Does anybody know?

[koka]

Im recording mono channell with microphone but wave is not symetrical from zero crossing.

What does it mean? Is it some phasecoherent problem or something else?

[Carl Kolchak]

That's a bit vague, but do you have "draw waveforms rectified" checked in the preferences? if so un-check it.

Or do you mean there is a DC offset?

[koka]

No I havent draw waveform rectified checked. I think it is DC ofset but why its happend.

Is it mabye of spdif input from Alpha channel?

Anybodie using this Preamp with some problem?

[bortraws]

Give us some more information so everyone here can hopefully help you a bit better.

What's the Digi hardware you are using and how is everything connected?
Do you also get teh offset when recording from a line input for instance?

[koka]

Im recording on HD 3 accell but using optical input from SSL Alpha channel. When I record from Analog input on 192 IO everything is Ok. I cant hear any sound problem but the wave look strange. Im just wander what protools try to tell me with this.

Thanks for all your replays.

[Avid]

moved from LE to TDM forum

[RobMacki]

From what you described it could be DC offset. But waveforms are not always perfectly symmetrical.

[Shawn Simpson]

It sounds like some sort of offset in the alpha channel. Have you tried the analog outputs of the alpha straight to the 192? I can't tell from your previous post, but if that looks ok, then it might just be something in the ADC of the SSL box. If you have any other digital input devices, do any of them exhibit this same problem? If not, I'd see about getting that puppy checked out. It may be something as simple as a reset of some sort if it's just a DC offset, but it's impossible to say from where I'm sitting.

Hope that helps...probably not though.

[ThomasPMusic]

record the analog out of protools running signal generator thru the alpha channel, and thru a protools bus simultaniously and compare the 2 waves. A nice sine wave should reveal problems...
brass instruments and really heavy guitar tones are off center sometimes.
tp

[frenchman]

Im recording mono channell with microphone but wave is not symetrical from zero crossing.

Hey folks ! really, where did you get that notion that audio should be symmetrical ?

Asymmetrical waveform is a fact of life, notably in instuments that blow air, i.e. vocals, sax, trumpet etc.

This phenomena has been known for ages in the broadcast field on AM radio (try google words: asymmetrical waveform speech)

It must not be confused with offset due to DC present in the sigal fed to the A/D converter, or bad converter electronics (notably lo-fi computer soundcards...).
"Bad" offset usually shows in the waveform when the source is quiet.
My experience is that with proper interfaces and wiring, it is very rare as most peripherals have capacitors in series with the signal and various DC rejection circuitry.