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Gear / Technical Help => Post-Processing, Computer / Streaming / Internet Devices & Related Activity => Topic started by: Kyle on November 08, 2004, 04:18:13 PM

Title: SF7 DC offset
Post by: Kyle on November 08, 2004, 04:18:13 PM

I posted a question about SF7 and got a great answer but...
I recently saw a text file for a Phish show (do not remember whoch one) and it indicated that the recording was done with SF4.5 but the DC offset was removed from the entire show? So, I am back to the beginning - calibrate DC offset or not - please help - pulled a recent Mule show (and Hornsby) that must be transferred!

Thanks all!!

Kyle

Title: Re: SF7 DC offset
Post by: MattD on November 08, 2004, 04:33:33 PM

Well, here's one take on it:
http://www.bu.edu/webcentral/learning/av2/optimize-dcoffset.html

Title: Re: SF7 DC offset
Post by: Kyle on November 08, 2004, 04:39:07 PM

Thanks for the resource page - very nice!

So, to make sure I have this right..

Record first, the calibrate for DC offset

Let me know if I have got it

Kyle

Title: Re: SF7 DC offset
Post by: Brian Skalinder on November 08, 2004, 04:52:22 PM

You don't always need to correct DC offest - you only need to do it if there's an offset in the first place.  So, taking a step back:  what ADC are you using that creates the offset?

Title: Re: SF7 DC offset
Post by: Kyle on November 08, 2004, 04:55:38 PM

I am not even sure if there is one - I am new to DAT->computer transfers and I just want to do it right. Basically, I am taking my DATs (from shows) and transferring  S/PDIF in via the Audiophile 2496. My rig is mk4->v2->ad1000 so that is my ADC. Thanks for the info and please keep it coming!!!

Kyle

Title: Re: SF7 DC offset
Post by: Kyle on November 08, 2004, 07:03:35 PM

I did some recording

Using the DC offset correction in the Processes tab changed the appearance of the waveform, but I can't hear any differences between the scanned/unscanned version. Any suggestions?

Title: Re: SF7 DC offset
Post by: MattD on November 08, 2004, 09:29:10 PM

You probably won't be able to hear it. The harmonics it introduces are 2nd order and hard to hear, at least until you try to perform some processing. Your amp will also be happier when playing back :)

Title: Re: SF7 DC offset
Post by: ford prefect on December 17, 2004, 06:31:37 PM

If you're doing DAT > WAV transfers, first step before any processing (resample, normalize etc...) should be to remove the DC offset.  First Scan - If it finds one, remove it before the processing.  As I understand it, since processing is always performing mathematical algorithms on your sound files (on a computer) having a DC Offset is like having a centerline that moves.  Like this:

--------____________---------------------_____________

If you perform processing on a centerline that looks like that, you might get some more audible anomalies.  Note, it isn't as simple as the above example, but that analogy will hopefully help you understand why you want to get rid of it.

-Brad

Title: Re: SF7 DC offset
Post by: F.O.Bean on December 17, 2004, 06:50:53 PM

kyle, i did it on a few recordings and honestly i think it only needs to be done on older ecordings

i say go w/ out it unless there is a huge DC offset