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SPL MixDream analog DAW summing

Okay, I'm taking the high road. After so much reading this past year on analog summing amps, then finally listening to some samples, its definitely what I need. This unit takes that ITB closet sound (I've been going nuts trying to overcome) and opens your mix up into a warm fat sound. No wonder they call it MixDream.
Reading this shootout ( [="http://www.studioreviews.com/summing-box-shootout.htm"]Summing Box Shootout[/]="http://www.studioreviews.com/summing-box-shootout.htm"]Summing Box Shootout[/] ) it logically makes the biggest improvement when starting any project from scratch. This could be why some don't see the value.
Plug a stereo comp into it and you have a nice package.
I'm getting the MixDream this month and will be dreaming about it until it arrives. I'll keep you posted.

I found these clips over on PSW forum.

check them out.

[[url=http://="http://www.ma-mfg.com/adam/OTB%20Sumthang.wav"]http://www.ma-mfg.com/adam/OTB%20Sumthang.wav[/]="http://www.ma-mfg.com/adam/OTB%20Sumthang.wav"]http://www.ma-mfg.com/adam/OTB%20Sumthang.wav[/]
[[url=http://[/URL]="http://www.ma-mfg.com/adam/ITB.wav"]http://www.ma-mfg.com/adam/ITB.wav[/]="http://www.ma-mfg.com/adam/ITB.wav"]http://www.ma-mfg.com/adam/ITB.wav[/]

Anyone else have one? I'd love to hear what you are doing with it or how you've set it al up?

Comments

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17 years 8 months

Jeemy Thu, 02/25/2010 - 07:24

Ah yes I missed that follow-up point, and while I think its a pertinent question, I'm not qualified to say either in mathematical terms or practical. However although I may be wrong, I'd put forward that your equation needfully oversimplifies and although its true, the summing of x waveforms amounts to more than a simple a + b sum.

I also don't see why one would preclude the other; why you wouldn't still be using your colourful 2-channel unit to process the resultant 2-bus stereo mix; this would be a good idea, if appropriate, regardless of which type of summing. So I don't think anybody is saying that analog summing is preferable or an alternative to a colourful preamp; just that it is a valid alternative to digital summing with possible benefits.

But I guess, and again I may be wrong, that what we are actually talking about is not just analog summing, but converting 16 channels of digital audio to analog rather than 2 converters handling the entire conversion process. This may well mean (a total guess on my part) that part of the improvement is imparted by an imperfect converter converting a simpler wave (16 times) rather than 2 imperfect converters working on much more complex waves?

How large these benefits are is what your test would prove and it may be something one of the proponents using the Mixdream or similar can produce, although I understand subjective volume levels would be a factor to watch out for. I'll probably step out from the conversation now, I'm very interested in it all but not experienced enough to do more than try and clarify things for myself and watch from the sidelines.

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IIRs Mon, 02/22/2010 - 02:03

Boswell, post: 300230 wrote: One of the major requirements for an external summing unit is large headroom

You mean something like 32/64 bit floating point?

RemyRAD, post: 300246 wrote: You just can't have all the numbers line up perfectly in digital summing.

If the numbers don't "line up perfectly" its a software bug. Try summing the same set of stems in a bunch of different DAWs: I'm prepared to bet that they all null perfectly, ie: every DAW will produce the same identical and perfect results.

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Boswell Mon, 02/22/2010 - 02:30

We've got two different arguments going on here. The original one (paraphrased) was: what sort of conditions would make it worthwhile to take multiple tracks (or stems) out of the box, convert them to analog, perform analog summing and reconvert to digital? The second argument that got conflated with the first was whether different all-digital summations, done ITB or OTB, are audibly different.

So IIRs' comment about floating-point in response to my post about needing good headroom in an analog summing unit is addressing the second argument in a reply to the first.

In terms of digital summation, there are two other points that cause confusion. The first is that it is not expected that all digital summations will arrive at exactly the same numbers, as the rounding algorithms could well be intentionally different between implementations. What matters is how the result sounds, and it is quite likely that some implementations sound better than others. The second point is that in a properly designed digital system, time delays in the sequential addition arithmetic play no part, as all the additions required for the next sample are performed within one sample time. I am referring here to PCM digital systems; things get more complicated in DSD processing.

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IIRs Mon, 02/22/2010 - 02:39

Boswell, post: 300416 wrote:
it is not expected that all digital summations will arrive at exactly the same numbers, as the rounding algorithms could well be intentionally different between implementations.

There may be differences between ITB summing using floating point maths and digital summing in a digital mixer or PT HD hardware using integer maths, but these differences are down at about -140dBFS and I simply don't believe they are significant. Especially if (like Remy) you turn up your nose at 24 bit audio and still use just 16 bits...

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Boswell Thu, 02/25/2010 - 08:31

This is an interesting discussion, and to add more ingredients to the pot, I'll throw in the following:

(a) In an analog summing setup, if the D-A, A-D conversion and the summing processes were perfect and the channel gains all perfectly matched, the result would sound identical to a correctly-computed digital summation. But nothing is perfect, and in fact, we tend to like imperfections of the right sort, for example, low-level second-harmonic distortion increasing with signal amplitude. These imperfections are often called "flavour" or "colour". The trick is how to manage the acceptable or even wanted imperfections while not introducing unwanted ones.

Furthermore, in a typical pop/rock/folk music mix, we often like the different sound sources in the recording to have their own separate colours. This is mostly achieved by suitable choice of microphone and pre-amp for the various instruments and vocals, but more can be applied at the mixing stage on a track-by track basis. Once the tracks are balanced (for level) and summed, for the mix/summing engineer simply to slap a dynamics/EQ/effects unit on the stereo bus does not give us the same feel to the resulting mix. Instead, it is down to the art of the mastering engineer to apply subtle sculpting to the final mix to bring the recording up to release standard.

Out of interest, a parallel thread to this one discusses the use of M-S techniques at the final mix and mastering stages to give an added dimension for imparting effects, EQ and colour that would be either very difficult or impossible to achieve by processing solely on the L-R stereo bus information.

(b) The process of external analog summation is more than simple addition of signals. For example, the panning of tracks to their intended place in the stereo field is in itself not as simple a process as first appears. Most analog mixers and summation units implement one or more “panning laws” that govern the amplitude modulation that is applied to the L and R mix contributions as a track is panned. A general consensus might be that a track panned centrally should have a 4.5dB gain reduction applied to both the L and R components referenced to 0dB and infinity when panned hard to L or R.

Hence it is necessary to specify what functions exactly the external summing device implements. If all the level balancing and panning is performed in the DAW, with each DAW track being output in stereo so its place in the stereo field is determined, the summing unit can work at the same fixed gain for each input and use independent summing of L and R outputs. Note that in this case, the D-A converters may be operating a long way below their maximum outputs, but their noise floors all add the same amount. By contrast, many types of external summing unit also perform balancing (i.e. have faders or rotary amplitude controls for each input channel) and also panning. In this way, each mono DAW track needs only a single D-A converter, which can be operated close to normalised, resulting in a lower noise floor in the final mix. This technique does mean that the mixing and panning are neither stored in nor are under control of the DAW. These two cases are the extremes, and schemes that fall between the two are often used.

(c) I'm certain I could pick out a mix done by hand-crafted analog summation on top-drawer equipment from a straight ITB digital summation, but probably because they would not be the same mix. With reference to (b) above, I don't think it's likely that they ever would be the same mix. Maybe we should put more effort into options for digital summing, and not simply say that the machine always adds up correctly.

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IIRs Thu, 02/25/2010 - 08:37

Jeemy, post: 300718 wrote: , the summing of x waveforms amounts to more than a simple a + b sum.

Summing is summing. It really is just adding up a string of numbers, and is by FAR the simplest calculation your DAW has to handle during mixdown.

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IIRs Thu, 02/25/2010 - 08:45

Jeemy, post: 300718 wrote:
But I guess, and again I may be wrong, that what we are actually talking about is not just analog summing, but converting 16 channels of digital audio to analog rather than 2 converters handling the entire conversion process. This may well mean (a total guess on my part) that part of the improvement is imparted by an imperfect converter converting a simpler wave (16 times) rather than 2 imperfect converters working on much more complex waves?

You can test that theory using the same method Ethan Winer used in his audio myths workshop: play a full mix out of your DACs, and record it back via your ADCs. If your theory that the converters cannot handle a complex signal is correct you will be able to hear that degradation in the re-recorded result. If you can't hear a difference, do the same thing again, and again, and see how many generations you need to go down before you start to hear a difference.

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Jeemy Thu, 02/25/2010 - 11:44

Well just leave that theory, its not mine, somebody else can look after it. All the test would prove is same-in, same-out, not whether 16 direct D/A outs are better overall than 2 digitally summed.

But with regard to this equation: (a*x)+(b*x)+(c*x)=(a+b+c)*x

When you mentioned it, you weren't talking about DAW summing, or have I misunderstood? You were talking about analog summing and saying it should be no different if the summing box sums 2 channels from summed DAW 16-channel audio, than if the summing box sums 16 seperate stems. If analog is imperfect and this is a more complex equation then that cannot be true. The equation is mathematically true for digital domain only?

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IIRs Thu, 02/25/2010 - 12:25

Jeemy, post: 300739 wrote:
But with regard to this equation: (a*x)+(b*x)+(c*x)=(a+b+c)*x

... If analog is imperfect and this is a more complex equation then that cannot be true. The equation is mathematically true for digital domain only?

Actually it would depend on the nature of the imperfections. It they were linear (like an EQ) then my statement would be equally true of analog and digital systems. It they were non-linear (like distortion) then it would be equally un-true of analog and digital.

So it comes down to determining the precise nature of those analog imperfections. From the SPL Mixdream specs:

"Freq. Response: ‹1Hz-220kHz (+/- 3dB)".

But that doesn't tell us much about what's going on in the audible range. If there are +/-3dB swings in frequency response within the 20Hz to 20KHz range, that would certainly be audible and would impart a definite colour to mixes. But the colour would be exactly the same if you ran 2 channels, or 8 stems, or 48 individual tracks.

"THD+N Ratio: -104dB
(20Hz-22kHz, Input +10dBu, all channels active)"

That's pretty clean, wouldn't you say? Distortion definitely would be different for a whole mix compared to seperate stems. But distortion at those levels...?

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IIRs Thu, 02/25/2010 - 12:59

I'm not actually sure that we are disagreeing about anything, except perhaps:

Boswell, post: 300725 wrote:
(c) I'm certain I could pick out a mix done by hand-crafted analog summation on top-drawer equipment from a straight ITB digital summation, but probably because they would not be the same mix. With reference to (b) above, I don't think it's likely that they ever would be the same mix.

Logically: how would you know which mix was which? (assuming someone else mixed them of course!) And have you ever tested yourself?

I think it should be possible to do the test properly, if a little laborious: you would need to first create the mix using your summing box gains and pans (so that your mix desicions could be influenced by any analog gain staging non-linearities), then solo each of your stems, bus them internally as well as routing them to the individual outputs, and use meters to match levels and pan positions to the desired level of accuracy. If you have a DAW that lets you type in parameter values directly you should be able to match these to within 0.1dB fairly easily.

Of course, all modulation effects would need to be printed first, so that playback was identical for every pass.

Boswell, post: 300725 wrote: Note that in this case, the D-A converters may be operating a long way below their maximum outputs, but their noise floors all add the same amount.

This got me thinking: if you were running 16 analog outs as 8 stereo stems, that is indeed 8 different noise floor instead of 1. They would all be uncorrelated (I think?) and would therefore each add 3dB to the overall noise floor. So 7*3=21db extra converter noise from this setup. Have I got the maths right...? :confused:

Boswell, post: 300725 wrote: Maybe we should put more effort into options for digital summing, and not simply say that the machine always adds up correctly.

Not quite sure what you mean by that. care to elaborate?

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IIRs Mon, 02/22/2010 - 07:24

Boswell, post: 300416 wrote: We've got two different arguments going on here.

Lets ignore the OTB digital summing for now as its just confusing the issue.

The way I see it there are two different arguments in favour of analog summing:

1. Summing ITB is flawed somehow, and analog summing is more accurate.

2. Analogue summing adds subjectively desirable colour to an otherwise too perfect digital sound.

As far as I am concerned #1 is BS of the first order, and is a myth perpetuated by people with no understanding of digital audio, or (worse) with a vested interest in selling analog summing devices. Summing = adding together a string of numbers, no more, no less. Anyone who claims any different is either selliing snake oil, or has been conned into buying it.

#2 seems more plausable to me. But I still fail to see why analog 'summing' would be any different from summing digitally and then running the stereo mix through a suitably colourful 2-channel unit. Which (for probably the same money as an 8 channel summing box) might actually provide other useful features like compression or EQ. There are genuine mathematical (ie: non-voodoo) reasons why analog compression or EQ might be technically superior to its digital equivalents (read up on aliasing and Nyquist theory).

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Jeemy Thu, 02/25/2010 - 18:20

I'm not very sure how to quote things. I also know I said I would step down from this. However, I'm really enjoying learning from what you are telling me, so if I may ask a few more questions, hopefully its clear which parts I am quoting from:

re: +/- 3dB swings and nature of imperfections: surely a 3dB variance per channel across 16 channels equates to a 3x16dB variance total, or some equivalent, summed, across the mean? so 2 does not necessarily equal 8, 16 or 48 in this example - as if the imperfections were predictable, they would not be variances as quoted but true, and predictable, imperfections.

Please can you clarify exactly what you mean by linear and non-linear imperfections in analog and digital systems, for both myself and others reading this.

When you say:

Actually it would depend on the nature of the imperfections. If they were linear (like an EQ) then my statement would be equally true of analog and digital

How can this be? Why would the imperfections or variances be identical in both systems? Surely what we are discussing in theory is the reasons why the two would differ? I'm curious to know why the situation arises where given 2 very different signal chains, we are contesting that all factors are equal?

Assuming for a second that factors are not all equal, that summing equations produce audible artifacts, disregarding whether analog or digital are better, yes, Boswell, please elaborate - where do the digital options start making themselves known? Do they impart flavour also?

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AudioGaff Thu, 02/25/2010 - 20:13

Good points Jeemy. Saved me from typing many of the same comments.

True, I can't hear digital summing artifacts down in thenoise floor, but I can hear a difference from a mix done in Cubase 5 or Sonar 8.5 using my Tascam DM-4800 as the ITB playback, compared to the same mix summed on my Tascam DM-4800 using the same levels and mix moves. How can that be. They both do "simple math summing"

Mix on a Mackie 8-bus then mix on a SSL, Neve 80 series or API and tell me if it is different? Heck, Mix on SSL and then Mix on API. Still hear a big difference?

Using the ITB argument, then they should be the same. After all, each one can perfectly null, they all are at least 20-20k, all likely within +/- 3dB, good THD specs.

More to the point, perfect nulling means very little in the scheme of things. I am a real electrical and an audio engineer that understands most all things digital audio as well as analog. While I usually like to know, I don't have to know, or care about the the reasons, or the details, or the science or the technology. I hear what I hear, and I like what I like.

I, like many others, feel ITB mixes suffer from something that we perceive as unpleasant or not up to par as we think and feel that they should be. It is something that is consistant from song to song, project to project. If we use diffferent DAW software and/or different converters, it is still there. Interesting enough, it would seem that analog summing through very good connerters offers a third midway kind of result. I have experienced that indeed, sometimes it was an obvious improvement. Sometimes it made no difference, but it never seemed to make things sound worse. With analog summing you also can add the capability to insert other great analog gear while you sum. When you do that, it can easily lean towards being better than just ITB most of the time.

The whole thing could very well be related to your audio background. If you have had a lot of experience with great analog mixing, then you have that as a reference. If you have not had that, then your not even really qualifed to discuss it without at least having shared some kind of frame of reference.

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bigtree Mon, 02/22/2010 - 09:51

Good thread.

I, by no means have the same tech understanding as you guys and most likely never will. I just don't have the space in my head for an equally creative and technical world so I rely on you guys when it comes down to the tech stuff. When in doubt though, I always trust my ears at the end of the day. We all agree its all about our perception and how we arrive there and I think this always takes us to a stalemate.

IIRs, are you "technically" saying, OTB analog summing is all just snake oil, trickery? It sounds like you are suggesting manufacturers and companies selling these products see this as an opportunity to take advantage of the less technical savy recordist that have no clue. Man, I find this hard to believe. But, based on my ears, I've made the commitment and I'm still excited. The older I get, the more I wish I never sold most of my analog gear, especially keyboards. Digital audio is really clean but its missing warmth.

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IIRs Fri, 02/26/2010 - 01:31

Jeemy, post: 300760 wrote:
Please can you clarify exactly what you mean by linear and non-linear imperfections in analog and digital systems, for both myself and others reading this.

Linear means the change is the same regardless of signal level. Non-linear means the change depends in some way upon the signal level.

A good example of linear would be a simple volume change: if you turn down all your faders by 3dB you get exactly the same result as if you turn down the masters by 3dB and (ignoring the slight difference in headroom and noisefloor in the analog version) this holds true for analog and digital mixing. Likewise, an EQ can be thought of as a frequency specific volume control, so if you notch out 3dB at 3KHz on every single channel, you get the same results as if you notched out that frequency on the master instead.

A compressor is linear so long as the ratio is 1:1 (hence the straight diagonal line you see in the transfer graph of some plug-ins) but as soon as you wind the ratio up you introduce a non-linearity, and the results start to depend on the incoming signal level. Inserting a comp on every channel is obviously NOT the same as inserting a comp on the master, even with identical settings. The same applies to distortion; loud signals are affected much more than quiet signals, and because the artifacts are level-dependent we also get inter-modulation effects when distorting the whole mix that would not have been present when distorting individual channels. Again: equally valid for analog and digital systems.

Of course, an analog EQ will have a much smaller linear range than a digital EQ. Part of the craft of analog mixing is to set your gain staging to stay within the linear range of the equipment. Perhaps the artistic side comes in when you begin to deliberately exploit the non-linearities at the extremes; that's not something I can do with gain staging ITB, but I could load a saturation plug instead...

Jeemy, post: 300760 wrote: re: +/- 3dB swings and nature of imperfections: surely a 3dB variance per channel across 16 channels equates to a 3x16dB variance total, or some equivalent, summed, across the mean?

They are all running in parallel, so they won't accumulate as you imply: that would require you to patch the output of each channel into the input of the next so one signal passed through all channels in series. To return to the volume example: if you turn 48 individual channels down by 3dB you get the same result as turning the masters down by 3dB. 48 * 3 dB = way too much!

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IIRs Fri, 02/26/2010 - 02:10

AudioGaff, post: 300770 wrote: ... I can hear a difference from a mix done in Cubase 5 or Sonar 8.5 using my Tascam DM-4800 as the ITB playback, compared to the same mix summed on my Tascam DM-4800 using the same levels and mix moves. ... they should be the same. After all, each one can perfectly null,

Are you saying that your internally summed mixes null perfectly with your externally summed mixes, but you can still hear a difference...?

AudioGaff, post: 300770 wrote: Mix on a Mackie 8-bus then mix on a SSL, Neve 80 series or API and tell me if it is different? Heck, Mix on SSL and then Mix on API. Still hear a big difference?

Not sure what point you are making...?

AudioGaff, post: 300770 wrote: If you have had a lot of experience with great analog mixing, then you have that as a reference. If you have not had that, then your not even really qualifed to discuss it without at least having shared some kind of frame of reference.

No need for that. I am entitled to ask you to back up your claims even if I've never used a Neve or an API.

As it happens I think I do have experience with great analog mixers; they generally had the name Midas at the top.

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Jeemy Fri, 02/26/2010 - 02:26

quote: some equivalent, summed, across the mean?

i.e. its not 16x3dB exactly (or anywhere close), but each channel has a variance of between 0 and +/- 3 and the total variance is not exactly 3dB but some contributed value-per-channel.

just to clarify that one. thanks for the explanation on what you meant by linear, i was wondering about linear frequency responses from system to system, not that.

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AudioGaff Wed, 02/10/2010 - 23:31

I agree that there is merit with analog summing. But to do it right is expensive. Summing boxes are one method. If I am going that far then I lean more toward a decent analog console to do summing and all the other things a good console has and does. I have been digital mixing for the last year now, and miss analog but love the power, flexability and work flow of digital. To see if I really like it or can tolerate it, I sold some unused outboard and MIDI synths and got a Tascam DM4800 with options. Now with over 100 inputs, every single one being used, I have a DAW controller, 32-ch audio interface, digital mixing that does not have the same summing results that I hear from ITB, I can still mix ITB if I choose, I get to use the DSP of the Tascam for anything going through it, 24-mic pre's (ok, nothing to brag about but they are quite useable, and good enough for my outboard), a patchbay to interface all my really necessary outboard, analog and digital and I was able to get rid of 4-48 point patchbays.

It's a pretty sweet setup. But like any audio interface product used with any DAW software, you still have dick around with computer & software issues. I still prefer analog consoles but I am getting used to digital. Things run pretty good, but I have pretty high expectations. I can usally put up with the computer stuff when mixing. I also have a HD24 (also used for reliable remote recording) that can interface to the Tascam via ADAT if I want just record or mix old school.

If I commit to digital mixing, and I am just about there. I'd be eagarly wanting something like SSL digital or Euphonix console, but for my current home studio I will likely upgrade to something like the Yamaha DM2000 and use it with Nuendo or Cubase where the digital mixer and software are better fine tuned in working with one another.

Long story summary: Consider a decent digital mixer as an alternative to ITB or analog summing, and consider all the other things/features that it can provide.

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Boswell Fri, 02/26/2010 - 04:35

IIRs, post: 300742 wrote: I'm not actually sure that we are disagreeing about anything, except perhaps:

Logically: how would you know which mix was which? (assuming someone else mixed them of course!) And have you ever tested yourself?

I think it should be possible to do the test properly, if a little laborious: you would need to first create the mix using your summing box gains and pans (so that your mix desicions could be influenced by any analog gain staging non-linearities), then solo each of your stems, bus them internally as well as routing them to the individual outputs, and use meters to match levels and pan positions to the desired level of accuracy. If you have a DAW that lets you type in parameter values directly you should be able to match these to within 0.1dB fairly easily.

Of course, all modulation effects would need to be printed first, so that playback was identical for every pass.

This got me thinking: if you were running 16 analog outs as 8 stereo stems, that is indeed 8 different noise floor instead of 1. They would all be uncorrelated (I think?) and would therefore each add 3dB to the overall noise floor. So 7*3=21db extra converter noise from this setup. Have I got the maths right...? :confused:

Not quite sure what you mean by that. care to elaborate?

The point is that I believe the same mix engineer mixing the same tracks ITB (digital) and by external (analog) summing would end up with two different-sounding results. One mix would not necessarily better than the other, but there would be audible differences. The tenor of this thread is that there is therefore an implicit and unexplained difference between summing digitally and summing externally in analog.

If you could capture the exact settings used for the analog mix and reproduce them in the digital mix, the differences should disappear. So maybe we should be looking at why the engineer would arrive at different mixes and see if we can re-work the user interface that governs DAW mixes to give it more of the feel of an external mix.

I would agree with your noise figures if we were talking about white noise, but D-A converter noise has other content such as code-dependent conversion errors and components from the power supply. I don't think it is possible to state accurate figures for this effect, simply to note that the mix noise floor will rise in the order of 3dB per input channel.

By the way, no-one in this topic so far has mentioned one common reason for performing external analog summing: sample-rate conversion. It was how I got into using external summing. I had 96KHz tracks from which I needed 44.1KHz CDs, and the digital SRCs that I had available sounded horrible. It was a breath of fresh air to mix in analog tracks with a 40KHz bandwidth and then re-sample two-track at 44.1KHz. A lot of the clarity I am sure could be put down to the elimination of contorted phase effects in the 15-20KHz range, but this is one way I know to achieve the sound of a "direct-to-stereo" CD from recorded tracks.

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