JB3 Level control - Analog gain or digital?

[hexyjones]

Just wondering how this control works...is it really analog gain...? or is it more like a digital gain increase like "Normalize"?

Anyone know...?

[dklein]

on line in, it's analog.  Proof here http://ca.geocities.com/dkleined@rogers.com/audio/JB3analog/JB3_Analog_recording.htm

[hexyjones]

mmm...well I may agree with his general conclusion...some of those obervations are a bit off...IMO...

Like his observations on the mic pre...well it's brickwalling...as I would expect the mic in on ANY portable (with no attenuation applied to the mic) - the rolloff could be an aritfact of the overload? I dont disagree that it is useless...but he seems to make some sort of mystery about what's happening...I doubt it has that kind rolloff built in...but it's pretty impossible to test unless we are recording whispers...

But again the last two paragraphs cut to the chaff...seems like it is analog gain...

[dklein]

fyi - the 'he' is me so I can probably respond directly (and I'm not insulted by a challenge).

There is no way the mic pre is brickwalling with a pair of CSBs mic'g a home system.  Their output is so low.  I ran the same SPLs at various mic and line gain settings and always observed the same effect.  At more moderate SPLs (without brickwalling the pre), the same high frequency attenuation is there on mic-in.

[hexyjones]

fyi - the 'he' is me so I can probably respond directly (and I'm not insulted by a challenge).

There is no way the mic pre is brickwalling with a pair of CSBs mic'g a home system.  Their output is so low.  I ran the same SPLs at various mic and line gain settings and always observed the same effect.  At more moderate SPLs (without brickwalling the pre), the same high frequency attenuation is there on mic-in.

The JB3 issue aside...

How are the CSBs designed to be run...? Are they setup to go into a line input or mic input...(not sure if there is a battery box involved?)

[dklein]

CSBs have a lower than typical output - they were designed to be used with the mic-inputs on the Sony DATs, which overloaded easily (and is why we have all heard of brickwalling).  I'm quite sure they are Linkwitz modified Panasonic capsules - the mod allows higher SPLs and more linear response than the stock config (like the Squids and many others).  It also drops the output levels, hence no preamp brickwalling.  There is a battery box - it's a standard design.  Rolloff is set for Sony DAT mic-input impedance (and does nada on line-in).

oh - btw, somebody else had speculated that the JB3 rolloff on mic-in had to do with it being primarily for voice recording, and that perhaps it was there so you don't hear the hard drive noise that bleeds into the recording when using high gain settings (remember mic-in goes to +48 dB).  Makes sense, although it's covering up one problem with another.

[hexyjones]

http://www.core-sound.com/mics.html#INTRODUCTION

When recording loud sound sources with your CSB microphones we recommend using your recorder's low sensitivity (-20 dB) setting.

Since there is no such setting on the JB3 mic in - I will remain unconvinced...in a nice +T way...

[dklein]

there is no such setting on the JB3 mic in - I will remain unconvinced...in a nice +T way...

ok fine.  I'll maintain that they are lower than typical but of course one must always consider the recorder.  Maybe the web page isn't clear.
same SPLs and mics, plugged into the JB3.
Recording #1 - mic in, 0 dB gain
Recording #2 - line in, 0 dB gain

Open the two up in a wave editor, rec #1 is flat sounding and 3 dB down from rec#2.  Both are below full scale.  If the mic pre were adding extra gain it would show up in the wave file.

In any case, I like your style, +t backatcha!

[hexyjones]

Here's the test the might help...

Try to run your CSB test with a Sony DAT with the attenuator "off" the mic in...ie set it too "high" sensitivity...approximating the condition that the JB3 sees...

Might not be as easy to duplicate because of the nature of the level control...(a 0db preset...?)

I'd like to see what that wave form looks like...

[hexyjones]

there is no such setting on the JB3 mic in - I will remain unconvinced...in a nice +T way...

ok fine.  I'll maintain that they are lower than typical but of course one must always consider the recorder.  Maybe the web page isn't clear.
same SPLs and mics, plugged into the JB3.
Recording #1 - mic in, 0 dB gain
Recording #2 - line in, 0 dB gain

Open the two up in a wave editor, rec #1 is flat sounding and 3 dB down from rec#2.  Both are below full scale.  If the mic pre were adding extra gain it would show up in the wave file.

In any case, I like your style, +t backatcha!

The fact that they are below scale doesnt matter...Im sure everyone has made a recording that the levels looked right but turned out to be a distorted mess...no matter how much of the available wavespace is used...

And it clearly states in the CSB page...to use the -20db...a condition we cannot create on the JB3

[dklein]

The fact that they are below scale doesnt matter...Im sure everyone has made a recording that the levels looked right but turned out to be a distorted mess...no matter how much of the available wavespace is used...

ah yes...but it does not exhibit the distortion of a brickwalled recording.  Forgot to mention that.  You are totally right that being below full scale is typical in a brickwall situation.

[hexyjones]

Define "exhibit" - you mean you dont hear any grungy or static noise...? I thought those flat tops on the wave were defacto distortion...square waves...

I think "distortion" can be more subtle than that...like low end sucking up all the headroom and making a recording or channel sound muffled...maybe...

[dklein]

ok...you've worn me out.  I don't have a DAT to play with.  I actually had to look back on the thread to remember what is was even about.  Our debate is a non relevant issue.
mic in sucks
line in is fine

At least we agree that the line-in gain is analog