White Paper - The Pro Tools 48-bit Mixer

[Frank Kruse]

Lets say I have two master recordings in stereo. One was made on a 16bit DAW the other on PT 48bit. The masters are 24bit.
If in theory the two masters null out to digital zero when summed phase reverse, is there a chance that they still sound different through the same converters?

Background of this question is the fact that I have read arguements and statements about AS plug-ins sounding "worse" than the TDm equivalent. Some people insist on hearing a difference between those two files even when they totally null out in phase reverse sum. I think this is complete nonsense.

How can two files that contain the identical digital data sound different. It´s like alt-draging a sound to another track in PT and claiming that one sounds different than the other. Is it not?

frank.

[rockridge]

Digi is promoting their 48-bit mixer because there's been a trend towards analog summing... out to other equipment... not digi hardware.
Hear them say, "We can't have that; our customer's may discover other manufacturers!"

They're hoping that a 48-bit mixer will allow for a sound that approximates the red-lining bigness of analog summing without leaving the cage... i mean the box.

[Monte McGuire]

Lets say I have two master recordings in stereo. One was made on a 16bit DAW the other on PT 48bit. The masters are 24bit.
If in theory the two masters null out to digital zero when summed phase reverse, is there a chance that they still sound different through the same converters?

If the same clock is used, then I would not expect a difference. They better actually be the same data though, not just "close".

Background of this question is the fact that I have read arguements and statements about AS plug-ins sounding "worse" than the TDm equivalent. Some people insist on hearing a difference between those two files even when they totally null out in phase reverse sum. I think this is complete nonsense.

I wonder whether these two cases always null out. I just ran a simple test using a stereo overhead pair from a drum miking to test this. Using Waves 5 on my HD3 Accel system (PT6.9, 10.3.8), I put that audio on a track, inserted a Q4 plugin set to highpass and add two bands of HF boost. I copied the plugin settings and pasted them to an AudioSuite version of Q4. I created a new file using AudioSuite and then did a bounce to disk of the original file, processed through the TDM Q4 with the mixer set to 0dB fader, resulting in one set of files processed with AudioSuite (floating point) and another processed with TDM.

After importing the two sets of files, I time aligned them to compensate for the various delays and then inverted one pair using Trim (the other channel also got a Trim, set to not invert). Setting all the channel meters to peak reading, I found that the peak level of the sum was not null, it was pretty consistently 80dB below the peak level of each of the source channels with the plugin nowhere near clipping. They clearly don't null, and the error is 80dB down, not anywhere near -144 or something you'd expect from 24 bit processing.

Now, Q4 is not known for its cleanliness on TDM, but AFAIK, it's a 22 bit plugin. I was surprised to see the error at such a high level, nowhere near what 22 bits would imply.

I ran an additional test and bounced using the RTAS version of Q4. When nulled with the AudioSuite material, I got a null of -124.5dB, which is also what I get when I duplicate a track, invert it and sum it against the noninverted original. I assume this is either DC offset, the error from dither in the mixer and/or any shenanigans that Trim is doing to the signals.

I invite others to do this test using different plugins and differnet source material. You need no special tools other than the plugin, your audio and ProTools.

-monte-

[Alécio Costa]

So here we go with RTAs x TDM again.
I have seen some peple swear they would prefer the sound of the RTAS version of some plugs. A myth, right?
I remember Mr. Bob O. comenting at PSW (REP) that the RTAS focusrite EQ sounded better than the TDM version.
BTW.. Where is Nika?

[Logichead]

I will be more interested in mixing in-the-box when someone comes up with a way to emulate the goodness that analog consoles give. For the moment, an analog summing box is a good compromise. I have a Dangerous 2BusLT and have run identical mixes through it and a beautiful custom API. The API was slightly bigger and deeper sounding, also slightly darker and slower. The Dangerous was quicker and slightly leaner. I also use a Manley 16x2 mixer. All sound wonderful and inspiring to me, better than any itb work I have done.

I will try another itb mix, but what I have found in the past is the overal sound to be smaller, shallower, colder and harsher than using a console. If the differences are getting smaller, great. I am sure there are plenty of hits being mixed itb. There is also much that I hear that I think sounds terrible, mostly contemporary "hit" music. I am also sure that Bob Clearmoutain could do a better job mixing itb than I could on his SSL.

Glad to hear about the math going on - but I don't want a totally transparent sound. The next step is a way to tweak the 48-bit mixer into "misbehaving" in musically valuable ways. It's all distortion - but that's what I want!

I realise I could put a plug across the master, but I suspect that a new level of plug will be required to compete with analog. (Recently, I have been putting a Phoenix plug across all of the outputs on their way to the summing. This seems to be a bit more subtle than putting one across the master.)

Like it or not, digital doesn't yet compete with great analog pieces. I have every confidence they will - someday.

Best...H

[HiRaX]

I think my brain is bleeding

[Matti]

This 'White Paper - The Pro Tools 48-bit Mixer' is fascinating and gives much confidence in ProTools TDM. What about the LE mixer? How is it working?

Best regards

Matti Kontio

[SteveSZ]

Just to throw my 2 cents in,

To my ear it has always sounded like the greatest benefit from outboard "analog," tube, or classic devices has been at the input recording where the most significant shaping of an instrument's sound should be anyway.

The paper's very informative, I'm glad Digi put it out there. It's going to come in handy as I've got more than one client who likes to grill me like an onion whenever they hear someone say that they heard someone say that there's a magazine article where some famous engineer says that such and such a black box is the REAL way to record, mix, master or whatever.

That question a few posts ago about "what are good plug-ins": the answer is "the one's that make it sound the way you want to."

I say use your ears and your skills and bend the box to your will.

Thanks Digi

SteveSZ

[Touchwood Studios]

I've tried external mixing/summing and I get far more mileage (bang for the buck) out of using external comps and and Eq's than any summing that I have tried. I guess everyone has there "own way" - and that's the great thing about PT you can make it work for the way ***YOU*** want to work.

One stupid question:

Should I use "Stereo Mixer" or "Stereo Dithered Mixer" ??

Which one is better??