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  #1  
Old 03-04-2002, 04:35 AM
jackruston jackruston is offline
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Default Problem with Dizzy\'s soft clip function

Hi
I dont know if this is an issue or a fault with my unit, but I'm hoping someone from engineering can help me out.

When the soft clipping function is engaged on the 192 interface there is audible nasty distortion even when meter levels are a few db off zero.

I bought a compressor at the same time as the 192 interface and inserted it across the master fader. I noticed this distortion and called the guy who made the compressor. I thought it might have been a valve problem or something. It turns out that turning off the soft clipping solved the problem. I wouldnt actually have wanted them on for that application normally anyway, but today I was tracking guitars through an ISA430, and they had a nasty fizzy distorion again. Level was peaking at about -5. Turned off the soft clipper on that input and problem solved.

Why oh why?

Thanks for any advice

Jack
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  #2  
Old 03-04-2002, 06:49 AM
ngisedigid ngisedigid is offline
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Default Re: Problem with Dizzy\'s soft clip function

Jack,

I encountered a similar issue on violin and piano tracks. Unfortunately, it was a live performance and little I could do.

Is Dizzy tinny with soft clip on?

I hope I am missing something, otherwise, I see no use for soft clip.
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  #3  
Old 03-04-2002, 07:10 AM
jackruston jackruston is offline
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Default Re: Problem with Dizzy\'s soft clip function

I didnt think it was tinny when it wasnt distorting but it's definitely a tinny distortion if you see what I mean. Glad it's not just me. If that is the sound the soft clipper is supposed to make...
J
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  #4  
Old 03-04-2002, 08:09 AM
jackruston jackruston is offline
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Default Re: Problem with Dizzy\'s soft clip function

I cant believe it's meant to do this. A soft clip function is surely supposed to prevent nasty distortions rather than cause them...I had assumed that it would effectively create more headroom not less. However I could be doing something stupid. Could it be affected by whether the signals are -10 or +4. Perhaps I have somehow set the hardware up wrong. Help digi help!
Jack
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  #5  
Old 03-04-2002, 09:23 AM
JLD JLD is offline
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Default Re: Problem with Dizzy\'s soft clip function

May be there is a way to adjust the soft clipping threshold as you can do in the Apogee AD8000.
It will perhaps solve the problem? [img]images/icons/wink.gif[/img]
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  #6  
Old 03-04-2002, 09:32 AM
ngisedigid ngisedigid is offline
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Default Re: Problem with Dizzy\'s soft clip function

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by jackruston:
I didnt think it was tinny when it wasnt distorting but it's definitely a tinny distortion if you see what I mean. ...
J
<HR></BLOCKQUOTE>

I did not mean to imply that the 192 is always tinny with soft clip -- I experienced the tinny sound only at the loudest stanzas, but within what should have been "proper" recording levels with quality mics and neutral mic pre's.
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  #7  
Old 03-04-2002, 09:35 AM
jackruston jackruston is offline
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Default Re: Problem with Dizzy\'s soft clip function

Okay, thats exactly what I have too. I'm sorry your session got screwed up. I can imagine it will be very tricky to fix, if it can be done.
J
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  #8  
Old 03-04-2002, 10:27 AM
D Clementson D Clementson is offline
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Default Re: Problem with Dizzy\'s soft clip function

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by jackruston:

When the soft clipping function is engaged on the 192 interface there is audible nasty distortion even when meter levels are a few db off zero.
<HR></BLOCKQUOTE>

The soft clipper starts modifying the waveform at about -5dBFS. It rounds the tops of the waveform to the extent that 0dBFS is reached at a level that would correspond to +4 dBFS if the limiter were not engaged (and the ADC would not clip, which it obviously it would).

I've never heard anything "fuzzy' in the distortion, though. I'll check into it and report back.

DC
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  #9  
Old 03-04-2002, 04:38 PM
D Clementson D Clementson is offline
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Default Re: Problem with Dizzy\'s soft clip function

I got a brand new 192 I/O from stock, and hooked it up. I used the signal generator plugin to create a 0 dBFS sinewave, routed it out the 192, then looped it back into the 192 via an external mic pre for some analog gain (a Millenia HV-3D that was handy, if that matters). I recorded the analog input with the soft clipper ON and examined the waveform. Everything looked fine: a sinewave with rounded top and bottom. It sounded just like you'd expect it to - a tone with harmonics. Then I used a piano track instead of the generator, and it also sounded like you'd expect: a piano with the tops rounded off of its peaks in the loud passages.

In playing with it, though, I think I may have discovered a clue about the original complaint. When the clipper is engaged, it was just about impossible to set levels properly. You almost can't drive the ADC to 0dBFS, so it is relatively easy to WAY overdrive the 192 input, clipping the input circuits in the process. All the metering points are downstream from the clipper, so you don't have any way to tell if you're overloading the inputs. Input overload produces a most nasty sound, and I'm guessing that's what Jack heard originally.

Remember, the clipper gives only about 4 dB of headroom "expansion." Overdriving by any more than that causes you run the risk of overloading the circuitry upstream of the clipper. This is dependent on the calibration of the unit, too. You just have to watch out that you don't exceed the overall maximum input level of +27 dBu.

Jack, is it possible that that's what you were seeing?

DC
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  #10  
Old 03-04-2002, 06:04 PM
ngisedigid ngisedigid is offline
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Default Re: Problem with Dizzy\'s soft clip function

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by D Clementson:
When the clipper is engaged, it was just about impossible to set levels properly. You almost can't drive the ADC to 0dBFS, so it is relatively easy to WAY overdrive the 192 input, clipping the input circuits in the process. All the metering points are downstream from the clipper, so you don't have any way to tell if you're overloading the inputs. Input overload produces a most nasty sound...
DC
<HR></BLOCKQUOTE>

Is the practical solution to set mic pre levels with soft clip off; then turn soft clip on before recording? Are the LED's perhaps upstream of the clipper? Is there a software fix? Other than ignoring the on screen meters and led meters on the box, is a properly calibrated mixing board the only option? I haven't found anything on this issue in the manuals. Have I missed it?

Dave, your help is much appreciated.
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