Sound Devices Mixpre-D AES digital output

Throwback

Throwback

Well-known member
Having seen many threads on this and other forums touching briefly on the digital outputs of the Mixpre-D, I am struck by how little clarity there is, after several years of this popular mixer/preamp being available, on a) the quality difference between using the AES digital out and line out and b) the practical use of such, especially with more modest recorders. On the one hand, some suggest that connection to a cheaper recorder such as the Tascam DR 100mkii is straightforward and that the gains are huge: e.g. in the current discussion of budget shotgun mics on this forum John Willett suggests that using the digital out of the Mixpre-D into the Tascam DR100 mkii gives 'vastly better quality than the analogue [i.e. line level] inputs of the Tascam' (http://www.dvxuser.com/V6/showthread.php?314078-Sennheiser-Mke-600-vs-AT-835r) whereas, for example, Matt Mayer of Sound Devices on their forum suggests 'the improvement in sound by using a digital connection vs a line level signal would be incremental at best' and this is in relation to the same recorder (http://forum.sounddevices.com/showthread.php?3456-Sound-Devices-MixPre-D/page2). My personal use is with a Mixpre-D going out by line level to a recorder, based on the facts that I don't have a recorder with digital input (!), and that the background noise of non-studio location recording and the self-noise of microphones used would render too subtle any improvement. But perhaps I am missing a trick and should get a true bit-bucket recorder? More to the point, what would be useful to many with, or considering buying, the Mixpre-D and a recorder would be actual experience (ideally, comparative tests) of the digital out vs line level, and actual experience of the practical problems (and solutions) in connecting the Mixpre-D AES outputs to handheld recorders such as the DR100 Mkii or Marantz PMD661. Cheers, Roland
 
In theory a digital output will be better quality but in practical use an analogue output may be better.

Digital is a high quality interface but has limitations regarding its frequency range and more importantly if you lose a digital interface or it becomes faulty you get nothing on both channels or even worse splats or digital noises.

If you interface via analogue the frequency range is not limited according to the sample rate and if you lose a left or right channel you may still be able to use the remaining one.

Digital interfaces have their uses but for location work where equipment may be moved around a great deal just sticking to analogue may be perfectly acceptable for most uses.

What I would personally do is dual up and feed a camera with an analogue signal but then record locally from the mixer to a recorder via digital as it gives you the best of both worlds.
 
Hi Gary, Some useful general points, though, of course, you could run a dual system with analogue connections (as many do), so this still begs the question as to how much better - from practical experience/testing - is the Mixpre-D audio using the digital connection and what are the practical issues and solutions (including experience of faults during location use, along the lines you describe) in connecting its AES output to those modest handheld recorders with a (S/PDIF) digital input. Cheers, Roland
 
Funny how some of you audio people have names like "Roland" and "Mike".:-Laugh(DBG): Check this YouTube out, which happens to be on topic...

 
Hi EDV, A nice video from my near namesake (which I've seen before), but not really on topic, I'm afraid, as this thread is very specifically about the AES digital output of the Mixpre-D and its use with modest handheld recorders capable of taking a digital signal! Cheers, Roland
 
My take on all this, is that the MixPre-D would have good mic. pre-amps and, I assumed, of the same quality that they put in the 700 series recorders.

A small hand-portable recorder would have analogue circuits built down to a price and some of them have the reputation of being noisy.

Therefore by going through a good ADC in the MixPre-D and by-passing all the analogue circuits of the small recorder will give high quality professional results.

So, going digital in to a Tascam DR100-II or a Marantz PMD 661-2 would be by far the better option than going in via analogue.

There is no frequency range limitation, as someone said, doing it this way as the recording is digital and not analogue - I would far prefer to use the high quality ADC in the SD than the low cost one in the recorder.
 
Hi John, Thanks, but - not least given Sound Devices own reference to the improvement of digital over line-level connection to a Dr100mkii being 'incremental at best' (what's in for them to underplay the advantage of the Mixpre-D AES output?!) - it would be great to hear about the practical experiences of a Mixpred-D and, say, a DR100mkii or PMD 661, not least given the connection difficulties that scattered forum evidence shows others have had. Cheers, Roland
 
Throwback said:
Hi Gary, Some useful general points, though, of course, you could run a dual system with analogue connections (as many do), so this still begs the question as to how much better - from practical experience/testing - is the Mixpre-D audio using the digital connection and what are the practical issues and solutions (including experience of faults during location use, along the lines you describe) in connecting its AES output to those modest handheld recorders with a (S/PDIF) digital input. Cheers, Roland
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Well for a start AES is balanced 5volt signal and spdif is unbalanced .5 volt so you may have problems interfacing, personally I would stick to analogue as the difference will be minimal but you may also need to adapt balanced pro level out to unbalanced prosumer depending on the device you are connecting to.

As said before digital faults can result in no signal at all or splats or pops on the audio but analogue can have its own problems such as hum or intermittent signal but it is far easier to hear and correct as is overload distortion.

There are frequency limitations on all digital transmission systems and 48k has a frequency response up to around 24khz and 44.1 to around 22khz. Way beyond human hearing so in practical use not hugely relevant for prosumer kit but as third and fourth harmonics can be truncated it is why 96k digital recording was brought in for critical applications.

Indeed some old Neve analogue mixing desks can pass audio signals up to 100khz but for most location recording the difference between analogue and digital in practical terms in minimal and you would only notice by comparing two signals recorded at the same time. I would go for safety first and stick to analogue but as John has said it may be that taking the tascam pre amps out of the equation may sound better but for most video related uses I think you are getting into train spotter territory and if you end up with having to get an AES to Spdif converter it is just something else to go wrong in the recording chain!
 
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I'm sure you are right, Gary, and, as I said, analogue line level output is what I currently use for location recording and, given its robustness and background and mic self-noise, is what I imagine continuing to do. I have, however, been running a few tests tonight comparing the digital connection (in the absence of an aes or spdif recorder, I have used the usb output) to line level solution - for example using a Sony m10 - and with a quiet mic (5dba) can hear the difference. This appears significant enough for effects recording, so will have a play with this (using an admittedly less than robust mixpre-d to android tablet set up, but which is at least silent - compared to a laptop - and sufficiently mobile for testing purposes, to see whether or not even this use would merit a more robust digital solution). Cheers, Roland
 
Throwback said:
Hi John, Thanks, but - not least given Sound Devices own reference to the improvement of digital over line-level connection to a Dr100mkii being 'incremental at best' (what's in for them to underplay the advantage of the Mixpre-D AES output?!) - it would be great to hear about the practical experiences of a Mixpred-D and, say, a DR100mkii or PMD 661, not least given the connection difficulties that scattered forum evidence shows others have had. Cheers, Roland
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If Sound Devices said that, I would like to know the context of the original question.

I find it strange that, in effect, Sound Devices are saying that their pre-amp quality and ADC are about the same quality as a portable recorder. In which case - why buy a Sound Devices?

If the person who said that was asked a specific question and said that, under those specific conditions, that the questioner was unlikely to notice much difference, I could understand it. But I do suspect the quote has been taken out of context.
 
GaryNattrass said:
There are frequency limitations on all digital transmission systems and 48k has a frequency response up to around 24khz and 44.1 to around 22khz. Way beyond human hearing so in practical use not hugely relevant for prosumer kit but as third and fourth harmonics can be truncated it is why 96k digital recording was brought in for critical applications.
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Yes, what you say is true - but it is totally irrelevant, as the recording is ending up on a digital recorder. So what you say here can be ignored as all you are doing is moving the ADC later in the chain and adding more analogue noise as the signal stays analogue for longer.

And, remember that modern prosumer kit has far better resolution than top end pro kit of a few years ago.
 
I think we can agree that the quality of recording kit has never been better and a lot of the time it can be more important to actually get on with the job of creating something interesting rather than getting too bogged down in the technical aspects.

20 years ago all we had was DAT and a huge PCM machine that linked to a video recorder. Pretty much the only analogue portable mixer was an SQN and they cost huge amounts and I still own one.

Now we have been thru minidisc to full PCM recording on most cameras and domestic recorders but I always get frustrated that people tend to get worried too much about train spotter type relative quality and don't actually get on with the job of creating content that is interesting or valid.

I almost deliberately don't buy high end kit these days as freelance rates are not what they were and besides I can get more tools to use for even less money and the only way you can tell one from the other is if something is drastically wrong or if it is faulty or by doing an A/B comparison.

So listen to any piece of sound recorded these days and tell me if it was done with a £150 mic or a £1,500 mic or if it was an analogue or digital interface.

Listen to every piece of music that was recorded since 1957 till the present and do you care what mic it was recorded with or what format it was recorded on unless it has technical faults I am sure you will find it hard to tell.

I am always amazed when I listen to those old Frank Sinatra recordings from the 50's and when you hear how they used around three mic's and at best three audio tracks is it really relevant what tools were used but more important what the skill of the operators did with them.

Content is king as they say now get out there and get recording but make sure you record it well with the tools you have to hand.
 
John, Not sure that the doubt implied by 'if Sound Devices said that' is merited! As my original post set out, this was a forum comment (no more, no less) from Matt Mayer of SD on SD's own forum, to which I provided a link (OK, you have to register to look, but I can hardly cut and paste the whole SD thread!). It is clear from this that he hadn't used the combination of Mixpre-D and DR 100 mkii and that it was not some carefully considered result of deep technical analysis, but was an example providing an interesting contrast to your own claim for the digital input to the Tascam giving 'vastly better quality' reflecting what many people do, probably for the pragmatic reasons that Gary has touched on in his posts (i.e. use the line level output and not the AES). As for the bit about Mayer's comments implying that the SD preamps are similar to those of portable recorder, this is far from what he implies - his point is that the main benefit of the SD preamps is getting the mic signal up to line level, and that the degradation - compared to the digital route - of passing this line level signal through the analogue circuitry and ADC of the recorder is relatively minor for - and this is important - the purpose of location narrative recording as described by the person asking for his advice. If he was responding to a question about recording of music in a treated room/studio, for example, his advice may have been rather different! And, of course, the point of my request was for some real-world experience (rather than such varied and - one assumes - fairly off the cuff comments) of the Mixpre-D line level vs digital outputs with budget recorders, which might inform those using or buying relatively modest equipment.

Gary, Yes, I agree with you that it is good to get out there and make the best with any equipment (which as you say, is often so much better than what was commonly available before) and not get too obsessed; but equally I hope that you will agree that part of this involves really understanding your existing equipment (which includes wondering 'so just what does this currently unused AES output on my mixpre-d offer in practical terms for me, or someone similar, outputting to a budget recorder?': the essence of the original post!), and also (for those thinking of buying a mixpre-d and/or a handheld recorder) understanding equipment to make informed and appropriate buying choices.

Cheers,

Roland
 
Well to get the best out of an AES output is to interface it to a recorder with an AES input, the same goes for an analogue balanced output so if your recorder uses prosumer interfacing you might end up with more problems than you started with.

I am a great advocate of keeping things as simple as possible especially on location so you need to try and test to make sure that all your kit works to its best functionality. That goes for equipment choices too so expecting a budget piece of kit to perform and interface with high end pro kit is not the best way to go and why I tend to recommend budget mic's and kit for videography work.

Having said all of that it is acceptable to go balanced to unbalanced analogue at line levels and if the cable runs are short so it should be very easy to hook up your mixpre-D to a tascam that way rather than try to go balanced AES to unbalanced consumer Spdif. A great deal of people also go from the tape output of the SD as that is unbalanced and at consumer levels so will match the tascam or a semi pro unbalanced input better. That will also free up your balanced outputs to feed a camera or another source. I personally do this type of thing with my own Twelco mixer as I have 10-pin hirose to feed the camera on balanced XLR's with 3.5mm jack return as well, Stereo and Mono XLR's to feed IFB or other equipment that needs balanced audio and the unbalanced five pin XLR in/out feeds my marantz PMD 670M but it also has a return that I can listen to.

Of course there is the ultimate test where you plug each one up with your mic and see if you can hear any difference, I suspect you will not but it may be that the analogue has a better sound chain than a digital one that may also cause splats or you to end up with nothing.

I personally only go AES on pro kit and if it is available, I have an AES to Spdif optical and phono adaptor but that is for fixed installations and not location as all my ENG mixers are analogue anyway.
 
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Throwback said:
Having seen many threads on this and other forums touching briefly on the digital outputs of the Mixpre-D, I am struck by how little clarity there is, after several years of this popular mixer/preamp being available, on a) the quality difference between using the AES digital out and line out and b) the practical use of such, especially with more modest recorders.
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Yep. I'm with you there.

You might want to read what Dennis Bohn of Rane Corp. wrote about AES3 to S/PDIF conversion.

What's missing from this market is a decent bit-bucket. What we need, is a small recorder that takes AES3 input via XLR. SD should make one. Tascam. Fostex. Somebody. It should be so small that it just plugs into the AES3 connector of the MixPre-D. Sorta like a Sennheiser SKP 100 plug on mic transmitter. Only smaller and lighter.

It just needs to be big enough for SDHC / SDXC memory cards (or whatever media they want to use). The only interface it needs to make is some kind of display that tells me how much "time" is left on the card, an on/off switch, and a start/stop recording switch.

Maybe it's just me, but this seems so obvious. Why hasn't it been done already?
 
Bruce: thanks for the link - and, yes, we can dream!

Gary: thanks for the latest. I'm happy using the Mixpre-D line level output for location work (in preference to the tape out or AES), but - as I mentioned in an earlier post - will play around further with the USB output to a tablet for quiet effects etc. recording and see if this has any real-world advantage before deciding whether or not its worth getting a recorder with digital input (and this need not be - longer term - a SPDIF device but one with AES).

Cheers,

Roland
 
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