Concern over quality loss during editing/mastering

[musicdavid]

I have recorded my album completely on analogue tape and have mixed it to DAT. I am now at the mastering stage and it is being done on a computer using the '4-inch' program.

There are a few edits I would like to make to the final mixes (pre-mastering), but I find that this is done far easier in software such as Cubase. (The mastering software doesn't seem to be designed to do things like editing in a precise way.)

What I've done before is to transfer the DAT mix onto my PC, done the edit in Cubase, 'mixed' this down and then copied it onto a CD to open it in the mastering software which is being done on the computer belonging to the person doing the mastering.

I'm concerned about data loss during this process. Especially as you then have to transfer the mastered versions on to another CD for the pressing plant. That's quite a few generations of copies for the ones on which editing has been carried out. I can't remember exactly what bit-rates I used during the various stages in the process described above, but I am sure this is a vital element in preserving quality.

What should I do to ensure maximum quality through this process?

 

[LogicDeLuxe]

If you can, record your mixer output directly through a reasonable soundcard in 24 bit quality. For example, Terratec or M-Audio have good cards for little money.

If this is no option, you have to convert your recording anyways since native DAT is 48000 Hz while CD audio is 44100 Hz (which is probably not as bad as it might sound with any sophisticated software, so you shouldn't worry about it too much.). Do a digital copy from your DAT to your PC and convert it to float before doing anything else. Then you can edit and master anything you want without loss. The final step is the conversion to 16 bit, 44100 Hz with appropriate noise shaping.

 

[SouthSIDE Glen]

The biggest bottleneck is in the mixing to DAT stage; not so much because of the sample rate (most of the more recent DAT models are switchable between 44.1k and 48k) but rather the 16-bit depth, which limits you to a usable 90dB signal-to-noise ratio. Also (again, depending upon make and model) not all DAT machines are exactly known for their stellar-sounding A/D converters.

I'd recommend something like Logic says and record directly to computer at 24-bits minimum, going through a halfway decent interface with a full 24-bit converter. Then you can do all your editing and prematering in Cuebase at 24 bits or better.

Wait to downsample to 16-bits until you are actually ready to burn, using a quality dither on the downsample.

IMHO ETC

G.

 

[SonicAlbert]

Since you recorded onto DAT, your bit rate is most likely 16. Even if you recorded it into Cubase at 24 bits, the 8 extra bits will be empty since the original data is 16.

If all you did in Cubase is edit, no processing, then you probably haven't added anything to those upper bits. But in any case, let the mastering house do any dithering or bit reduction. They will be more experienced and probably have better software or hardware for it.

I personally would have mixed from analog tape to the computer and avoided the DAT stage entirely. Unless your DAT machine has been regularly maintained and serviced, you could be getting very high error rates and not know it. Even error rates that are inaudible do affect the audio in subtle but negative ways.

Of course, you should have a good soundcard if you record directly to disc. But most good quality sound cards out there nowadays will sound as good or better than any DAT machine ever built. And they won't be expensive.

 

[musicdavid]

Thanks for your replies.

Firstly, I have already made mixes I'm happy with onto DAT so remixing on to the PC is not an option.

From what you're saying it looks like I should do the following:

• Transfer the mix onto the PC as 16 bit (24 bit is unnecessary, right?) as float - what is float and how do you do this?
  
• Do the editing and mixdown again at 16 bit.
  
• Copy onto CD as 16 bit to give to the mastering person.
  
• He should then save his mastered versions as 16 bit to burn to the master CD.

Please alter any of the above as you see fit!

 

[Ford Van]

If all you did in Cubase is edit, no processing, then you probably haven't added anything to those upper bits. But in any case, let the mastering house do any dithering or bit reduction. They will be more experienced and probably have better software or hardware for it.

Actually, at every crossfade there will be an increase of the bit depth needed to represent the new "mixed" audio.

Thanks for your replies.

Firstly, I have already made mixes I'm happy with onto DAT so remixing on to the PC is not an option.

From what you're saying it looks like I should do the following:

• Transfer the mix onto the PC as 16 bit (24 bit is unnecessary, right?) as float - what is float and how do you do this?
  
• Do the editing and mixdown again at 16 bit.
  
• Copy onto CD as 16 bit to give to the mastering person.
  
• He should then save his mastered versions as 16 bit to burn to the master CD.

Please alter any of the above as you see fit!

No, you should transfer the mixes from DAT tape onto the PC at the highest bit depth you can, and do this as a digital transfer! Indeed, since they are 16 bit, the LSB's (least significant bits) will just be zero's, but you will need it later..

Do the editing, but leave the audio at the high bit depth, at least 24 bit, 32 bit floating point would work too.

Copy onto CD as a DATA CD to give to the mastering person. DO NOT make a Audio CD. There are numerous good reasons not to and I don't have the time today to explain any of them. But make sure you make a DATA CD with .wav or .aif files on it.

Let him do his thing.

Really, you should just take your DAT tapes to the mastering engineer and let him do everything for you. Pay to watch the process and you will learn a lot.

 

[SouthSIDE Glen]

Transfer the mix onto the PC as 16 bit (24 bit is unnecessary, right?) as float - what is float and how do you do this?

"Float" refers to 32-bit floating point, which is really an enhanced version of 24-bit that provides a bit more accuracy and a bit more flexibility.

Albert is right that dumping to your PC at 24 bit in and of itself will not add any quality or resolution to the sound coming off your DAT, but there is potential advantage in working at 24-bit or better once on your PC and beyond to mastering I'd personally record it to 24-bit or better on your PC so you can take full advantage of the 24 bits when processing your mixes. 32-bit float is fine if your software has that option, and if the plugs your using operate all the way through at 32 bit float, but (IMHO YMMV) I think it's a bigger step to get up to 24 than it is to step from 24 to 32.

Do the editing and mixdown again at 16 bit.

I'd recommend doing your editing and premaster mixes in the computer at 24 bit (or better).

Copy onto CD as 16 bit to give to the mastering person.

If you are sending it to a real ME and not a Sears ME, you'd probably be better off (again, like Al alluded to) sending him a 24-bit file on a data CD rather than a 16-bit audio CD, and let them downsample and dither it to 16 bit for mastering.

[*]He should then save his mastered versions as 16 bit to burn to the master CD.

Correct. Chances are that his gear and software - particularly his dithering algorithms and his monitoring environment - are going to be better equipped for that part of the process than what you have.

EDIT: Oops, I got stuck on the phone as I was typing this reply and didn't see Ford sneak in there in the meantime with essentailly the same answers. Sorry, Ed, not trying to step on your toes or anything

G.

 

[Reggie]

4-inch program? What the devil is that?

Anyway, if you truly are giving this to a mastering engineer, I would check with them as far as what format they want. If they are legit, they should be able to work with whatever your best version is, and in this case it is your original DAT mixdown without any further monkeying around on your part.

If you are doing this yourself, I would transfer digitally via SPDIF into your computer in the same format the DAT was recorded in, then bring that into a 24bit or 32bit floating point session. And....outta time to type the rest of my thought...

 

[musicdavid]

4-inch program? What the devil is that?

Anyway, if you truly are giving this to a mastering engineer, I would check with them as far as what format they want. If they are legit, they should be able to work with whatever your best version is, and in this case it is your original DAT mixdown without any further monkeying around on your part.

If you are doing this yourself, I would transfer digitally via SPDIF into your computer in the same format the DAT was recorded in, then bring that into a 24bit or 32bit floating point session. And....outta time to type the rest of my thought...

Sorry, the program is called 'half-inch' I think, not 4-inch!

The reason why I need to transfer the mixes to my PC first is to make edits that are done far easier and more accurately in Cubase.

 

[Reggie]

In that case, I guess I would maybe open up a new 24bit Cubase session at whatever your DAT sample rate is (it will be either 48K or 44.1K), transfer from DAT to computer via SPDIF, do your edits in Cubase, export as a 24bit wav file at the same sample rate again, then burn the files onto a CD-R as data (not as an audio/music CD). As long as you keep the proper sample rate throughout, it should all be pretty straightforward, and there is no worry about copy generations as long as you use a decent burner with a decent CD-R at a decent speed (no more than 16X).