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TOPIC: Audio Distortion

Audio Distortion 2 years 8 months ago #13481

  • chaleboy
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I am using the AVR 8x8 with my Arcam AV888 preamp to affect EQ in my home theater. Very frequently, there is very loud distortion rather than normal audio when starting to play audio. I can sometimes but not consistently correct it by changing audio sources. Other times there are is no audio.. I am updated to the latest firmware that shipped with the device. Any advise appreciated.
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Audio Distortion 2 years 8 months ago #13484

  • Jim the Oldbie
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Hello,

I don't own a nanoAVR (yet), but I'm wondering if you've set your source (blu-ray/dvd player, PC, whatever) to output linear PCM audio only (no bitstreaming) via HDMI?

-- Jim
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Audio Distortion 2 years 8 months ago #13485

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Thanks Jim,

I will check however my setup makes this a bit more complicated.

I am running distributed audio and video with a control 4 HDMI matrix. For the main tv, the hdmi matrix output goes into the nanoAVR which in turn outputs via HDMI to the input of my Arcam preamp where I need the audio adjustments. The problem is the sources that I use, directv, Apple TV, DVD, I use in more than one zone. If I switch to linear PCM audio only, for the sources, will the other non surround areas be able to decode that for normal stereo? I am not that familiar with PCM.

Thanks for your thoughts,
Charles
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Audio Distortion 2 years 8 months ago #13486

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I guess my other question would be why would this device only support linear PCM audio and not bit streaming?
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Audio Distortion 2 years 8 months ago #13489

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chaleboy wrote:
...If I switch to linear PCM audio only, for the sources, will the other non surround areas be able to decode that for normal stereo? I am not that familiar with PCM.

My guess is that most all downstream stuff should be able to handle LPCM, and downmix if necessary; in fact I think it may be required, but that's only a guess. Perhaps someone else here can verify this.

But before we get ahead of it, it should be noted that if switching to LPCM reliably fixes the nasty noise problem, this is not really a complete solution. If you can reliably repeat the symptoms with bitstream sources, this would indicate abnormal operation by the nanoAVR, which should be absolutely muting any & all bitstreams since it can't decode them. Let us know what you find.

chaleboy wrote:
I guess my other question would be why would this device only support linear PCM audio and not bit streaming?

I thought this was discussed in another thread around here somewhere, but I sure can't find it now. I think it has to do with maintaining a reasonable price point. Dolby/DTS (bitstream) decoding would not only make the hardware more complex, it would also require payment of licensing fees to those companies. All of which would probably have increased the price of the unit considerably. I would speculate that the design objective of nanoAVR was to provide a little box of useful features that are not readily available in the majority of AVR solutions, while leaving out the stuff that our other gear can (hopefully) already do.

-- Jim
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Audio Distortion 2 years 8 months ago #13493

  • john.reekie
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I suspect Jim is right on with the licensing. miniDSP will already have the burden of the HDMI licensing - www.hdmi.org/manufacturer/terms.aspx
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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Audio Distortion 2 years 8 months ago #13540

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This is the companies response:

"Mmmh, this is very odd based on the fact that we’ve never heard of this before. Our guess at this time is that you’re maybe feeding an encoded signal to that unit (e.g. Dolby/DTS). As per the user manual, you should always feed a PCM source.i.e. decoding must be done in your source. You can see the user manual for more info and feel free to let us know if any questions."

My issue is that I need to use the EQ adjustments for a particular room for all audio sources e.g., blue ray player, satellite TV, etc. My understanding it is very common to have linear PCM for blue ray and high quality audio sources as an output option but not for satellite. I went through my new high end satellite box [directv hd-44] and they do not have a choice for linear PCM output. So what is the purpose of using this box for room audio correction if I can't use it for all my audio sources? How can I get by this issue?
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Audio Distortion 2 years 8 months ago #13542

  • Jim the Oldbie
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chaleboy wrote:
This is the companies response:

"Mmmh, this is very odd based on the fact that we’ve never heard of this before. Our guess at this time is that you’re maybe feeding an encoded signal to that unit (e.g. Dolby/DTS). As per the user manual, you should always feed a PCM source.i.e. decoding must be done in your source. You can see the user manual for more info and feel free to let us know if any questions."

I hope for their sake that devteam spend a bit of time checking this out. If certain bitstreams are able to fool the nanoAVR into thinking they are normal LPCM so that it passes them through (as a loud noise), this could lead to more damaged speakers and unhappy customers. If it's not too much trouble, perhaps you could provide them with some details as to which source, movie, etc. causes this problem so that they might be able to reproduce it & find a way to keep it from happening? Of course this still doesn't solve your problem below, unfortunately:

chaleboy wrote:
...I went through my new high end satellite box [directv hd-44] and they do not have a choice for linear PCM output. So what is the purpose of using this box for room audio correction if I can't use it for all my audio sources? How can I get by this issue?

I'm afraid there's no way around the fact that nanoAVR can't work with bitstream audio. The only possible solution I can think of (and granted, it's a bit of a long shot) is this: The current Oppo BD players (BDP-103 & 105) have HDMI inputs as well as outputs. They are also capable of LCPM output via HDMI. If they have the ability to decode a bitstream on the HDMI input, then ouput that as LCPM on the HDMI output, (and if you didn't mind throwing more money at the problem :angry:), you could connect your sat box to the HDMI input on one of these units. I looked through the BDP-103 manual on the site and could not find a specific reference to this particular scenario. But there are a lot of Oppo owners out there (even here maybe?). Hopefully someone in one of these forums can verify whether the above is possible.

Good luck,

-- Jim

P.S. Devteam if you read this: The no-bitstream rule is an understandable limitation for this product, and something many of us are (or will be) able to work around. But it's also a pretty important point for all potential buyers to understand fully - especially when combined with an "all sales final" policy. As it reads now, the no-bitstream rule is only implied on the nanoAVR product description page in the sentence, "...unmatched level of tuning of eight channels of uncompressed audio (raw/PCM)." Perhaps it would be wise to consider spelling it out a bit more explicitly there? It might help to prevent more unfortunate situations such as the one in which Charles now finds himself. Just a suggestion...
Last Edit: 2 years 8 months ago by Jim the Oldbie.
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Audio Distortion 2 years 8 months ago #13581

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Jim the O--

Thank you for your comments. In further research, this is indeed the case. Audio feeds of bitstream sound are coming through as loud noise [and why is this being allowed to happen?]. When I purchased the nanoAVR, I did not see any comment on the no bitstream rule and only after can only find subtle explanations of this in documentation, that you need to feed PCM audio and absolutely NO comment that it cannot take bitstream audio e.g., dolby digital, etc. This is really a bummer. I have an Oppo 103 and had also considered that as an option as feeding audio through it as a loop, but seems like a headache and already have significant time investment to just get to this point figuring out what is going on. I need a breather to decide where I want to go from here.
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Audio Distortion 2 years 8 months ago #13603

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The following is another example of linear PCM not being sufficient. I have an Apple TV. If I play back a movie purchase that has Dolby Digital on it, there is no audio and only distortion as I discussed. The problem is that if I play back with Dolby Digital turned off on the Apple TV, there is only 2 channel stereo.

Future buyers beware, this unit is essentially ONLY good for use with blue ray/DVD players and cannot be used for EQ in most other situations.
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Audio Distortion 2 years 8 months ago #13616

  • john.reekie
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Did you try feeding the Apple TV through your Oppo? I've read that it works (DD in PCM out) but haven't gotten around to trying it myself yet (have to find the ATV and set it up as I don't normally use it)
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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