Analog discrete TO HDMI?

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SQLGuy

Member
Joined
Mar 22, 2016
Messages
48
Location
Colorado Springs, CO USA
Hi folks,

I have a couple of quad decoders (CD4 and SQ). My preamp is a Marantz AV7005, which has 7.1 analog inputs, but the preamp does no processing for these inputs... net effect is that things like delay, bass management, and level adjustments, are not applied when using these inputs... and these are the inputs I need for quad sources. This is particularly a problem because the front speakers use an outboard digital crossover and EQ that add about 12ms of delay relative to the side and rear speakers.

I'm thinking that the most elegant solution would be if there were a device that takes 7.1 analog inputs and converts them to HDMI, so I could pass that to the preamp. I have not, however, been able to find such a device. Analog Devices makes some chips that would be great for this, but, while they run only about $12 a piece in small quantity, they appear to require a $10K HDMI adopter license to purchase. A less elegant, but more economically viable, option appears to be to use a custom kernel with a Raspberry Pi, and add an 8-channel I2S ADC. The Raspberry Pi has an HDMI out that, theoretically, can pass the 7.1 audio (with the custom kernel).

Anyone know of any boxes that would do the analog 7.1 -> HDMI thing?

Any other ideas of how to solve this? Two other things I was thinking of were either to add a digital delay processor to add a few ms delay to the rear channels between the quad decoder and preamp, or to first convert quad sources to FLAC4, and play those with the preamp. For the first idea, it's extra processing, equipment, and cabling I'd rather not add... and for the second, it's annoying to not be able to play quad sources live, as well as my not being sure whether the AV7005 can actually play FLAC4.

Thanks,
Paul
 
My solution to this was to get a Creative DTS-610 dts encoder. This will take the 4.0 (or 5.1) analog inputs and output a dts 5.1 digital stream that can be sent to the receiver. Then you can get processing and tone controls with the receiver on the dts stream.
Possibly can still find a DTS-610 on ebay.

vinylguy4
 
The dts converters out there are typically 'core dts' only devices with SPDIF (rca jack) or TOSLINK (optical cable) outputs. If I'm wrong, hopefully this will trigger someone to correct me with a link! :)

Such a thing might hit the mark for convenience and the stepping on of the audio might be a moot point.

If top audio quality is the primary concern, getting an audio interface with at least 8 channels of analog input would be the way to go. Once the audio is digitized and in the computer, you connect your receiver with thunderbolt or hdmi like normal (avoiding dts altogether). Shop for the analog stage quality in the interface as warranted. A used MOTU interface for example might be looked down on slightly by someone who owns Apogee or Prism converters but it would wipe the floor with the low grade consumer stuff like that Creative device. More work and thought for this method but a bigger payoff.
 
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Yes, the adopter license is what stifles small businesses from even using HDMI. I understand proprietary software, but for hardware that is universally accepted in consumer gear it seems to break an unwritten rule. Imagine a fee like that for RCA connectors in the 50's. But i digress.

Motu HDX-SDI comes close, but doesn't output channels in a routing format that a receiver would understand (uses stereo pairs), so needs an audio workstation on a computer.

http://forum.cakewalk.com/Review-of...-as-an-audio-interface-in-Sonar-m2935385.aspx See 2nd line of 7th paragraph.
 
You really do need to pay extra attention to HDMI using devices! There is some 'copy protection gone wild' stuff going on. (The "If they can't even play it then they can't copy it!" school of copy protection.) Don't be afraid to return products and demand full refund when you run across something disabled or locked out that wasn't clear in the product description. If everyone did this, the practice would stop pretty quickly!

There are also products on the market to disable the code that disables your receiver hdmi input if you ended up investing in one of these scammy products that does this. Better to avoid the scams up front though.

Hmmm...
A list of receivers with known restricted inputs would sure be a wonderful reference guide for this site! :)
Or maybe someone already started such a thread?
 
A couple of thoughts, first you may want to look for a used Outlaw Audio ICBM. This device takes multichannel analog audio and performs a very flexible and configurable bass management in the analog stage. It typically fetches about $200 in the used market. But this will NOT address your delay needs. This device would go inbetween your analog quad processor and your Marantz pe-amp.

Another thought is to visit your local pro-audio shop (e.g. Guitar Center). There are lots of multi-channel analog to digital converters for musicians. But most of these have a USB interface that connects to a computer. Maybe then you can use your computer's HDMI output to your receiver. I'm not too familiar with Rasberry pi devices, it may be doing the same for a cheaper price. However, the quality of a A/D converter can affect your sound quality, so maybe going with an external unit would yield better results.
 
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The DTS-610 looks interesting, thanks for the pointer on that device.

However, for live playback from multi-channel analog to digital, I think a Raspberry Pi based solution may be worthwhile. I'm probably going to back-burner that though, and instead focus for now on my conversion workflow instead... either to DVD-A or FLAC4. I've got some questions on that that I'm going to put into a separate topic.

Behringer makes a nice unit called the U-Phoria 404, or close to that. It's a 4-channel 24/192 outboard ADC and mic preamp. It's USB 2.0. Too bad there's not a way (that I know of) to just stream that output through to a digital input on the AV7005. I do think this device will be handy for conversion, though.

Thanks,
Paul
 
I used to own the DTS-610 and while it did work, I found the sound quality to be such a downgrade that I quickly stopped using it. The D/A converters in that device and maybe the realtime 44kHz DTS encoder chip just aren't very good. If you can afford it, buy something better. Really.
 
If you can digitize the analog source and get it into the computer you can use a DAW app for speaker management as needed.

So you have FLAC files from digital releases and now some FLAC files you made from your analog sources.
Media player app -> route through DAW app -> output to receiver via HDMI

A DAW app like Reaper will give you the ability to do literally anything required for your system or for the odd flawed release. Everything from picking your own crossover frequency for any bass speaker management needed (or calibrating any odd speaker array) to correcting a polarity reversed channel on a flawed release.

For system management, setup will involve some fiddling around but once you dial it in it's just plug and play.

There is a virtual audio device app called Soundflower for routing audio between different apps on the computer. There are a few others too (Jack is another I've heard of.)
Make an aggregate device of Soundflower virtual device + your connected receiver or other audio interface that you use for output.
Select Soundflower for an output device for the computer system.
Make a DAW session that uses the aggregate device. Pick up the incoming audio from Soundflower. Dial up your routing and whatever speaker management you might need. Send the output directly to the receiver or other audio interface.

Right... so this maybe isn't Saturday morning cartoon easy! But either is pecking at front panel controls on a surround receiver. And if the receiver forces you to compromise...
After you set this up, you just switch your system audio to Soundflower in your audio control panel, launch your DAW session (think of this like a 'plugin' for your media player), launch your favorite media player and just hit play.

This setup obviously isn't going to resonate with everyone but it can be a powerful full featured setup that gives you a way to solve any problem that comes along.
 
If you can get it into a pc, you could use something as cheap as Plogue Bidule software and set up your delays however you need them, I would think.
Well I just looked and Plogue Bidule is considerably more expensive than when I bought it years ago but it's only $95 now, chump change for those of you not living on retirement funds like me. lol.
https://www.plogue.com/store/
 
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