Topic: Distortion problem

[tchoub]

Hello,
I recently made a live recording with a pair of OKM II r microphones + A3 adpater and a D8.
The recording is totally distorded and I don't really understand why. It seems that the mics couldn't handle the bass present during the show...
Here are two samples :

• this one is from a quiet part of the show : slight distortion can be heard
• this one however is really distorded

Here are some infos about the recording :
 - levels under -12dB on the DAT
 - fresh battery in the A3
 - the A3 adpater (NO bass roll-off / NO attenuation) was plugged into the --line input-- of the DAT
 - recording knob at 3 on the DAT
 - mics placed in ears
 - located 10 meters back from the stacks
 - the show was not especially loud (I already recorded louder shows with Core Sound Binaural microphones without any distorsion)

I've read that cliping can occur with the D8 when the recording knob is under 4. Since the A3 adapter was plugged in the line in of the DAT, it can't be the cause of my problem. (?)
My opinion is that the distortion comes from the mics.

Can anyone familiar (or not) with this setup tell me if I'm correct about that ?
Besides, does anyone know what is the exact attenuation applied by the A3 adapter when the bass roll-off setting is used ?

Thanks !
 

[dnsacks]

on a d8, it's my understanding that any time the level knob needs to be turned below 4.5 in order to keep from getting digital overs, you're overloading the d8's op-amp and are brickwalling it/getting distortion.  Some inline attenuators should get you around this problem.

[hexyjones]

I'd say you should have had the attuenuator "on" on the A3...that's where the brickwalling is happening...

[Brian]

sounds like brickwalling.   try to keep your peaks in between -6 and 0 dB.  your tapes will sound better too....i guaruntee it

[hexyjones]

This might confirm my diagnosis........

http://www.soundman.de/englisch/prod_a3_eng.htm

Linear Attenuation

The switch position "-20dB" is used when recording high sound pressure levels. For moderate SPLs, especially with the A3 on the LINE input, the switch position "0" is recommended.

[tchoub]

thanks for your answers.
However, I'm quite confused.

I always thought that brickwalling meant "overloading the preamp of your deck".
So, is this "definition" not true ? Can a line input brickwall ?

I am quite sure that using the -20dB pad of the A3 could have helped but I don't know how it works.
Does it reduce the signal coming into the A3 or the one leaving the A3 ?
If it reduces the output signal of the A3, I can't see how it would prevent brickwalling a --line input--   

[hexyjones]

thanks for your answers.
However, I'm quite confused.

I always thought that brickwalling meant "overloading the preamp of your deck".
So, is this "definition" not true ? Can a line input brickwall ?

I am quite sure that using the -20dB pad of the A3 could have helped but I don't know how it works.
Does it reduce the signal coming into the A3 or the one leaving the A3 ?
If it reduces the output signal of the A3, I can't see how it would prevent brickwalling a --line input--   

I think "Brickwalling" is what happens when the waveform runs out of "space" and hits an upper limit and flattens out...becomes square and thus distortion...it can happen anywhere in a given signal path...mic or line...

Your signal is brickwalling before you even get the the "control" part of the circuit...thus the need for the attenuator...to knock it down a bit and make it manageable...It's the A3 that is brickwalling  - not the DAT...the attenuator will reduce the output from the mic...before it hits the pre...

[tchoub]

thanks for your answers.
However, I'm quite confused.

I always thought that brickwalling meant "overloading the preamp of your deck".
So, is this "definition" not true ? Can a line input brickwall ?

I am quite sure that using the -20dB pad of the A3 could have helped but I don't know how it works.
Does it reduce the signal coming into the A3 or the one leaving the A3 ?
If it reduces the output signal of the A3, I can't see how it would prevent brickwalling a --line input--   

I think "Brickwalling" is what happens when the waveform runs out of "space" and hits an upper limit and flattens out...becomes square and thus distortion...it can happen anywhere in a given signal path...mic or line...

Your signal is brickwalling before you even get the the "control" part of the circuit...thus the need for the attenuator...to knock it down a bit and make it manageable...It's the A3 that is brickwalling  - not the DAT...the attenuator will reduce the output from the mic...before it hits the pre...

ah, ok. Now I understand. So, it's the A3 that is the cause of the distortion and not the DAT. I agree with that.
If the attenuation pad on the A3 reduces the input signal of the A3, then it makes sense to use it to avoid brickwalling.
thanks ! 

[tchoub]

50 posts...
now I can +T you all. Thanks for your answers !