Adding post-DSP SPDIF outputs to AVRs

[mdsimon2]

There shouldn't be any need to buffer the clocks; certainly not for an internally mounted board. They are already paralleled to multiple ICs and the inputs are high impedance.

Interesting, I wasn't using an AVR but rather a miniSHARC which seemed very sensitive to MCLK loading, good to hear you can just split 4 ways with an AVR.

Michael

 

[voodooless]

There are also various ADAT encoder ICs capable of taking all four I2S data channels.

Really? Which ones? I've been looking for these a bit, but can't really find anything useful. Would be nice to simply have an 8-channel ADAT output on your AVR. 8x 24bit/48kHz should be enough for most use cases since AVRs do most processing at that rate anyway. And you can just hack one more optical output into the AVR to make this possible.

Edit: finally found some. Coolaudio seems to have some encoder and decoder IC’s.

There may be a better alternative though. Why not just use an Xmos and convert immediately to USB?

 

[jamescarter1982]

Greetings!

I thought it might be fun to share details of a current project, which involves modifying AVRs with post-DSP SPDIF outputs. This effectively turns any AVR into a fully digital audio processor with room correction, subwoofer crossover/time alignment and EQ functionality.

The potential applications are numerous and I am in the process of producing a rather elaborate video that should enable anybody with moderate DIY electronics experience to perform this modification.

View attachment 106784

The modification itself is fairly straightforward and entails hijacking the front channel I2S output which runs between the unit's DSP and DAC. A readily available WM8804 board can then be used to obtain a stereo coaxial SPDIF output for those channels.

View attachment 106785

I expect to complete production of the video guide within a few weeks. These photos were taken during a quick test, to ensure that my script did not omit any relevant detail. The procedure is applicable to almost any AVR, with pin locations and channel pairings being the only significant variables.

View attachment 106786

This is a cheap, used Denon AVR-2807. It was manufactured in 2006 and was one of the first Denon units to include Audyssey MultiEQ.

The thought had also occurred to me that the AD IC would be fairly easy to control via I2C for arbitrary DSP. Perhaps I'll look into that soon!

I wondered recently if the dsp chip inside an avr could be somehow controlled by a pc to provide parametric eq or something similar by an ipad app or similar though have no idea if this is possible or even a good idea

 

[deadwood83]

Oooooh very clever! I took a peek at big M's website and found a photo of a current model (NR17111) which looks very receptive to this addon.

Not sure a manual is even needed with such detailed PCB markings.

And I have a gustard X20 sitting on a shelf doing nothing with that LVDS port on the back.....

 

[harlizzle]

I would really love to do this to my receiver. Where would I even start to look to find someone capable of doing this?

 

[Weeb Labs]

I would really love to do this to my receiver. Where would I even start to look to find someone capable of doing this?

The modification itself is fairly straightforward but it does require one to have some experience in reading datasheets and performing SMD work. Here is the full guide.

You may be able to take your AVR to a local phone repair shop and provide instructions as to what you would like them to do.

 

[harlizzle]

Lmao, soldering and tiny connections might as well be wizardry for me. I watched your video several times and I know it’s beyond my abilities. I’ve been reaching out to stereo repair shops to see if they can do this mod and they all said no. I haven’t seen a phone repair shop where I live in like 20 years


If anyone knows of a person that can do this mod in Los Angeles, I am all ears!


Edit: when you say phone repair you mean cell phone? For some reason I thought of the old rotary phones lmao

 

[sarumbear]

Greetings!

I thought it might be fun to share details of a current project, which involves modifying AVRs with post-DSP SPDIF outputs. This effectively turns any AVR into a fully digital audio processor with room correction, subwoofer crossover/time alignment and EQ functionality.

The potential applications are numerous and I am in the process of producing a rather elaborate video that should enable anybody with moderate DIY electronics experience to perform this modification.

View attachment 106784

The modification itself is fairly straightforward and entails hijacking the front channel I2S output which runs between the unit's DSP and DAC. A readily available WM8804 board can then be used to obtain a stereo coaxial SPDIF output for those channels.

View attachment 106785

I expect to complete production of the video guide within a few weeks. These photos were taken during a quick test, to ensure that my script did not omit any relevant detail. The procedure is applicable to almost any AVR, with pin locations and channel pairings being the only significant variables.

View attachment 106786

This is a cheap, used Denon AVR-2807. It was manufactured in 2006 and was one of the first Denon units to include Audyssey MultiEQ.

The thought had also occurred to me that the AD IC would be fairly easy to control via I2C for arbitrary DSP. Perhaps I'll look into that soon!

Well done!

 

[Weeb Labs]

Lmao, soldering and tiny connections might as well be wizardry for me. I watched your video several times and I know it’s beyond my abilities. I’ve been reaching out to stereo repair shops to see if they can do this mod and they all said no. I haven’t seen a phone repair shop where I live in like 20 years


If anyone knows of a person that can do this mod in Los Angeles, I am all ears!


Edit: when you say phone repair you mean cell phone? For some reason I thought of the old rotary phones lmao

Yes, I do mean smartphone repair.

 

[krabapple]

If it's S/PDIF out that limits the content to either 2-channel, or lossy compressed multichannel (Dolby/DTS) bitstreams.

But I'm guessing you know that already.

I mention it because I don't know how many 'stereo' listeners (those with just two speakers) actually use DSP, e.g. Audyssey, at all.

 

[sarumbear]

If it's S/PDIF out that limits the content to either 2-channel, or lossy compressed multichannel (Dolby/DTS) bitstreams.

But I'm guessing you know that already.

I mention it because I don't know how many 'stereo' listeners (those with just two speakers) actually use DSP, e.g. Audyssey, at all.

What about miniDSP users?

 

[jamescarter1982]

for prototyping a speaker I'm guessing lossy over optical would be fine what is the best all round software for making crossovers etc atm . I could just send straight to my av amp then prototype the crossover in 4th order then order some xkitz modules when I'd selected the correct crossover points

 

[voodooless]

You guys don’t get it. The modification taps the i2s signal from one of the DAC’s and makes SPDIF out of it. This is always stereo at whatever sample rate the AVR DSP runs at for whatever channel pair you choose to expose. If you want more channels, you’ll have to add more SPDIF converters.

 

[krabapple]

What about miniDSP users?

Never owned one, so please excuse my naive questions ...the idea here seems to be , apply some DSP in the AVR, then make the resulting (two-channel) output available digitally,. A miniDSP on top of , say, Audyssey, would be for...applying further DSP? Fine tuning? For 2.x , something subwoofer related ?

 

[sarumbear]

Never owned one, so please excuse my naive questions ...the idea here seems to be , apply some DSP in the AVR, then make the resulting (two-channel) output available digitally,. A miniDSP on top of , say, Audyssey, would be for...applying further DSP? Fine tuning? For 2.x , something subwoofer related ?

You are conflating your question. You asked if people who listen use DSP and I said how about the large number of miniDSP users, which are stereo devices. I was trying to show you that yes, stereo music listeners do use DSP, if not for applying EQ.

 

[Zooqu1ko]

You are conflating your question. You asked if people who listen use DSP and I said how about the large number of miniDSP users, which are stereo devices. I was trying to show you that yes, stereo music listeners do use DSP, if not for applying EQ.

"They" are not all stereo devices, the DDRC-88D here on my desk certainly isn't.

 

[sarumbear]

"They" are not all stereo devices, the DDRC-88D here on my desk certainly isn't.

I stand corrected. I was though thinking of domestic products.

 

[krabapple]

*Anyway* --- the pertinent (if read in context, rather than isolation) question was, what is the expected use case here? DSP applied in AVR, then (stereo) digital signal passed to DSP device 2? In order to....?

What sorts of DSP are envisioned being applied in the AVR?

 

[Zooqu1ko]

*Anyway* --- the pertinent (if read in context, rather than isolation) question was, what is the expected use case here? DSP applied in AVR, then (stereo) digital signal passed to DSP device 2? In order to....?

What sorts of DSP are envisioned being applied in the AVR?

Possibly none. You could just use it as a decoder for Atmos or DTS-X, ignore Audyssey, YPAO or whatever, run all your S/PDIF outs into a DDRC-88D and then into a DAC that's got a top rating right here on ASR. Or enable/use the room compensation and just replace the mediocre DAC in a low end AVR. Digital multichannel outputs aren't available on AVPs that retail for less than 7000$, so adding them to a 500$ AVR may be a really attractive option.

 

[krabapple]

I had to chuckle at 'all your S/PDIF outs' , and the persistent assumption here that are audibly 'mediocre' abound in 'low end AVRs'.

Anyway, carry on.