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TOPIC: Surround receiver before nanoAVR

Surround receiver before nanoAVR 7 months 1 week ago #36728

  • KimT
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Hi,
I will try to keep this simple:

1) Can a surround receiver be used as a HDMI surround processor?
I.e. the surround receiver will do decoding, HDMI (auto) switching, Dolby Pro logic, volume control, trigger signaling. It will pass a HDMI PCM 7.1 audio signal on to the next HDMI device in the chain, which could be another surround receiver, a nanoAVR HDA+PA, or a nanoAVR HD+a surround receiver.
It think it should work but I am worried about if the HDMI audio output from the surround receiver is 24 bit PCM 7.1 audio (or limited to 2.0) and if the volume control has been applied digitally or not. If the volume control has been applied digitally, the output should of course be 24 bit.

2) If it is possible, I am considering using a nanoAVR for bass management and digital XO for the front speakers in a 5.2 setup I have. See the illustration I have made. I prefer using a HDMI splitter instead of sending the HDMI signal through the nanoAVR to the TV. However, the HDMI splitter will have to allow me to overrule standard behavior and make the output 7.1, even if the TV requests 2.0. HDAnywhere has a HDMI splitter that can do that.
What challenges/problems do you see with this setup?

Best regards,
Kim
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Surround receiver before nanoAVR 7 months 1 week ago #36733

  • john.reekie
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I've never tried anything like that, but I would think the answer to your question really depends on what the receiver sends out its HDMI output. I wouldn't just assume that it's a decoded LPCM signal... does the receiver's user manual have anything to say about it?
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
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Surround receiver before nanoAVR 7 months 1 week ago #36735

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Hi John,

If I understand the HDMI standard correctly, the surround receiver would negotiate the audio format with the nanoAVR (actually the HDMI splitter but lets forget about that for now). The nanoAVR would say it supports 8 audio channels but only LPCM. Then the surround receiver would send the 8 decoded audio streams to the nanoAVR. Similarly, if you connect a surround receiver to a TV, the TV would say that it only supports LPCM 2 channels and the surround receiver would downmix the signal for the TV to LPCM 2 channels.
Now, is this really part of the HDMI specifications and is it something I can always rely on (no matter what surround receiver I buy)?

I have a custom in-wall and attic installation, and I am looking for a generic solution that does not put any constraints on what surround receiver/preprocessor is used. I mention a surround receiver instead of a HDMI pre processor because of the normally huge price difference. Since there should be no D/A conversion, the quality of the surround receiver is not so critical. The idea is to install some good quality power amplifiers and DSP boards for long term use and then make it possible to change the surround receiver/processor when new audio/video formats etc. show up without having to spend a fortune to get decent audio quality.

Background:
I have had the custom installation for 8-9 years and so far been using a Denon 4306 surround receiver and passive crossovers. The crossovers are installed in the attic above the listening/living room and I have always wanted to upgrade the system with digital crossovers. I also have two 2xib15 subwoofers going into the attic, which is a nice dry room with almost constant temperature. I want to decouple as much as possible of the audio system and place it in the attic. Ideally, only a single HDMI (or other digital audio) wall-outlet should be located in the living room, to distribute the audio signal to the attic. Today I have a patch panel with a bunch of speakon and neutrik connectors.
Besides simplicity, I also care a lot about user-friendliness. Today a custom made remote control turns on all the right stuff but it would be nice with a more bullet proof/standard solution perhaps using HDMI CEC (if possible).

/Kim
Last Edit: 7 months 1 week ago by KimT.
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Surround receiver before nanoAVR 7 months 1 week ago #36737

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The nanoAVR will only decode LPCM, of up to 8 channels, and AFAIK only up to HDMI 1.4.... The sending device will need to conform to that, or it won't work...
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
Last Edit: 7 months 1 week ago by john.reekie.
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Surround receiver before nanoAVR 7 months 1 week ago #36742

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Thanks John, it is a good point. It is not only the number of audio channels I have to worry about.

I assume that the surround receiver would "fall back" to HDMI 1.4 (or lowest standard supported by the TV and the nanoAVR) in that case.
Similarly, if you put the nanoAVR between the sources and the TV, like suggested in the minidsp user guide, I think you will eventually run into problems because the nanoAVR is limited to HDMI 1.4. Then you will have to buy a new nanoAVR/replacement product to get the latest video formats etc. However, on the audio side there is no reason to upgrade as 24 bit, 192 kHz sample rate and 8 channels, which has always been part of the HDMI spec., is more than enough for a 5.x/7.x system and I have no plans to install speakers in my ceiling for Dolby Atmos etc.

Maybe the solution can be found in a suitable (intelligent) HDMI splitter, that can "downgrade" the HDMI signal to HDMI 1.4 to the nanoAVR and pass HDMI 2.0/x.y on to the TV.
Last Edit: 7 months 1 week ago by KimT.
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Surround receiver before nanoAVR 7 months 5 days ago #36801

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Please correct me if I am wrong.

I have come to the conclusion that HDMI is (probably deliberately) designed in a way that makes it impossible to avoid hardware upgrades/replacement related to audio as new HDMI versions arrive. It is primarily because audio and video cannot/is not meant be separated. So even though I would be satisfied with HDMI 1.2 audio I have to upgrade my equipment if I want HDMI 2.1 picture.
If I should provide backwards compatibility to nanoAVR HDMI 1.4 but still get HDMI 2.1 to the TV, it seems it would require a special surround processor with two independent HDMI outputs or a special HDMI splitter with re-encoding capability. Also, the nanoavr only supports LPCM data. Either way this special device would have to support outputting two different HDMI versions at a time (which might require realtime re-encoding and/or a dedicated audio out HDMI like the Oppo). In some cases, a HDMI splitter with EDID processor might be sufficient but not in general. And when I get a new TV which could benefit from an even never HDMI standard, I would also have to upgrade the special HDMI processor and there is no guarantee that such a product will be available for the new HDMI standard.

Besides Oppo, I have found a few products that might work but the audio decoding for the nanoavr will probably cause problems:
www.hdfury.com/product/avr-key/
www.amazon.com/dp/B0755TB82Q?tag=vs-avsforum-convert-20
I think in most products HDMI negotiation will cause the source to lower its output signal to HDMI 1.4 just be because one of the HDMI outputs are connected to a 1.4 device. Doing EDID processing probably will not work as the nanoAVR would not know what to do with a HDMI 2.1 signal and there is also HDCP and decoding to worry about.

It is much simpler with the old SPDIF interface. Unfortunately, only 2.0 and 5.1 AC3/DTS has been standarized for SPDIF even though it would be able to carry 8 channels 24bit 48 kHz audio data. It is a shame, as now us DIY people have to struggle with Dolby and DTS about licenses to decode AC3/DTS which also has a reduced sound quality.

As I only have a 5.2 system and because of all the HDMI problems, I think I will step away from HDMI for audio. Instead, I will buy a new TV (my old 52" TV is 9 years old) that is capable of re-encoding multichannel audio to AC3 or DTS on the SPDIF output. I will then connect my HDMI sources directly to the TV. The SPDIF out from the TV will contain LPCM, AC3 or DTS data. Just like when connecting a Sonos Soundbar.
For LPCM the case is simple but I need to get the AC3 and DTS signals decoded. Unfortunately, none of the minidsp products support this. I do not understand why, as there are lots of SPDIF->5.1 analogue out products on the market which apparently do not have licensing issues.
I have an ADI DSP board that can handle SPDIF input and analogue inputs but maybe i can also use minidsp 8x8 kit+digi fp but the plugin does not support FIR filters. My plan is to use the SPDIF input for music only (Sonos Connect) and six of the analogue inputs for surround. I.e. for the TV output I will buy a SPDIF->5.1 analogue out converter. That way the music signal will not be degraded but the TV signal will. I just have to accept that. Maybe it will be possible to modify the SPDIF->5.1 converter to output I2S and connect these to the I2S inputs on the DSP board but that is a project in itself. Let me know if anyone has experience with this :-)

Some of the SPDIF->5.1 converters have the advantage that they auto detect PCM/AC3/DTS and it is possible to make them mix PCM L+R to create a center channel. So far I have not found a product that uses Dolby Prologic but perhaps it is out there. I think it is important that some vocal always comes out the center channel when watching TV even if the signal is only 2.0.

On the DSP board I will probably do some auto detection of signals and choose between SPDIF music and the analogue TV signal that way. Similarly I have to implement a trigger signal to turn on all the power amplifiers.

The music signal volume is controlled from the Sonos app but I have to find a good way of handling volume control of the TV audio signal. It seems that I cannot control the digital output volume from the TV. It should be possible as TVs re-encode to AC3/DTS but of course there will also be a quality loss there. Do you know of any TVs that let you control digital output volume?

Alternatively, I have to install a small infrared receiver (if the TV uses a infrared remote, some uses Bluetooth) that can receive the remote control volume signals, like the Sonos Soundbar does. Or I could buy a SPDIF->5.1 analogue out converter with built in volume control and a remote control. But two remote controls will degrade the user friendliness. Btw. the boxes are not in the same room as the TV.
Any suggestions?

As a side note, it would have been nice if i could find a TV that had 5.1 analogue output. The Samsung TVs have the connect-one box but apparently not a version of it with 5.1 analogue output.

/Kim
Last Edit: 7 months 5 days ago by KimT.
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Surround receiver before nanoAVR 7 months 4 days ago #36811

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I have found a list of TVs with 5.1 output on SPDIF:
www.rtings.com/tv/tests/inputs/5-1-surround-audio-passthrough
However, it is not clear which of the TVs actually are doing re-encoding. I have read that at least LG should do DTS re-encoding in some of their models. If would be great if they would support DTS 96/24 output, then it would not be a problem to turn down volume digitally in the source (TV).

I have been reading a little bit about eARC and that might be a solution in the future, if I understand it correctly. I think it should be possible to connect HDMI 2.X devices to the TV and for instance a HDMI 2.1 surround receiver to the eARC HDMI port on the TV. The TV should then only send the audio to the surround receiver and it should not degrade the image quality to HDMI 2.1. The problem is that both the TV and the receiver will have to support eARC which means they should both support HDMI 2.1 or higher. So it will take some years before we can benefit from the backwards-compatibility, when HDMI 2.2 and so on becomes the new standard.
Can anyone confirm this understanding?
Last Edit: 7 months 4 days ago by KimT.
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Surround receiver before nanoAVR 7 months 4 days ago #36813

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I can't answer any of your questions about eARC etc but have you considered using analog input to a digital crossover? People using the DDRC-88A do so and have their receiver do all the decoding and switching. It sounds like in your case you could just use a 2x4 HD for the fronts.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
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Surround receiver before nanoAVR 6 months 4 weeks ago #36875

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I have considered different analog/digital solutions but there always seems to be a catch regarding user friendliness, audio quality or upgradeability. I am fine with analog inputs for surround and stereo content from movies/TV/games but I do not want analog input for stereo music reproduction. So either all inputs to the audio DSP should be digital or at least the input for music should be digital. Depending on the quality of the gear, it might not make an audible difference if there is and extra D/A + A/D step but one of the things I wanted to achieve was that it should not be necessary to buy an expensive preamp. I wanted to keep everything digital until reaching the PA. If I am going to pay more than a thousand dollars for a DSP (miniDSP products are quite expensive in Europe), I want a DSP that can manage a complete solution, i.e. bass management, crossovers and room EQ.

All my loudspeakers are bass limited, so the fronts also need the subs for music reproduction. I think it is a mess if the surround receiver should do the bass management. Ideally, I want to control bass management, delays, crossovers and room correction myself in a DSP. I have the skills to do the DSP code but I need some suitable hardware.

I have also thought about splitting it into two separate systems, a digital crossover+PA for music and just the surround receiver+old passive crossovers for surround. Then a relay system should switch which is connected to the loudspeaker drivers. One of several problems with this solution is that I would also have to maintain/setup the two systems separately and with two different room eqs (my own for music and the one integrated in the receiver for surround).

Maybe HDMI EARC and a new version of nanoAVR HDA supporting EARC will be a killer combination in the future. For now, it seems that the SPDIF output from the TV is the most bullet proof way and a cheap way to go without compromising sound quality for stereo music playback. However, it will downgrade the surround sound experience a little but I like the simplicity in the single SPDIF coax cable going from my TV to the hidden surround system. It is also easy to get and old high-end surround processor for decoding the AC3/DTS signal. If I make some auto turn on/off functionality and the TV has an IR remote (so that I can pass the volume up/down signals to the preamp), it might be possible to make it as user friendly as HDMI EARC.

Also, I have to consider that my current solution with a surround receiver and passive crossovers is relatively simple and working. It could be more user friendly but some (like my wife ;-) ) might say "If it ain't broke, don't fix it". I could buy a new surround receiver (and TV) to support latest video signals and improve user friendliness (if ARC and CEC is working) and it might even contain Dirac Live room correction but then I am still not much closer to realizing my digital-only signal path and digital crossover plans.
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Surround receiver before nanoAVR 6 months 4 weeks ago #36876

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There is that. I've learned (again and again and again... :whistle: ) that one should never dismantle a working system until the replacement is built and working...
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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