AVR With Best Digital Volume Control For Digital Output Mod

[robinasu]

Hi all, just starting my exploration phase to mod a modern ATMOS AVR/Processor with AES/SPIDF outputs. Last I was poking around years ago the pre/pros all seemed to have an I2C controlled or similar analog volume IC's. My Meridian digital speakers have a volume control, but I want to set and forget their volume control.

Can anyone recommend which AVR/Prepro has the best digital volume control? I want to tap the I2S right at the DAC inputs. The current line of Denons and Yamahas have great digital features.

Thanks for your help!

 

[DMill]

Hi all, just starting my exploration phase to mod a modern ATMOS AVR/Processor with AES/SPIDF outputs. Last I was poking around years ago the pre/pros all seemed to have an I2C controlled or similar analog volume IC's. My Meridian digital speakers have a volume control, but I want to set and forget their volume control.

Can anyone recommend which AVR/Prepro has the best digital volume control? I want to tap the I2S right at the DAC inputs. The current line of Denons and Yamahas have great digital features.

Thanks for your help!

Welcome. I’m also in the market for an AVR. Of what has been reviewed on this site, the current Denons have measured better. Of course not all models for either brand have been tested. The good news it’s pretty easy to audition them. Both brands are pretty common if you live anywhere near a metro area.

 

[sarumbear]

Hi all, just starting my exploration phase to mod a modern ATMOS AVR/Processor with AES/SPIDF outputs. Last I was poking around years ago the pre/pros all seemed to have an I2C controlled or similar analog volume IC's. My Meridian digital speakers have a volume control, but I want to set and forget their volume control.

Can anyone recommend which AVR/Prepro has the best digital volume control? I want to tap the I2S right at the DAC inputs. The current line of Denons and Yamahas have great digital features.

Thanks for your help!

You said you are looking a processor for an Atmos setup. How do you plan to connect 8+ speakers digitally?

 

[FrantzM]

There is someone on ASR, @Weeb Labs . He has a detailed Howto. I am surprised more people have not tried it... Send a Private Message to him, he may help.
This is quite involved and you need to be able to read, interpret a schematic, and wield a soldering iron.. Not for the faint of heart or first-timer but, yeah! it can be done. You pick up the digital signal (not sure if it I2S) before it's converted to analog to be sent to the amplifiers in the AVR and send these m to... wherever.. You would know exactly where if you are thinking about this solution...

Peace

 

[robinasu]

I ran across the Weeb Labs vid last week.

I can read schematics and solder pretty well.

Like Frantz mentioned, you tap a spidif or AES converter into the input of the DACs. Meridian speaker have coax spidif inputs. In the speaker you select L/R, then there is a coax output that sends the other channel to the other speaker. Need to understand the architecture. For example, if I recall, my Integra reconfigures the DAC inputs based on settings to get more dynamic range out of the DACs. So, I'm really looking for a cheap, full featured AVR with good digital volume control that doesn't any fancy DAC reconfiguration based on direct in, number of channels selected, etc. Only need a 7.1, so I might pick up a cheap Denon AVR and operate.

Anybody have a good source for Denon service manuals?

I want a well implemented digital volume control on the candidate AVR so I can use HDMI-CEC easily and set and forget the Meridian volumes.

 

[Doodski]

Anybody have a good source for Denon service manuals?

I google the specific model followed by "Service manual" and I often get results. Sometimes one needs to pay $ for it though but each time they have been quality pdf's.

 

[abdo123]

You might wanna try the AVR before you mod it first for SINAD nervosa.

 

[FrantzM]

Hi

From what I understand the AVR would still control the volume. The digital streams comes to the amplifier via some DACs. These do not control the volume, rather the AVR volume control continues to function, in fact all the processing , including DCR, etc are already performed. You present these signals to a multi channel DACs or a group of DACs, although, individual clocks in the DACs may drift apart if they aren’t slaved to an unique clock. How much drift? I don’t know. Would such drift be audible ? IDK either.

Peace

 

[sarumbear]

I ran across the Weeb Labs vid last week.

I can read schematics and solder pretty well.

Like Frantz mentioned, you tap a spidif or AES converter into the input of the DACs. Meridian speaker have coax spidif inputs. In the speaker you select L/R, then there is a coax output that sends the other channel to the other speaker. Need to understand the architecture. For example, if I recall, my Integra reconfigures the DAC inputs based on settings to get more dynamic range out of the DACs. So, I'm really looking for a cheap, full featured AVR with good digital volume control that doesn't any fancy DAC reconfiguration based on direct in, number of channels selected, etc. Only need a 7.1, so I might pick up a cheap Denon AVR and operate.

Anybody have a good source for Denon service manuals?

I want a well implemented digital volume control on the candidate AVR so I can use HDMI-CEC easily and set and forget the Meridian volumes.

I think SPDIF is limited to compressed 5.1.

Isn’t what feeding the SPDIF feed into directly the Denon AVR achieves what you want to do?

 

[FrantzM]

@sarumbear

@Weeb Labs video is a DIY procedure. Invasive. You have to dig inside the NVR, find the output of the modulator chip which is digital and is composed of all the channels supported by the NVR, properly decoded, managed, corrected, Audyssey-ed or Dirac-ed or whatever-ed... These digital streams in the AVR, are usually presented to DACs in the AVR where they are converted to analog, signals to be fed to the amplifiers built-inside the AVR... So ATMOS, 7, 9 or 11 channels are presented independently to the amplifiers inside the AVR.. The procedure is to intercept these digital streams (which are not necessarily SPDI/F) and present each stream to a DAC, from there to your chosen amps.. You would likely void the manufacturer warranty in doing so ... but hey ... If an adventurous soul dreams of a DIY ersatz Trinnov-Lite ? Why not try with an old AVR and see what gives?

 

[sarumbear]

@sarumbear

@Weeb Labs video is a DIY procedure. Invasive. You have to dig inside the NVR, find the output of the modulator chip which is digital and is composed of all the channels supported by the NVR, properly decoded, managed, corrected, Audyssey-ed or Dirac-ed or whatever-ed... These digital streams in the AVR, are usually presented to DACs in the AVR where they are converted to analog, signals to be fed to the amplifiers built-inside the AVR... So ATMOS, 7, 9 or 11 channels are presented independently to the amplifiers inside the AVR.. The procedure is to intercept these digital streams (which are not necessarily SPDI/F) and present each stream to a DAC, from there to your chosen amps.. You would likely void the manufacturer warranty in doing so ... but hey ... If an adventurous soul dreams of a DIY ersatz Trinnov-Lite ? Why not try with an old AVR and see what gives?

I miss-read your post. I thought you said SPDIF input, hence my post. Sorry.

Trinnov, Lyngdorf, Datasat and Stormaudio all have AES outputs. They are pretty expensive units.

 

[MCH]

I find @Weeb Labs video very cool indeed. I don't have a use or interest for an AVR nor any multichannel stuff but i can imagine someone buying a used cheap broken avr and giving it a second life paired with active speakers with digital inputs.

Just out of curiosity: do avrs always work with a dac chip per each pair of channels? What if they use one dac chip to process several channels? Is it still possible to extract various 2 channel spdif signals from those?

 

[sarumbear]

I find @Weeb Labs video very cool indeed. I don't have a use or interest for an AVR nor any multichannel stuff but i can imagine someone buying a used cheap broken avr and giving it a second life paired with active speakers with digital inputs.

Just out of curiosity: do avrs always work with a dac chip per each pair of channels? What if they use one dac chip to process several channels? Is it still possible to extract various 2 channel spdif signals from those?

SPDIF is a 2-ch signal

 

[abdo123]

I find @Weeb Labs video very cool indeed. I don't have a use or interest for an AVR nor any multichannel stuff but i can imagine someone buying a used cheap broken avr and giving it a second life paired with active speakers with digital inputs.

Just out of curiosity: do avrs always work with a dac chip per each pair of channels? What if they use one dac chip to process several channels? Is it still possible to extract various 2 channel spdif signals from those?

No not at all, they almost always have multi-channel chips. But each input (channel) on the chip is delivered via 1 or more pins.

The Weeb labs video is quite messy (i'm talking about the work involved, not the skills nor the result) because of it.

 

[robinasu]

SPIDIF can transmit 2 channel PCM and 5.1 compressed surround (DD, DTS).

In circuit boards other protocols are used, mainly I2S. SPIDIF/AES was made for cables, but for different markets.. SPIDIF for consumer and AES for pro audio (recording industry and concerts market).

Virtually all the DACs out can accept I2S from the DSP section upstream. The DSP section does the surround processing, etc. The fancy AVR/pre-pros do "fancy" analog stuff after the DAC's, like analog volume control and ganging DACs together. I don't want any of that for this project- just a cheap digital signal chain with a good/great digital volume control in the DSP section. I'll have to look for service manuals for the latest Denon AVRs.

 

[Weeb Labs]

I would like to point out that while a schematic is always very helkpful, it is by no means a requirement if you are familiar with various DAC part numbers or are willing to spend some time with Google in order to identify the DAC on your AVR's DSP board. Datasheets are readily available for almost all DACs.

 

[voodooless]

I would like to point out that while a schematic is always very helkpful, it is by no means a requirement if you are familiar with various DAC part numbers or are willing to spend some time with Google in order to identify the DAC on your AVR's DSP board. Datasheets are readily available for almost all DACs.

Well, if you want to know up-front what chips are used and especially what kind of volume control is used, it is definitely recommend. DAC chips used is often easy to find, volume control not so much. Otherwise we would have had an answer to the original question by now.

 

[Weeb Labs]

Well, if you want to know up-front what chips are used and especially what kind of volume control is used, it is definitely recommend. DAC chips used is often easy to find, volume control not so much. Otherwise we would have had an answer to the original question by now.

To my knowledge, all consumer AVRs make use of digital analog volume control and this has been the case for more than 20 years.

There are several fairly straightforward solutions that OP may wish to consider regarding external volume control. One of them is to loop a microcontroller's ADC through one of the NJU's (most common control IC series) channels, read the value and use that to drive an external PGA4311U-based volume control board such as the qualVol. This would keep the AVR's volume knob functional.

Another option is simply to ignore the AVR's onboard volume control and make use of an external potentiometer or encoder to drive a pair of quadVol boards.

There also exists the possibility of sniffing the NJU's I2C bus but that would be somewhat more complicated.

 

[voodooless]

To my knowledge, all consumer AVRs make use of digital analog volume control and this has been the case for more than 20 years.

Probably… one wonders why? DAC SNR is good enough to keep it in the digital domain, and it’s way cheaper…

There are several fairly straightforward solutions that OP may wish to consider regarding external volume control. One of them is to loop a microcontroller's ADC through one of the NJU's (most common control IC series) channels, read the value and use that to drive an external PGA4311U-based volume control board such as the qualVol. This would keep the AVR's volume knob functional.

Another option is simply to ignore the AVR's onboard volume control and make use of an external potentiometer or encoder to drive a pair of quadVol boards.

Well, the OP’s issue is that he’ll be feeding his speakers directly with the digital signal, so he needs to have the volume control in the digital domain.

 

[Weeb Labs]

Well, the OP’s issue is that he’ll be feeding his speakers directly with the digital signal, so he needs to have the volume control in the digital domain.

The simplest approach in that case would be to make use of a cheap ADAU1701 board such as the APM2 in slave mode. He could feed the I2S clocks and all four data lines directly to it and then out to a few SPDIF encoders. The 1701 would handle digital volume control and has GPIO to spare. At 48KHz, this would introduce only one millisecond of additional latency.