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anonymous 18 April 2002

Any D8b users ever check the amount of DC offset at the AES or SPDIF outputs? I recently did and its a lot! Here's the test: Most of us have the Apogee clock card and three Dig I/O installed and run vr. 3.0 Unplug all mic & line cabling as well as dig I/O cabling to cards. Set all faders to unity turn off all EQ,Comp,Gate and assign to the 2-bus.
I was SPDIF into wavelab @24 bit 44.1 via Card Deluxe I/O with Wavelab's input meters at standard setting. I use balanced power and run Ardsync wrd clk. Why do I see level? So I record what should be nothing and do a freq analysis and thar she blows! A brick wall of 20hz and that's where the lo freq on the graph begins. Who knows what's below that?
Upon calling the Mackoids on this, they said turn off the channel filters. This seemed to work but then turning only 1 ch of the "British EQ" hi-pass ( the best freq-ing one!) Boom, back to the DC offset. Shouldn't employing hi-pass help to eliminate super-low DC?
I checked a D8b at a dealer and same story. Mackie has no fix for me yet but is settting up the same test once Pat gets Wavelab in. Any experience on this might get me mixing again.

Thanks
Ron

Comments

Guest Fri, 04/19/2002 - 03:13

Pro Tools has an AudioSuite plug in 'DC offset" to remove this, perhaps ignore it then treat your mixes in PT for final mastering and DC offset removal.. :)

I know it can irratate MP3 converters.. I bet plenty of DATs make it to mastering with DC offset without folks knowing...

What a PITA

:mad:

knightfly Fri, 04/19/2002 - 09:20

"I will give you $5 if you can actually 'hear it' as opposed to 'see it' !"

Correct me if I'm wrong (happened once back in '65... :=)) but doesn't DC offset, by it's very nature, decrease headroom? So, wouldn't you be likely to hear it in the form of clipping, assuming you're keeping levels reasonably hot? Or, if you're listening but not looking at waveforms, you would automatically decrease levels when you heard the distortion, and maybe never know why you had poor S/N... Steve

Scott Gould Fri, 04/19/2002 - 11:39

Knightfly -
That is correct if you're talking analog signals, but I believe the poster was referring to the digital output - a stream of ones and zeros. I don't think headroom per se would be affected, but it might introduce jitter, digital clipping (which should be really, really obvious) or data corruption. I haven't heard any evidence of these on my d8b, but maybe I just got lucky. I'd be interested to hear more about the effects of DC offset on digital signals, as my knowledge rather rudimentary. Feel free to set me straight if I'm out in left field here. :D

Scott

pan Fri, 04/19/2002 - 17:24

Well here, Julian!

"I will give you $5 if you can actually 'hear it' as opposed to 'see it' !"

-->Do an edit of 2 mixes, one with and the other mix without DC-offset - no short fades possible!

Other Example: I (still) use a lovely Click-Sound kind of synth-cowbell-sample I imported from DAT few years ago...when I examined the Sound, I did DC-offset removal, but after doing that, the click did not sound the same anymore - the hard attack was gone - I bet another 5 EURO, that certainly most Analog Synthesizers gain their uniqe character by slight DC-Offset of the oscillators!

If in London, I definitely pop by to pick up the bet, what's 5$ in Pound, btw?

Cheers, Niko

pan Sat, 04/20/2002 - 05:42

knightfly wrote

Damn, sprained my ankle again jumping to conclusions - he did say AES and SPDIF, cranius rectumus strikes again! Well, no more drinks for the dwarf... Steve

Sorry, I was just hot for the bucks :D

Here's my conclusion for DC offset in digital transfers:

DC certainly degrades your digital signal in terms of Jitter. DC moves the trigger-point of a pulse-wave (that's what AES/SPDIF consists of).

Cheers, Niko

....and if you call me "dwarf" again, I got to get my big brother in.

anonymous Sat, 04/20/2002 - 09:06

"perhaps ignore it then treat your mixes in PT for final mastering and DC offset removal..

The frequency is probably lower than 20hz and inaudible..

I will give you $5 if you can actually 'hear it' as opposed to 'see it' !"

Although I could use the 5 dollars and yes, I'm aware it would be easy to fool my clients, I got into pro audio for the challange of creating something beautiful with the tools my business can afford. I will stop at nothing to squeeze every little bit of sonic pleasure out of my mixes for my clients.
I have described a problem that I think all D8b uesrs have and should be concerned about. We all paid around $10,000.00 for a console that should not add anything to our mixes but the power to build great mixes and please our artists. Please, do my test for yourself and post some possible solutions for me.

Thanks
Ron Benner
http://www.dogwoodrecording.com

Opus2000 Sat, 04/20/2002 - 09:48

Ummm...I know I'm late into joining this game but here's a silly question....is that Wavelab 4.0 you are recording into? If Wavelab 3.0 then that would probably be the reason as WL 3.0 doesnt support 24bit entirely....WL 4.0 does tho...
Just thought I'd throw my $.02 in and add it to Steve's $5.00!! So know he'll owe you $5.02!!!
Opus :D

Guest Sat, 04/20/2002 - 14:56

".is that Wavelab 4.0 you are recording into? If Wavelab 3.0 then that would probably be the reason as WL 3.0 doesnt support 24bit entirely....WL 4.0 does tho..."

Wow! have we got some gear heads here or what! :)

This whole dollar / Euro thing is going to make the final split of the prize money VERY difficult!

:D

anonymous Sat, 04/20/2002 - 20:11

". I haven't heard any evidence of these on my d8b, but maybe I just got lucky. I'd be interested to hear more about the effects of DC offset on digital signals, as my knowledge rather rudimentary. Feel free to set me straight if I'm out in left field here.

I generally love the power of the automation but it tends to feel like a toy and I can deal with that but lo end producing jitter or DC offset does make for less headroom in your mix.

Simple
pissed yet?
Ron

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