How to judge A/D conversion quality. What specs?

[RecordingMaster]

Hi there,

I currently have a Tascam US-1800 USB 2.0 interface. It has 4 line level jacks on the back (w/ no preamps), 8 XLR inputs with digital pres and 2 Di inputs. I usually use my outboard pre's to feed to the line level jacks, and then use the left over xlr's for the rest of my mics when recording a larger instrument (like drums or a detailed guitar setup with multiple mics).

Thing is, so I've read, and so I am hearing, the A/D conversion quality on the us-1800 is not considered to be anything magical whatsoever. I find the stock digital XLR pre's thin and lackluster. While my outboard pre's sound better, they are still passing through this not-so-pro A/D converter which in essence is sort of robbing the potential of what my outboard can do.

That being said, I came across a used MOTU 896 Firewire interface for sale for $200 CAD (the original - 10 yrs old or so). I figured that was a good deal (bargaining to occur of course) and my first thought was that surely thing must have, not only better A/D conversion, but also better XLR pre-amps. They are analog preamps on the front when using the mic or line switch, but they are combo jacks and you can flip the switch to bypass the pre amps (for outboard), so win win!

Instead of just ASSUMING the A/D will be better on this thing compared to my Tascam, how can I know for sure, aside from just "using my ears". Surely there has got to be a something on paper that says how good an a/d converter is, or else why would people buy the great ones if it only CLAIMS to be great? I need something reinforcing my assumption of the a/d conversion, instead of just buying it and trying. As that would be a rather silly decision to make based on purely assumption.

So I am asking you, not just "what do you THINK about the a/d conversion in the motu 896 compared to tascam us-1800", but also "what do you KNOW about the differences in quality of either converter"? lol

Any help is greatly appreciated! Thanks.

 

[miroslav]

All converters will have specs that you can compare....BUT....it often does come down to which one YOU think sounds better.

You can run some Internet searches about a given converter(s) and see what the consensus is, but even at the pro level, everyone is using something different...there is no *one* brand/model that is agreed as far superior to all others...etc....so again, it comes down to personal preferences (and budgets).

I also think that putting the bulk of the "quality" burden on the conversion...is not very valid. Preamps, yes...there's more there to notice...but with conversion, you REALLY have to listen and hear the most subtle differences to pick one over another.

 

[Ethan Winer]

I've read, and so I am hearing, the A/D conversion quality on the us-1800 is not considered to be anything magical whatsoever.

Audio itself is a science, so there's no room for magic. Leave that for the musicians, and the sound designers and mixing engineers.

Surely there has got to be a something on paper that says how good an a/d converter is

Of course - it's called specifications. Not all gear makers offer complete specs. In fact, most gear specs are inadequate. But specs still can tell you everything needed about fidelity. This article describes the basic specs in plain English:

Audiophoolery

This is equally relevant:

Perception - the Final Frontier

--Ethan

 

[dgatwood]

My general attitude is that the difference in converters, once you get past the cheap crap that only does 48 kHz and under, is so small that you are unlikely to be able to hear it in even the most ideal conditions. Preamps make a big difference, microphones doubly so, mic positioning triply so.

But if you really insist on focusing on a component that probably isn't contributing to your problem at all, look for low THD (e.g. 0.0007%), large negative EIN numbers (e.g. -129 dBu), and a flat, wide passband (frequency response) through then entire human hearing range. Most of the problems you're likely to find are in the area of noise, particularly high frequency brittleness caused by having crappy components in the audio path. I would expect those problems to be readily detected in the form of crappy EIN and crappy THD.

 

[Mo Facta]

With your ears? Specs mean very little.

Comparing AD converters can be easy if you're using a single DA as the universal handicap. Just make identical recordings of a single source with each converter for playback.

For DA converters, the only way to really know is to A/B them at the same perceived loudness. Switching between converters within the ears' aural memory time frame can be a challenge, too. Especially if they only use Firewire or USB. In that case you'll need two computers and a switching system. Mission.

There were converters that beat Apogee converter specs for a long time yet they still sounded better. Why? Better filter implementation. Better analog components. Better overall design.

The subjective nature of what "'sounds better" is not easily measurable.

FWIW, I always found MOTU converters to be quite cloudy and not really that much better than other prosumer stuff. My Lynx and Apogee converters, on the other hand, were instantly perceived as better sounding as was the DA of my Dangerous D-Box. Yes, I A/Bed them all, along with Yamaha and RME converters off of a console.

YMMV.

Cheers

 

[mjbphotos]

I'd think that any A/D converters 10 years old are probably inferior just because of the advancement of technology since then.