Re: Recording Steinway grand piano - damper noise
Posted: Thu Nov 14, 2019 10:06 am
Arpangel wrote:But have you checked it for DC offset? it can turn what you thought was an excellent Grammy award winning masterpiece into a worthless piece of plastic.
Just to be clear... The recording of Satie's piano toons is a very good one indeed. The DC offset is just a minor technical fault which won't affect anyone's enjoyment of the music in any way. I was just very surprised to spot it as it's such a rarity these days!
I've got The Box Hugh, would that show DC offset the same as the display you have, as a shift in image?
Nope, because it's an analogue meter.
The DC offset is something which affects the digital audio signal because the A-D converter is allocating the wrong quantising values to the audio signals. It's not audible in itself, although it can affect other signal processes and become audible in that way -- such as asymmetrical clipping etc.
You can think of it as the digital equivalent of a magnetised tape head on an analogue tape recorder. It also causes similar issues when editing -- clicks at butt edits -- and can lead to other problems with all kinds of signal processing, especially dynamics, and lead to inaccurate metering. These are all things that should have been obvious at the editing and mastering stages, and dealt with...
To spot DC offsets you either need a digital meter like the DK Technologies one I use, or a bit meter like the one that comes with RME's interfaces -- or their equivalents.
DC removal was built-in as an automatic process in a lot of mastering DAWs and processors back in the 90s... it's essentially just a high-pass filter with a very low turnover (1 to 5 Hz, typically) and a very steep slope.