[4631] b5 - Summing Grouped Audio Tracks, Peak Meter off

invol · Post by **invol** » Tue Feb 03, 2009 5:54 am

When running a single -6 dBFS test tone through group master, Peak meter reads -6 dBFS. When running the same tone twice, it reads + .02, and shows clipping.

It should not clip and should read 0 dBFS.

Could be my test tones... but worth looking into.

Full Sweep -6.00 db, 44.1 kHz

Test tones were generated with Make A Test Tone by Audio Ease.

-B

Tarekith · Post by **Tarekith** » Tue Feb 03, 2009 6:11 am

Confirmed, master out seems to be 0.02 off in all cases. Not sure how important that is, but worth knowing I guess.

ilia · Post by **ilia** » Tue Feb 03, 2009 6:29 am

Ooh, the Pentium bug from '94 is back again...

invol · Post by **invol** » Tue Feb 03, 2009 7:03 am

I know this is not a super big deal, but is worth noting. It could point to something more serious.

Matthias · Post by **Matthias** » Tue Feb 03, 2009 1:40 pm

hi invol,

we calculate the amplitude from dB by 10^(ValueInDB/20) which results in 0.5012 for -6dB. when added again it sums up to 1.0024 which is then about 0.0208 dB. to get an amplitude of exactly 0.5 you must set the sliders to -6.0206 dB.

as far as I see everything is as it should be...

best wishes,
matthias

Tarekith · Post by **Tarekith** » Tue Feb 03, 2009 2:39 pm

Thanks MR. Wizard (Matthias)!

invol · Post by **invol** » Wed Feb 04, 2009 12:55 am

Great. Thanks for the info.

So you are calculating it as voltage (right?), and I was just assuming the Inverse Square Law, which is dB SPL... Doh!

Thanks!
Brian

ilia · Post by **ilia** » Wed Feb 04, 2009 1:07 am

mmm, however you calculate it, -6db comes out to a little over 0.5 in amplitude (or a little over 0.25 in power) ratio. just saying.

invol · Post by **invol** » Wed Feb 04, 2009 2:23 am

Looks like I need to brush up on my physics : )