Dolby SDU4 Hardware Dolby Stereo/Surround decoding

[deleted user]

What do you mean by it not being high end? It's a device made for studios.

Sounds like what you're planning could work, however I would wonder whether the digital in is capable of recording ac-3. And losslessly so. Either way, does this whole setup idea mean you're giving up on the idea of bit perfect captures?

[spoRv]

With not "high end" I meant that after all, analog input of the SDU4 would not be on par with a digital input, that's all; I'm sure its quality would be great, as much as an analog Dolby Pro-Logic decoder could be - still curious to know if better than the Shure 5300, though!

About bit-perfect capture: it *should* be bit-perfect capture, unless the Presonus for any reason introduce "something" like some other audio cards do. AC-3 and DTS digital tracks could be recorded padded in PCM and the "extracted" - AC-3 could be used "as is" for DVD or BD (48kHz) while DTS should be converted to 48kHz to be DVD and BD compliant. Of course if the capture is bit-perfect. Let's see when I could put it in action!

[pipefan413]

I was looking around trying to decide whether to buy one of these, or maybe something else more standard for consumer purposes (RCA instead of XLR, less flexibility but designed to "just work" out of the box). I dithered for about a week or so then finally made a decision last night.

So um... I may have just bought not one but two Dolby Surround / Pro Logic hardware decoders.

Ahem.

#1: a Yamaha DSR-70PRO Pro Logic decoder intended for use in consumer home video chains (analogue stereo input, analogue L+R+C+S output)

#2: a Dolby SDU4 decoder intended for use in studio applications (the same one that it seems both @TomArrow and @spoRv have)


Problems I'll have to overcome:

1. My Blu-ray player has no analogue output whatsoever, only HDMI and digital coaxial. However, my PC, PS3 and PS4 can output over decent quality RCA cables, so any of those can probably be used as the input device; I dunno if any of them will produce more or less noise than each other, in terms of getting a clean analogue signal. My assumption would be that the PS3 and/or PS4 may have cleaner sounding analogue output than my PC, but that may be completely wrong; I use the analogue stereo output from my PC just about every day and it sounds pretty good to me, but I'd probably need to really analyse some test audio using really good headphones to tell if it's doing anything iffy to the fidelity of the output (I've never recorded the output from that line out, only played it back in real time).

2. I can't simply chain the Yamaha into my main setup because even if I use analogue input, I have no way to output the 4 analogue RCAs into my AVR, which doesn't have any inputs with more than 2 channels (there are analogue inputs for a number of things but they're all L+R only, so I can't input L+R+C+S). To do this, I would presumably need to somehow get the analogue audio *back* to digital again before chucking it to the AVR, which probably isn't straightforward or cheap. So this is probably only useable as a recording solution rather than a real time one, unless I replace my AVR with one that has surround (4+) analogue inputs, which I don't really intend to do any time soon because I only just bought the damn thing a couple of years ago.

3. I already have a serviceable audio interface but it only has 2 inputs rather than the 4 I'd presumably need to simultaneously capture all 4 channels at once, unless it's possible to funnel stereo rather than mono input through a single 1/4" TLS jack (which I assume I can't do on this interface since there's no indication of that). I could presumably still capture, but it'd mean running through every audio track twice and syncing the first 2 with the second 2 channels (I'd do this by adding silence to the start of the raw PCM and inserting a click at a precisely calculated point, e.g. at 48000 samples, then syncing the clicks and cropping the silence back off precisely to restore the original sync). A tad laborious and slow, but I guess it'd work.

4. Being intended for opposite use cases, one of these requires XLR cables (studio use) and the other RCA cables (consumer use). So I'll have to buy two sets of cables to record both. This was a terrible idea for my wallet...

[deleted user]

Can't answer the questions about making it part of a home cinema system, but can give my 2 cents on question 3.

You need to send both 2 source channels into the SDU4 at the same time. Otherwise the decoding won't work. However you don't have to capture all 4 destination channels at once. If you're using something like Cubase, you can just capture 2 channels at a time and then combine them. They will be already in sync since they will be on a fixed position on the timeline relative to the source track. Then you just export the combined channels and voila.

The XLR inputs on the SDU4 are one per channel.

TRS can be stereo, but I doubt that's the case here, it's usually only the case for headphones and consumer soundcards with the little jack.

About the type of cable ... I think the only difference ultimately (that can have any measurable or audible impact) is bad shielding, which also only plays a role if the cable is running past some strong source of electromagnetic radiation (did I say that correctly?) like a switching power supply. I could be wrong though. But I've never seen any conclusive evidence that golden cables and whatever have any appreciable quality impact. Though to be fair, in the long term there might be a difference in that some materials can oxidize and then not conduct well anymore. I guess that's what the goldening is for? Since gold doesn't oxidize? Or does it? What the heck do I know.

[pipefan413]

Can't answer the questions about making it part of a home cinema system, but can give my 2 cents on question 3.

You need to send both 2 source channels into the SDU4 at the same time. Otherwise the decoding won't work. However you don't have to capture all 4 destination channels at once. If you're using something like Cubase, you can just capture 2 channels at a time and then combine them. They will be already in sync since they will be on a fixed position on the timeline relative to the source track. Then you just export the combined channels and voila.

The XLR inputs on the SDU4 are one per channel.

Yeah, to be clear: I would be sending both L+R to the SDU4 / Yamaha, I'm just saying that I can't capture all 4 outputs simultaneously without getting a new interface with 4+ inputs. Mine only has 2, sadly. (I haven't used it for about 10 years.)

I'm not entirely sure what you mean about them already being in sync unless you just mean they'll be in sync apart from their start points (since I'm going to have to hit "record" at some stage and that'll not be precise). I realise that; it's what I meant about inserting a manufactured spike in the waveform: it gives me a sync reference with which to match capture 1 (2 channels) to capture 2 (the other 2 channels) from the decoder's output. Otherwise, capture 1's 2 tracks will sync with each other by default but capture 2's 2 tracks will need to be aligned with those from cap 1 somehow, and eyeballing it seems unwise when it's easy to just do it calculatedly and match the waveforms.

I'll also be interesting to see how accurate the surround channel delay actually is, because I'll be able to see where that click lands on the surround channel relative to the other 3 channels! The Yamaha has an adjustable 20/30 ms surround channel delay but, as you know, the SDU4 is much more flexible than a simple binary toggle switch.

TRS can be stereo, but I doubt that's the case here, it's usually only the case for headphones and consumer soundcards with the little jack.

Exactly. Some interfaces appear to have a mono/stereo toggle, but not this one. It was a budget Mbox model from ages ago.


I might at least test the two decoders on my 2-input interface just to make sure they actually work at all but if I'm going to be doing captures it'd make a huge difference to be able to cap 4 at once rather than just 2 and then rerun it again for the other 2.

[spoRv]

I dunno if any of them will produce more or less noise than each other, in terms of getting a clean analogue signal.

https://audio.rightmark.org/index_new.shtml

Have fun!

[captainsolo]

The trouble is manufactures dropped multi analog ins which is ridiculous as it's an important feature and essential for those who want to use external amplification. I've wanted to get pro matrix decoders for ages but have no way to run them into my Onkyo-had the same problem with my first rf demodulator which only spits out six rca cables.

But to be honest DPL IIx does a wonderful job. I'd love to be 100% accurate but unless you have super pro gear like that it's going to be hard to beat refined ProLogic algorithms or Neo 6.

[pipefan413]

The trouble is manufactures dropped multi analog ins which is ridiculous as it's an important feature and essential for those who want to use external amplification. I've wanted to get pro matrix decoders for ages but have no way to run them into my Onkyo-had the same problem with my first rf demodulator which only spits out six rca cables.

But to be honest DPL IIx does a wonderful job. I'd love to be 100% accurate but unless you have super pro gear like that it's going to be hard to beat refined ProLogic algorithms or Neo 6.

Exactly.

It looks like more expensive models still have analogue multi-in, and indeed a legacy Dolby Pro Logic mode, but mine doesn't: just digital inputs apart from stereo, (2014, Atmos-gen) "Dolby Surround" and the DTS equivalent (which appears to be called DTS Neural:X except when it's applied to DTS-HD MA encoded content).

I have no way to actually use the Yamaha decoder I just bought unless I also buy more cables and/or an AVR with analogue surround inputs. Cables for the SDU4 are en route since I expect it will be more useful for recording than the consumer grade Yamaha.

[PDB]

Agreed, the lack of external analog input on modern receivers is annoying. I understand that there is not the need as much these days but its still frustrating. Especially, since many high end units (that I can't afford) still have it, like from Denon and Marantz.

But I need external ins since I still use a lot of different 80s and 90s sound decoders for LD and PCM 2.0. For that I use Disclord's (RIP) recommendation of the DTS-610:

https://www.amazon.com/Home-Theater-Conn...op?ie=UTF8

Anyway it converts a 5.1 RCA/analog input, original meant for computer sound cards, to full bit-rate DTS 5.1 which you can connect to your receiver via optical or coaxial. I know its not the full range analog but it's a nice compromise. It would be an even more amazing thing if I could finally figure out how to record DTS...



The only problem is the DTS-610 is getting harder to come by these days.

[spoRv]

Found this nearby: https://line6.com/legacy/toneportux8/

at 190€ is quite expensive, but I looked around and it's difficult to find out audio interfaces with 6 or 8 input - I know that 4 would be enough to capture audio from SDU4, still I'm planning to eventually capture other configurations as full Dolby Pro-Logic, DTS Neo, or even Audissey DSX (for what all this worth, though...)

Question: would be that compatible with Windows 10?