SignalTools PPM issues

[Dan Lyth]

At our post-production facility we've found that the PPM metering offered by SignalTools is reading quite significantly lower with quick transients than when using PPM metering on Chromatec hardware meters. This could obviously result in tech review failures if relied upon for dubbing.
We're suprised this is the case and we were wondering if Digidesign had the meters approved from the BBC before releasing them?

Dan

[DigiTechSupt]

From what I can see, this has been logged as a bug and is being looked into.

[Soundworks UK]

Well, we've been testing it here and it's reacting EXACTLY the same as our DK Audio MSD600M++ on BBC scale........which is fed digitally from a 192.

[Mike Thornton]

Sad person that I am, I have a PT session with the appropriate burst tone tests that test the dynamic signal performance for the BBC PPM. So I ran a series of tests with the PPMulator VST plug-in with FXpansions VST to RTAS wrapper and the Digideign SignalTools meter on the BBC preset.


All tests done with a 10kHz sine wave at +8dBu (PPM6) as per the spec. Undertaken on a Dual 1.42Gig G4 with Pro Tools 7.1 software with HD2Accel and 192 interface.


burst duration - 100ms spec +8dBu tolerance +-0.5dB
PPMulator +7.5dB
SignalTools +7.5dB

burst duration - 10ms spec +6dBu tolerance +-0.5dB
PPMulator +6.0dB
SignalTools +3.0dB

burst duration - 5ms spec +4dBu tolerance +-0.75dB
PPMulator +4.5dB
SignalTools -0.5dB

burst duration - 1.5ms spec -1dBu tolerance +-1.0dB
PPMulator -2.0dB
SignalTools -9.0dB

burst duration - 0.5ms spec -9dBu tolerance +-2.0dB
PPMulator -10dB
SignalTools -13dB


So you can see from this data that the SignalTools PPM definitely doesn't meet the BBC or EBU spec for a PPM but the PPMulator plug-in does!


Hope that helps,