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Author Topic: I need to get rid of some brass distortion...  (Read 2481 times)

Thomas W. Bethel

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I need to get rid of some brass distortion...
« on: January 01, 2013, 07:09:53 pm »

I am trying to master a recording I did of a Chorus, organ and brass ensemble. There is some distortion on the right channel. I have gotten rid of most of the distortion until the brass ensemble and organ goes to a FFFF for the end of the piece. The level is way below 0dBFS and I cannot see any real distortion on the waveform but I can hear it. I have gotten rid of most of it with RX. Any other ideas or suggestions would be most appreciated. Thanks in advance.
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Thomas W. Bethel
Managing Director
Acoustik Musik, Ltd.
http://www.acoustikmusik.com/

Doing what you love is freedom.
Loving what you do is happiness.

Celebrating 26 years in business in 2021

Thomas W. Bethel

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Re: I need to get rid of some brass distortion...
« Reply #1 on: January 06, 2013, 07:33:22 am »

I finally figured out that I was never going to be able to get rid of all the distortion, so I used some creative editing.  I copied the left channel and replaced the right channel with the left channel making the track mono. I added some reverb and eq and it sounds pretty convincing.

Sometimes the simplest solution is the one that works...

FWIW
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Thomas W. Bethel
Managing Director
Acoustik Musik, Ltd.
http://www.acoustikmusik.com/

Doing what you love is freedom.
Loving what you do is happiness.

Celebrating 26 years in business in 2021

Jim Williams

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Re: I need to get rid of some brass distortion...
« Reply #2 on: January 06, 2013, 01:22:27 pm »

There are microphones that will cause distorion at certain frequencies, before the actual clipping point for a wideband signal.
If the mic's response is not flat, any "bump" will clip before the other frequencies will. This is very common on LDC's with "presence peaks", those will clip first.

Same applies to mic preamps, many designs will show rising THD with either levels or frequency. I found it best to have a THD curve that is flat 20~20k hz and no rise in distortion products until full clipping is reached. Keep in mind this is not fashionable with audio designers at this time. THD is "in".

Even so, clipping also has differences. Most all transistor gear will show "hard clipping", a square wave. That is very noticable in recordings. Some advanced designs will do what I call "extended amplitude bending", the curves won't hard clip across but bend upwards, a rounded overload curve instead of a flat line across the top of the waveform. It looks more like tube distortion and it is also  heavy on the pleasant sounding even harmonics vs the hard sounding odd harmonics of typical transistor clipping. I'm able to get that response using transconductance amplifier technology, but that's not normally found in pro audio.

Best to know the limitations of the gear you select. Use mics with an excess of operational headroom along with linear preamps and always be conservative with levels with 24 bit recordings.
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Thomas W. Bethel

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Re: I need to get rid of some brass distortion...
« Reply #3 on: January 07, 2013, 06:47:39 am »

There are microphones that will cause distorion at certain frequencies, before the actual clipping point for a wideband signal.
If the mic's response is not flat, any "bump" will clip before the other frequencies will. This is very common on LDC's with "presence peaks", those will clip first.

Same applies to mic preamps, many designs will show rising THD with either levels or frequency. I found it best to have a THD curve that is flat 20~20k hz and no rise in distortion products until full clipping is reached. Keep in mind this is not fashionable with audio designers at this time. THD is "in".

Even so, clipping also has differences. Most all transistor gear will show "hard clipping", a square wave. That is very noticable in recordings. Some advanced designs will do what I call "extended amplitude bending", the curves won't hard clip across but bend upwards, a rounded overload curve instead of a flat line across the top of the waveform. It looks more like tube distortion and it is also  heavy on the pleasant sounding even harmonics vs the hard sounding odd harmonics of typical transistor clipping. I'm able to get that response using transconductance amplifier technology, but that's not normally found in pro audio.

Best to know the limitations of the gear you select. Use mics with an excess of operational headroom along with linear preamps and always be conservative with levels with 24 bit recordings.

Thanks for the information.

I was using AKG Blue Line Cardioids C391-B in an X-Y configuration, two Audio Technica 4051s in Omni as flanker microphones, an Allen and Heath ZED-14 audio console and left myself a 12 dBFS headroom. I guess the brass just got away from itself. I used this same configuration to do the Canton Symphony a few weeks earlier when they performed Gustav Mahler - Symphony No. 2 in c minor ("Resurrection")  and everything worked fine and as you probably know that is a very dynamic piece to say the least. The only place where I got distortion on the recording in question was at the very last 5 seconds of a piece that was for Organ, Brass Ensemble and Chorus.

Again thanks for the response.

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Thomas W. Bethel
Managing Director
Acoustik Musik, Ltd.
http://www.acoustikmusik.com/

Doing what you love is freedom.
Loving what you do is happiness.

Celebrating 26 years in business in 2021

Jim Williams

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Re: I need to get rid of some brass distortion...
« Reply #4 on: January 07, 2013, 11:36:15 am »

The Blue lines have a rep for spittyness in the tops. The 4051 has a stepped response, a shelf like lift at 2k hz that really bothered me when I used them once. Otherwise they sounded pretty clear.
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