6-channel analog audio to HDMI audio box?

[Leo Enticknap]

I've just replaced a deceased motherboard CP750 with a CP950 in one screen of an 11-plex, which is the only screen in which the film projector and platter weren't taken out when the place originally converted to digital. There is also a CP500 in the rack, and in the old installation, the master analog output of that went into the multi-channel input of the 750. As has been extensively discussed here earlier, the 950 does not have a multi-channel analog input.

The 35mm system has not been used since the digital conversion, and the owner is not too anxious about it, but if there is a hack that would enable us to get the audio working again, we'd be interested in exploring it. The HDMI input on the 950 is unused. Question: does anyone know of a box that will take 6 channels of line level analog in (ideally balanced, but I'd settle for unbalanced), and spit them out as LPCM audio through HDMI? From looking around online, I can find numerous boxes that will do this in the other direction, and some that will convert analog to HDMI, but two channels only.

[Carsten Kurz]

The only solutions I found in recent years are quite expensive. While you can find a lot of cheap multichannel A/Ds, most of them lack separate AES/EBU outputs. Most have multichannel ADAT or DANTE connectivity, because that has become more common in audio production. You may be able to use 3 stereo A/Ds, each with an individual AES/EBU output, but they need an external sync option. I don't think the CP950 will cope with three unsynced AES/EBU inputs.

[Steve Guttag]

There was one company that had such a thing and it was very pricey. I forget their name as I would never be able to sell it. I also looked into 2-stepping it. Converting the analog to SDI and the SDI to HDMI converter...that "Could" work. There may be some latency to contend with and it just seems hokey. The lack of multichannel analog in is one of the chief reasons that we just don't use the CP850 or CP950. Now, if Dolby were to provide for an AES67 input on their AES67 port, then more opportunities open up with Dante devices too (many Dante devices can also work with straight-up AES67).

My solution has been QSYS...it is always as big as one needs it to be. And, with the new CORE Nano and Flex-8, one can get them as small and as cost effective as need be.

[Carsten Kurz]

That was the ARVUS converter. Yes, very pricey.

You can buy an 8ch AD-DA from Behringer for as little as 160US$ - but it spots 8ch ADAT, not AES/EBU interfaces. Then you would need an ADAT->AES splitter. Available, but, at around 600US$.

There are 4ch analog->AES converters from AJA, but, you would need two for a 6ch solution (2*399US$).

The RME ADI 8 DS does it, but lists at around 1500US$.

If times wouldn't be what they are now, Odyssey could have built something in the low-to-mid hundred US$ probably, but, as it stands now...

[Leo Enticknap]

Thanks folks. I think something in the low to mid three figures would have been viable for this project, but not heading into four figure territory. If ever a more reasonably priced analog to HDMI audio device does become available, that would potentially be a useful hack for enabling film sound through an 850 or 950.

[Carsten Kurz]

There are cheap stereo A/Ds with 2*RCA in and S/P-DIF outputs. One would have to check wether the specific S/P-DIF dialect works with the CP950 AES/EBU inputs, but, it wouldn't be too complicated to use these converters. They are usually clocked from an external crystal clock IC, and it wouldn't be too complicated to pair and sync three of them that way and put them into a small enclosure.

This one seems to use 48KHz:

https://www.ebay.com/itm/A-D-Analog-...EAAOSwA29Y4~5W

[Sean McKinnon]

I have used these Here or similar in the past. You can feed the outputs of the 500 and 950 into it and output two the amplifiers the downside is two separate EQ's the up side is you have two separate signal paths so if the 950 fails you can always throw a used DMA 8+ on the 500 to keep the screen going....

[Leo Enticknap]

So near but yet so far!

The stage speakers are tri-amped. When upgrading the 750 to the 950, I took an existing USL CM series monitor/crossover out of use, and replaced it with the internal crossover in the 950. So I'd need a version of this with at least 14 pairs of channels, and I can't see one on Whirlwind's website. I suppose it would be possible to take two of these units, send the output of the 500 through the USL, and then downstream from that, the two Whirlwind boxes: but that would be around $1,200 in hardware, plus a significant expense in hours for rewiring. By the time that's all done, you're not far shy of the cost of one of those Arvus things.

I suppose another possibility would be to reinstate the USL crossover, and send the output from the Whirlwind box into it. But the USL box is almost a decade old, and therefore a reliability issue.

Many thanks for the suggestion.

[Stefan Scholz]

Carsten,

I assume he's looking for an AES 3 to HDMI multichannel embedder. Not Multichannel analog to linked AES in. The CP 950 does not have any "spare" multichannel AES 3 inputs. They are all used in projector connection.
Analog multichannel to HDMI embedders are expensive. Forbiddingly expensive for a "we may use the analog system in 10 years once" solution.

The CP 950 is a great product, if your system is not going to be too complex, and just simple straight forward movie presentation is the goal.
But QSys is the way to aim, for everything else. When I did our system 15+ years back, we were using Yamaha DME based networked solutions. That is a similar approach, just QSys is more modern.

For a reasonable solution a Yamaha DME 24 comes in mind. This offers 8 analog in, 8 analog out and with the expansion slot 8 ports of AES 3 in and 8 ports AES 3 out. Just create 2 scenes, acting as a switch box, either link CH 1 to 8 from the projector to the AES 3 out, or use the 6/8 channels from the analog PB and feed this thru the internal A/D. It can handle 96 kHz as well.
Still, even though these are commonly available in good used condition around 300 bucks (eg from church groups), this is a little overblown for the purpose intended.

[Carsten Kurz]

The CP950 has 2*8ch digital inputs on two separate RJ45, so, with the proper routing, there should be three physical AES3 inputs possible. One could even use a simple AES3 / RJ45 switcher or patch panel. Multichannel analog to HDMI-LPCM, although technically simple, will certainly remain a very rare species indeed. I've been looking up all sorts of 'Miniconverters' by BMD, AJA, and the like for years, but nothing comes close solving the task. At least not at a reasonable price.

- Carsten

[Leo Enticknap]

I assume he's looking for an AES 3 to HDMI multichannel embedder.

No, analog (not AES) to HDMI.

Splitting the AES into two groups of 8, one for the IMB and the other for an analog to AES device, would be viable, but for the fact that I need 10 channels of digital AES: 7.1 audio, plus HI and VI.

It looks like there is no reasonably priced way of doing this, sadly.

[Carsten Kurz]

There are 3*2 input channels left then. Not that HDMI would be such a bad choice in general, but, analog multichannel to HDMI LPCM - I just don't see that being built. There is no audio only over HDMI, it always needs to travel with some video - even if black. But, what could be the typical purpose of such a converter?
3*2 analog audio to 3*AES 3 is so much easier to build.

[Ethan OToole]

What about using a free PC with 6+ channels audio input? Older laptop with HDMI and multiport sound card or small desktop. On Linux Alsamixer and JACK (kind of a pain to setup) can route this stuff all around. There has to be a way to do it in Windows as well.

[Leo Enticknap]

Nice idea. I can definitely see that working. As you say, all you'd need is a graphics card (either discrete or built into the motherboard) that embeds audio into the HDMI output, plus an audio card that has six channels of analog input, and you're done. I'll definitely check that one out - many thanks.

[Steve Guttag]

You know, if Dolby ever decides that they can do AES67 properly, then there would be a means of getting audio into the CP950 et al. That is, if they could treat AES67 as an input as well as an output. There are numerous means of getting from HDMI to analog, including low-cost (low-longevity, space hogging) consumer AVRs. From there, there are means to go from analog to AES67.