Continuing the 16bit Analog Input Debate....

[FrankH]

I was going to title this post as: "Save Yourself 8 Pages of Misinformation, Charts, Graphs and Acrimony" but it wouldn't fit.
I'm posting this as a separate thread to avoid 8 pages of confusion, misinformation, flawed testing and (eventually) uncalled-for acrimony.

I had a lengthy conversation this morning with the engineer who programmed the V3.1 fixes and the entire V5.x software revision. Not some low level guy. The top guy. The guy who would know. I have that kind of address book.

The subject of our conversation was the appearance of a 16bit signal being passed from the Mic/Line Pre to the digital outputs (Direct or 2Mix).

Let me start by how he prefaced his answer: by pointing out the theoretical dynamic range of 24 bits: it's 144dB.

What's the preamp's dynamic range spec of the D8B?
• Preamp dynamic range: 114 dB RMS max.

That said.....he continued:

The Cirrus A/D converter in the D8B is in fact, a 24bit converter. The original programming of V3.0 analog signal chain was brutally flawed. It passed a 16bit signal with an additional 8bits of a sort of "repeat" to form a 24bit word. This was corrected in V3.1 and further refined (to perfection, I am told) in V5.x.

So why the appearance of what looks to be a 16bit signal being passed from the Mic/Line>Direct/2Mix chain?

Plain and simple: the analog preamp's dynamic range. The D8B's preamp in front of the A/D doesn't have a large dynamic range. Keep in mind, this is a preamp using 1996 components producing a usable range of 60 dB feeding a converter developed somewhere around 1996.

What this means is the D8B can only take advantage of, on average, about 16-18bits when being fed a signal near the upper limit of the preamplifier. Really pushed? Maybe 20bits. He said that typically, the material filling up the last few bits is noise.

To compare, a signal being generated from a high end VSTi synth such as U-He's Diva can produce a full 24 bit signal in a DAW, pass it into the D8B, via Lightpipe, send it out at the Direct Out or 2 Mix Out and will (depending on the material) be measured as a full 24bit signal.

Plug a high end "boutique" A/D preamp into any of the D8B's digital inputs and it will produce a signal that is actually less than 24bits because the dynamic range still falls short of 144dB. Have a look at high end A/D preamps specs. Have a look at mid-line gear (RME, MOTU and the like) It's eye-opening. They are not producing full 24 bit words on average either. Just sayin'.

So, to sum up:

V3.0 software produces a 24bit signal with the first 16bit actually being the signal and the last 8 bits a sort of "repeat of the first 16 filler". It is essentially, a 16bit signal. It was "the dirty little secret". It is crap.

V3.1 software was debugged to produce a theoretically "real" 24 bit signal but doing so becomes limited by the dynamic range of the analog preamp. The process was improved but not perfectly.

V5.x software has additional tweaks over V3.1 to make this process as efficient as was theoretically possible within the constraints of the hardware elements (the preamp and A/D converter).

It's the analog preamp that's the bottleneck, not the converter. It really is a 24bit A/D converter in there.

P.S.: Version 5 is a lot more than a graphic overhaul. Plenty of useful new features and tons of bug fixes. It is well worth the upgrade fee.

[anyhorizon]

I don't wish to disagree with you Frank but the converters in the d8b are not Analog Devices chips, they are Cirrus. You are correct though in that they are 24 bit.

Peter

[FrankH]

they are Cirrus

True enough. CS 5360's (Since replaced by CS 5361's).

I forgot. It's been a while.

Originally (in development) we started with Analog Devices. Cirrus were cheaper....we went with that. They are indeed 24 bit converters.

Changed the text in my original post.

[BrianJ]

So...question is, can the preamps be changed for something more "pro" ??? If so, what would that be?

[anyhorizon]

So...question is, can the preamps be changed for something more "pro" ??? If so, what would that be?

Anything's possible but logistically, it would be a brave man who tackled the task. The components are all Surface Mount Devices (SMD) which, unless you're tooled up and tenacious, is a mighty tedious affair. You could possibly find superior ICs but you would most likely have to change some of the surrounding components and perhaps circuitry as well. This would be major. Not only that, the 12 internal mic pre-amps are no slouches for the money, especially now. The line amps are fine. You're better off getting a few high end external pres for the critical stuff and running with the internals for the less important stuff. I've changed a few resistors and caps on some of the boards and quite frankly, I'm more inclined to take a trip to the dentist and have a few teeth pulled than go down the mod road again.

Peter

[FrankH]

So...question is, can the preamps be changed for something more "pro" ??? If so, what would that be?

This subject was discussed here:
viewtopic.php?f=2&t=642

[High C Double G]

Hi everyone,

Thank you Frank, thank you very much for being here, contributing, and taking the time to make the call and report back to us!

I have been running this desk, for the most part, digitally so what is being said, if I am reading this right, is even with a digital in, it will output (through the desk after whatever DSP) less than 24-bits?

Sorry for the broken sentence, but you know me

I really have not one complaint on the sound of this unit, and it really makes no difference to me at all. It is just a curiosity thing for me - I thought I was riding the wave, hugging the curve (so to speak) by using mostly the digital I/O.

A long time friend (very good engineer), I think he is doing some sort of Foley mixing work at Sony or something... hey it's not a bad job, mentioned to me about the d8b (and he had one for a long time in the beginning until he got a Pro Tools HD rig from a super famous guy)... anyway he told me the d8b was about flexibility and to use all it had... the analogue, digital, Auxes, buss outs, everything. This is what the mixer excels at.

Anyway, thank you for the good info, and I am super tired now so I will re-read to see if what I read is what I thought I read... well I hope you know what I mean to say

Carry on, it is about the music after all.

High C
a.k.a Michael

[Dan Worley]

Great information, Frank! Thank you to you and your friend.

c-ya,

Dan Worley

[garrett21allen]

Hi everyone

I was waiting around to see where this was going. Im glade frank gave us that great information.
yall please don't get made at what Im going to say. everyone is talking about 16 bit and 24 bit
so I have more bits than all yall. I looked in my wallet today and I had 35 bits. and if gas goe's up any more
I want have them bits but a few days. thanks again frank

joe allen

[hyaena]

I´m glad the storm has gone and the waves are running high no more.

Jo Allen has even put the icing on the cake with 35 bits.
Even Peter H, our beloved host, has come back to the regular entrance codes aside the 16bit question.

Thanks, Frank, for keeping the focus on some hence unknown facts !
I´ll stick to the d8b anyhow.

Manfred