Topic: Brickwall???

[yug du nord]

What does it sound like when the evil "brickwall" effect happens?  I know the wav file is squared-off (stick o' butter)...  but what sound occurs?  Is it just major distortion or something...  or is the music completely inaudible?  Something happened to me the other night and I'm tryin' to figure it out.

Thanks!

[J.D.S.]

brickwalling happens when your microphone's output are too hot for your preamp. or your pre can't handle the output of your mic's. you might need to get attenuater's if you're not running a pre/ad. if your mics have a attenuation pads that might help. to -10db's. I assume you might be running your pre levels high?   

[DSatz]

uncleyug, depending on the complexity of the sound that you start with and the severity of the distortion, "brickwalling" (hard clipping) can be inaudible or it can cause a very nasty type of distortion which can sound as if dynamic, wideband noise has been mixed into the music.

Attached is a brief sample of live music which I've transferred once "cleanly" and then repeated four times--each time increasing the clipping distortion, while keeping the overall average level nearly the same. This should help you hear the effect. There's a 500 KB limit on file attachments here, so I had to upload this as a relatively low bitrate mp3. The mp3 encoding makes the clipped waveforms less rectangular-looking if you load the file into editing software, but the audible effect is still very clear, I think.

Note that the distortion in the first of the distorted samples occurs only during brief, momentary peaks, and isn't terrible sounding. As the degree of clipping increases, however, not only are the peaks more and more severely squashed, but also the sound is being affected for a greater and greater proportion of the time (duration) of the musical excerpt. That's characteristic of hard clipping.

--best regards

[reverser]

Thanks DSatz!  Very helpful and educational as usual.

[ethan]

Nice sample +T

FWIW you can get the same sonic affect when a limiter is used.

The tops of the wave forms do not have to be square.

-e

[spyder9]

Any way of cleaning the brickwalling from the recording, using software like Adobe Audition? 

I just brickwalled for the first time ever last week.  Recorded the opening act fine.  Main act had the drummer's foot pedal piped into the PA and crushed me.  I hate that.

[dgale]

One thing that I know always used to cause confusion with folks who experienced brickwalling back in the DAT days was that they had set their levels right where they wanted them, watched them all night, and never had them exceed 0 db, so they were at a loss as to why it could have occurred.  In my experience with the Sony portable DATs, it was a case of overloading the deck's pre-amp, which occurred prior to the levels being set...it didn't matter how high or low you adjusted the levels on the deck, it was going to occur as the incoming signal was too hot for the deck's pre to handle.  One rule of thumb someone gave me back then that worked pretty good (at least with those decks), was that if you had to set the level knob below "4" to get the levels where you wanted them then your signal was probably too hot and you should turn down or attenuate the incoming signal enough to get it to the point the level knob was set >4.  Not sure how well that advice works with the new wave of HD recorders but it always worked well for me with the small DAT decks. 

[DSatz]

spyder9, yes--Adobe Audition has a surprisingly effective "Clip Restoration" feature under the Effects menu, strangely grouped as "Noise Reduction". It may take a little experimentation to find the best settings for a given recording. Try small amounts at first.

dgale, not only do the mike preamps in the little Sony DAT recorders overload easily, but the level meters, while "digital" in the sense of being segmented bar graphs, are driven by the deck's analog circuitry and are not true peak-reading meters. I have seen OVER indications when those meters were still reading -4 dB. The OVER indicators are digitally driven but they, too, do not always respond to signal peaks--it may take as many as three consecutive overloaded samples before they light up.

In general I regard the D-7 and D-8 as what people around here call "bit buckets" and I never use their analog circuitry or their metering.

--best regards (and welcome back, everybody!)

[spyder9]

spyder9, yes--Adobe Audition has a surprisingly effective "Clip Restoration" feature under the Effects menu, strangely grouped as "Noise Reduction". It may take a little experimentation to find the best settings for a given recording. Try small amounts at first.

dgale, not only do the mike preamps in the little Sony DAT recorders overload easily, but the level meters, while "digital" in the sense of being segmented bar graphs, are driven by the deck's analog circuitry and are not true peak-reading meters. I have seen OVER indications when those meters were still reading -4 dB. The OVER indicators are digitally driven but they, too, do not always respond to signal peaks--it may take as many as three consecutive overloaded samples before they light up.

In general I regard the D-7 and D-8 as what people around here call "bit buckets" and I never use their analog circuitry or their metering.

--best regards (and welcome back, everybody!)

+T.  Lets keep our fingers crossed.  I'll give it a shot this week.     

[spyder9]

Thanks O.  I've done the same tedious work with hand claps.  In this case, it will be the thunder of the foot pedal.  I hope this works.  This show is worth saving.  Its Santana - Albany, NY from last week.  Derek Trucks comes on stage for 3 songs.