XTC and headroom....

rodos1979 · Post by **rodos1979** » Sun Jun 20, 2004 8:29 am

Hello to all!

I recently started to mix a lot with XTC and I was wondering about one thing. We all know that SFP/XTC are 32bit integer, which means that there is a limit of 192dB of headroom. That is the headroom that all CW mixers got. So, it IS possible to make your CW mixer digitally clip (unlike the SX mixer which is 32bit floating and doesnt clip).

So, I was wondering...ok...lets say that you take care and wherever you use an XTC plugin, the audio doesnt clip. But all the audio of all the XTC plugins is processed by your CW card, which has the limit of 192dB. How could one know that your CW card is not clipping, since there is no meter anywhere for that?

The same question applies to all DSP cards which use integer maths (TC for example)...

Just wondering... Does anybody know?

rodos1979 · Post by **rodos1979** » Tue Jun 22, 2004 4:14 pm

Am I asking a silly question? Or nobody knows!?

Astroman, At0mic, Garyb??

Post by **garyb** » Tue Jun 22, 2004 5:49 pm

i thought that it was the other way around, that 32bit integer had a greater dynamic range and that 32bit float was basically 24bit with 8bits of overflow.

either way, i don't think it's really an issue as there is really no audio stream, just processors doing calculations. if the host app is not clipped, i wouldn't expect any of the plugins which aren't clipping in themselves to cause the cards outputs to clip.

that said, i could be very wrong. it really doesn't matter however, as long as the product made with that hard/soft combination sounds good.....

rodos1979 · Post by **rodos1979** » Wed Jun 23, 2004 5:06 am

Thanks for replying Gary!

On 2004-06-22 18:49, garyb wrote:
i thought that it was the other way around, that 32bit integer had a greater dynamic range and that 32bit float was basically 24bit with 8bits of overflow.

It is true that 32bit integer has a greater dynamic range in comparison to 32bit float (192dB vs 144dB). But in 32bit integer the "limit is fixed" at 192dB when adding signals, while in 32bit float it is impossible to reach the limit!

either way, i don't think it's really an issue as there is really no audio stream, just processors doing calculations. if the host app is not clipped, i wouldn't expect any of the plugins which aren't clipping in themselves to cause the cards outputs to clip.

that said, i could be very wrong. it really doesn't matter however, as long as the product made with that hard/soft combination sounds good.....

True and well said.. The question got araised as I was working on a mix lately, and maxed the DSPs in XTC mode.. The CPU meter was around 50-60%, and had about 30-40 tracks and a couple of VSTi and many VST effects. There are one or two moments in the song where it sounds somewhat clipped but neither the Mix Out, nor any of the channels seem to clip... Still investigating...

Post by **garyb** » Wed Jun 23, 2004 2:29 pm

it's possible to clip both native and cw plugins....

rodos1979 · Post by **rodos1979** » Wed Jun 23, 2004 7:09 pm

Native 32bit float plugs cannot clip in theory.... In practice they MAY clip when your software converts 32bit flt mathematics into integer, which can clip.

Post by **hubird** » Wed Jun 23, 2004 10:19 pm