the plugs go straight in. They're at 90 degrees to the back of the AVR case. This setup has been in place for over a year, as when I hooked all the thick cables up I realized they were going to be under stress. next time I'll look for a AVR with some kind of screw-in options for those HDMI cables with the mounting screws.
 
cable length in question: 3' max interconnect. 25' redmere to projector. 
 
interconnect cables have been swapped a number of times as part of diagnosis. Removing AVR from mix eliminates dropouts.
 
The AVR isn't doing any scaling/ processing. it's passing through the source signals. The end of the chain is an Epson projector on AVR monitor 1 and a small LCD display on monito 2 in the mechanical room. Neither of those are doing any rescaling. ( yes we get drop outs when only using one monitor out, on either monitor out, both in 'auto select' mode and when each monitor out is explicitly set. )
 
Cables: stout momoprice cables, no-name thick cables from a computer equipment supply store, and locking ACCELL cables from Amazon. Have a 3' Blue Jean cable on order.
 
The OPPO is doing some image processing. however the test configurations of oppo as source straight to projector and of of oppo as intermediary between other sources and the projector are fine.
 
yes have been through AVS thread; that's where I leared about the 'reset the microprocessor' trick-of-last-resort. I may return with the bewlidering Denon chat log tho.
 
what I am curious about is the Denon rep's insistance that the voltage in a chain of HDMI devices 'starts' at a given level at the source device and only the source device provides that voltage level. Also the rep's instance that higher resolutions use higher voltages to drive the signal through all the devices in the chain.
 
Given that the HDMI sink ( the thing at the end of the chain ) and all the bits along the chain are decrypting and recrypting the signal I can't see how the Denon rep's comments makes any sense. The AVR is still in warranty but with discussions like I allude to above I'm not sure I can get a RMA out of them.
 
Try the long run with a non-Redmere. I have read that they can be problematic.

Dumb question, don't want to rule anything out, but you sure the directional Redmere isn't backwards? Easy mistake, I've read of many people doing that. Common problem.

Isn't the long run to the PJ the obvious problem? I doubt any 3' HDMI would cause any issues, regardless of construction.

Remove the small monitor at the rack. Take it out of the chain until your troubleshooting is done. HDMI will scale to the lowest resolutuon of connected displays.
 
Neurorad said:
HDMI will scale to the lowest resolutuon of connected displays.
Click to expand...
 
After many years and failed attempts to get HDMI or EDID problems sorted out I've found it would almost always have been cheaper (from the standpoint of expensive gizmos and wasted time) to toss out the gear that wouldn't play nice and replace it with something that does.  Especially when trying to play double-duty with sending outputs to devices with different features.  Just... stop... it won't ever work right.  Yeah, there's always a few success stories, but I'm sick of chasing unicorns.
 
Thanks again all. I am pretty sure I pulled the redmere correctly.
This setup has been working quite well for 14 months.
I'll just double check tho.
would be a pita to pull another through the ceiling.
 
Bill your sage advice is inspiring. I can always move this amp to the garage workshop!
 
Honestly, I can't count the hours wasted on trying to make some of these AV gizmos come close to doing something fancier than their basic purpose.  Sooooo close, soooo many times.... but falling dead on the rocks of due to an unacceptably low WAF.  
 
Personally, I find it's better to just get (and keep) the incompatible crap out of the equation entirely.  Better to have it gather dust permanently rather than sneak it's way back into wasting MORE of my time later.  Don't fall prey to the sunk cost fallacy.
 
BaduFamily said:
Thanks all, catching up ( it's a beautiful day in Norcal and I've been out on the stumpy riding about ) 
 
- stress relief yes. these connectors are always a PITA in this reguard. what I had done is to use velcro to hang any overage in length so the plugs go straight in. They're at 90 degrees to the back of the AVR case. This setup has been in place for over a year, as when I hooked all the thick cables up I realized they were going to be under stress. next time I'll look for a AVR with some kind of screw-in options for those HDMI cables with the mounting screws.
 
cable length in question: 3' max interconnect. 25' redmere to projector. 
 
interconnect cables have been swapped a number of times as part of diagnosis. Removing AVR from mix eliminates dropouts.
 
The AVR isn't doing any scaling/ processing. it's passing through the source signals. The end of the chain is an Epson projector on AVR monitor 1 and a small LCD display on monito 2 in the mechanical room. Neither of those are doing any rescaling. ( yes we get drop outs when only using one monitor out, on either monitor out, both in 'auto select' mode and when each monitor out is explicitly set. )
 
Cables: stout momoprice cables, no-name thick cables from a computer equipment supply store, and locking ACCELL cables from Amazon. Have a 3' Blue Jean cable on order.
 
The OPPO is doing some image processing. however the test configurations of oppo as source straight to projector and of of oppo as intermediary between other sources and the projector are fine.
 
yes have been through AVS thread; that's where I leared about the 'reset the microprocessor' trick-of-last-resort. I may return with the bewlidering Denon chat log tho.
 
what I am curious about is the Denon rep's insistance that the voltage in a chain of HDMI devices 'starts' at a given level at the source device and only the source device provides that voltage level. Also the rep's instance that higher resolutions use higher voltages to drive the signal through all the devices in the chain.
 
Given that the HDMI sink ( the thing at the end of the chain ) and all the bits along the chain are decrypting and recrypting the signal I can't see how the Denon rep's comments makes any sense. The AVR is still in warranty but with discussions like I allude to above I'm not sure I can get a RMA out of them.
Click to expand...
 
The Denon rep doesn't know what they are talking about.  An HDMI link is a differential pair (essentially I2C).  Voltage is not the critical factor on the wire, although if it is too far out of spec, it can cause problems.  And voltage drop does not "accumulate" from one device to the next.  At each input, there is a receiver, and no matter what processing (or lack of processing in pass through mode) there is within the device, the HDMI signal is regenerated at the output.
 
And the fact that the overlay menu has no drop outs has nothing to do with voltage.  HDMI is a digital signal, so a 480p signal results in different data packets vs a 1080p signal.  It has no effect on voltage whatsoever.
 
Since everything works ok when connected to directly to the Oppo, that points to the Denon as the source of the trouble.  Sounds like you've eliminated the cables as a potential source of trouble by swapping them out.  More reason to think the Denon is the cause of the problem.  An since the overlay menu has no drop outs, that makes me think the problem is more towards the input side.
 
RAL said:
The Denon rep doesn't know what they are talking about.  An HDMI link is a differential pair (essentially I2C).  Voltage is not the critical factor on the wire, although if it is too far out of spec, it can cause problems.  And voltage drop does not "accumulate" from one device to the next.  At each input, there is a receiver, and no matter what processing (or lack of processing in pass through mode) there is within the device, the HDMI signal is regenerated at the output.
 
And the fact that the overlay menu has no drop outs has nothing to do with voltage.  HDMI is a digital signal, so a 480p signal results in different data packets vs a 1080p signal.  It has no effect on voltage whatsoever.
 
Since everything works ok when connected to directly to the Oppo, that points to the Denon as the source of the trouble.  Sounds like you've eliminated the cables as a potential source of trouble by swapping them out.  More reason to think the Denon is the cause of the problem.  An since the overlay menu has no drop outs, that makes me think the problem is more towards the input side.
Click to expand...
Agree with most of your points, especially the overall conclusion. A couple of the intermediate points are a little off though.
I2C is not differential, and is a slow speed command and control... maybe you were thinking LVDS?
Completely agree on all your voltage comments.
480p vs 1080p - this will actually cause the HDMI to run at two different clock speeds. One of the HDMI pairs sends just the clock signal. The others run the data. In order to send more data for a higher res screen, everything runs faster. So if you have a marginal system where the data eyes are closing or distorted, the higher res signal may fail where the lo-res works.
 
mdesmarais said:
Agree with most of your points, especially the overall conclusion. A couple of the intermediate points are a little off though.
I2C is not differential, and is a slow speed command and control... maybe you were thinking LVDS?
Completely agree on all your voltage comments.
480p vs 1080p - this will actually cause the HDMI to run at two different clock speeds. One of the HDMI pairs sends just the clock signal. The others run the data. In order to send more data for a higher res screen, everything runs faster. So if you have a marginal system where the data eyes are closing or distorted, the higher res signal may fail where the lo-res works.
Click to expand...
 
You're right.  Don't know what I was thinking when I wrote I2C. I also agree with your comments about the 480p vs 1080p speeds and the higher speeds possibly causing loss of signal quality.   The point I was trying to make was the the two speeds do no use different voltages as the Denon rep claimed. 
 
Since the set up menu is an overlay, I suspect it may be 480p resolution upscaled to match the 1080p signal it is overlaying.
 
RAL said:
You're right.  Don't know what I was thinking when I wrote I2C. I also agree with your comments about the 480p vs 1080p speeds and the higher speeds possibly causing loss of signal quality.   The point I was trying to make was the the two speeds do no use different voltages as the Denon rep claimed. 
 
Since the set up menu is an overlay, I suspect it may be 480p resolution upscaled to match the 1080p signal it is overlaying.
Click to expand...
Yup- if the video is visible behind the menu, then it has to be sending the full resolution over the HDMI.... that rep is really out to lunch. ;-)
 
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