Topic: Brickwalled recordings

[Ekib]

Some of my older recordings , like 1991-1992 etc. are brickwalled. I didn't use the -20 DB settings at every concert.
They're not really bad , most of the time they're listenable. It's just when there is a really high note ( like a guitarsolo ) you can hear it.
Now , is there a trick to get rid off this ? Is there some kind of software that can fix this ?

Thanks !

[boojum]

Samplitude offers a clipping plugin that can help some.  I am sure other editors can, too.  Audacity has more plugins than Carter has pills, so there must be one for this.  I'd check it out if I were you.  Audacity and the plugins are free.

[DSatz]

Adobe Audition also has a "de-clipping" feature that work fairly well with mild to moderate clipping (say, up to 3 - 4 dB). If you try to fix a recording that has 10 dB of clipping or more (i.e. the peak levels would have been 10 dB greater if they hadn't been clipped), the software's projections become less appropriate and the result sounds noisy and strange.

An old friend of mine once called this the "law of conservation of goodness." From experience it seems to be a general rule--if you can fix a minor problem with a small amount of processing, it's far more likely to succeed than trying to fix a major problem with a lot of processing.

[newplanet7]

What about brickwalling that occurs before the clipping threshold?
I was under the impression that clipping and brickwalling were two different entities.
Clipping is actually the preamps being overloaded and brickwalling was
the preamp overloading the ad stage thus no actual clipping (0db) has to be present.

My first time out I bricked and my levels were around -4 tops the whole time.
Am I misunderstanding this? 

[newplanet7]

^^^^^^^^^^^^^^^^^^^^^
Bueller.............. Bueller.............. Bueller...............

[DSatz]

Any time a signal runs into a hard limit, that's clipping. Regardless of what causes it, the term still applies.

"Brickwalling" is a term that I frankly never heard before I came to this forum. It's not in general use in professional audio; "clipping" is the term that everyone (outside of here) knows.

[Gutbucket]

Beat me to it..

Brickwalling, clipping.. same difference. You run out of headroom and the waveform is flattened at the peaks and troughs.  Around these parts people call it brickwalling when a previous stage clips hard somewhere before the meters.  In that case the levels on the meters look OK but the signal is already clipped before it gets to the ADC.  Some analog stages may distort more gently when they are slightly overloaded, squashing the waveform in a more gradual, rounded way. A small amount of that distortion can sometimes sound good, but they can also clip sharply as if hitting a proverbial brick wall, sounding ugly.  I've never heard the term brickwalling term outside of this forum.

[newplanet7]

Exactly what I was getting at.
I can "clip" at -4db where the waveform is boxed off at -4db.
Most people around here refer to clipping as "going over" 0 right?

Not too many people see clipping as anything but going over 0.
Thus the term brickwalling was born?
I am still confused.
I'd like to hear more people weigh in on this because
a lot of threads here treat it as two separate things.

My basic point being that clipping is in one part of the signal chain and brickwalling
is at a latter part of that signal chain
Thus both being different.
I guess My main question is how do you clip without coming close to "over"

[fmaderjr]

DSatz could explain the technicalities if he has time.

In practice, most (all?) of the recorders we use have a setting on the level control that if you need to turn the level below that point to keep the meters from going over 0 dB, you are likely to have brickwall distortion. If you learn this point for your recorder, you should never have a problem with brickwall distortion (as long as the sound pressure isn't more than your mics can handle). Instead of turning your levels below this point you can use a pad or a preamp capable of attenuation (like the ST-9100).

guysonic mentions some of these in the recorder reviews on his site.

Some of these points I've read about on this forum:
R-09             8
MZ-RH1        12
iHP-120       -0.5
Korg MR-1   -10
 

[Roving Sign]

Brickwalling is certain kind of clipping - referring specifically to the overload of the first input stage on any given recorder. No amount of gain adjustment will clean up the signal.

Example: The old Sony TCD5M Analog cassette field recorders had a -20db pad switch. You were guaranteed to distort(brickwall) the signal if you did not use this pad.

Clipping is more like when you set your levels too high and overdrive something downstream. (tape head/A>D converter)

[Roving Sign]

Beat me to it..

Brickwalling, clipping.. same difference. You run out of headroom and the waveform is flattened at the peaks and troughs.  Around these parts people call it brickwalling when a previous stage clips hard somewhere before the meters.  In that case the levels on the meters look OK but the signal is already clipped.

And to that point - Once you screw up a few times you can get an eye for meters that dont "look right"

You'll notice a distinct lack of bounce to your signal meters - only the top few bars will blink.

VU needles are more revealing...no swing. Just a trembling needle.

[newplanet7]

Thanks fellas.
It only happened to me one time/first time

[Gutbucket]

My basic point being that clipping is in one part of the signal chain and brickwalling
is at a latter part of that signal chain
Thus both being different.
I guess My main question is how do you clip without coming close to "over"

To rehash, Brickwalling is a provincial term only really used around here, but as used here you have it backwards.  It is clipping earlier in the signal chain than the point where the meters are monitoring. 

Because levels can be adjusted between stages it is possible to clip the input stage then have the signal level reduced to a manageable level before reaching the later stage where you are monitoring the meters.  Like Roving mentions, when this occurs you may notice that the level meter isn't 'bouncing' right, but just tops out at a certain point below full scale.  That's a subtle indication that the clipping is occurring earlier in the chain.  If there was a separate calibrated meter at that earlier stage, you would see it overloading, but by the time the signal gets to the final stage with the meters, the signal level is back under control.  The recorder is at that point faithfully recording an already clipped signal, regardless of where you set the final levels.

Instead of an all-in-one recorder, imagine a signal chain with separate components for each function: mics > mic preamp > ADC > digital recorder.  Imagine separate level adjustments at the mics (attenuating pad switch), preamp (gain) and ADC (gain/attenuation).  If there were also meters on each component, you could adjust everything so that each component was operating in a comfortable range.  Going though that process is called gain-staging and is an important part of setting up a studio recording chain.  In an all-in-one recorder all those separate boxes are in one device, and we rely on the manufacturer to optimize the gain-staging for us since they are condensing all that stuff into one device. 

[newplanet7]

  Because levels can be adjusted between stages it is possible to clip the input stage then have the signal level reduced to a manageable level before reaching the later stage where you are monitoring the meters.  Like Roving mentions, when this occurs you may notice that the level meter isn't 'bouncing' right, but just tops out at a certain point below full scale.  That's a subtle indication that the clipping is occurring earlier in the chain.  If there was a separate calibrated meter at that earlier stage, you would see it overloading, but by the time the signal gets to the final stage with the meters, the signal level is back under control.  The recorder is at that point faithfully recording an already clipped signal, regardless of where you set the final levels.

And there it is. 
That makes perfect sense.
Thanks gutbucket/roving.

[it-goes-to-eleven]

To rehash, Brickwalling is a provincial term only really used around here, but as used here you have it backwards.  It is clipping earlier in the signal chain than the point where the meters are monitoring. 

An example where it doesn't happen earlier in the chain is a case like the r09 being run at trim settings below 8.  It can brickwall without clipping, and before -6.