From: Brooks Magee
My comments are:
I have some questions about recording & post-processing levels with digital equipment (yes – I read your levels article, but I still have specific questions).
Hello, Brooks… no problem.
Ok.. I’m using a Korg 168RC digital mixer with a 1212 I/O card (16-bit, 44khz) in a Macintosh . The mixer manual suggests setting the trims so incoming (A/D) levels peak at about -6 db (the ‘peak hold’ option makes this pretty easy). That’s fine, though I recently heard (from more than one source) that when using 16-bit, it’s best to get the levels as close to 0db as possible without going over…in order to get the best S/N ration (and ‘compete’ with the 24-bit take-over). I’m confused…
I think you’d need two arbiters of quality here:
1) an external, calibrated digital meter. Perhaps the Korg meters are not accurate and they want to protect themselves.
2) Listen closely for distortion as well. Perhaps the Korg’s internal analog gain structure is somewhat screwed up and internal headroom is exceeded BEFORE the A/D clips. I’ve seen so many strange things in my career that I wouldn’t rule that out. Well, Brooks, you’re the one who’s going to have to do that investigation. If you rule out #1 and #2 above, then by all means, peak close to 0 dB on the A/D meter and listen closely for clipping.
I’m led to believe that it’s best to have a few db’s ‘headroom’ in your files to allow for all the number calculations that take place with mixing and/or adding effects. For example, I often process files through Waves plug-ins. The waves manual suggests setting the output level so the processed files peak between -6 and -4…if planning on using other waves/etc. plug-ins for that file. In case where I’m done with the plug-in processing for a file, the file will still be subject to calculations in my software (Deck) and/or Korg mixer later…plus I might need to make e.q. adjustments/tweaks for the clarity of the mix – all of which seems to boil down to more calculations to me (hence the need for ‘headroom’)…
Yes, in general this is true, and for 24 bit files, it’s not a loss.
So, what’s the real deal here? I notice a considerable loss of ‘punch’ and ‘presence’ in my individually processed tracks and my mixes/sub-mixes. How much headroom IS really necessary for my files – perhaps only 1db or less?
I strongly doubt that the lack of punch and presence has anything to do with your loss of headroom. I’ve recorded for many many years, and recorded level (within 10 dB or so) has nothing to do with “punch”. In other words, a good 24 bit A/D, peaking to -10 dBFS, listen to that output. Then peak to 0 dBFS, listen to that output. They should sound essentially identical, once you turn the monitor gain up to compensate. So, if you’re looking for “punch and presence”, look elsewhere for the problem…. It’s not a level thing.
Thanks in advance for your time. I know this subject has basically been covered on your site; I’m sorry I haven’t been able to figure out more difinitive answers myself.
In Grooviness,
B. Magee
Moongate Audio
I understand, Brooks, and your questions are coming from a good place and were not answered at the site. Hope this helps.
In grooviness, too,
Bob Katz