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[DPRG] Blab Buster in Feb. Nuts & Volts

Subject: [DPRG] Blab Buster in Feb. Nuts & Volts
From: R. Bickle rbickle at swbell.net
Date: Fri Feb 8 11:28:30 CST 2002


I have seen some circuits for this on the web called a "compander". They
were large agglomerations of op-amp circuits to limit the volume. I'm not a
bit analog guy, but I did find a device on the net for cheap that does the

Here's the link:

Of course, this won't work with digital inputs, but TV and Satellite sound
signals are not digital anyway right? (Assuming you're not getting
commercials on DVD.)


-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org]On Behalf
Of Jeff Koenig
Sent: Friday, February 08, 2002 8:59 AM
To: DPRG List
Subject: Re: [DPRG] Blab Buster in Feb. Nuts & Volts

Hi Dennis,

I think the circuit you are looking for is called a "compressor" in the
guitar (and maybe audio) trade.  Unless I'm mis-remembering it, a compressor
tries to make the volume constant.

If you want to tackle making a unity-gain amplifier that goes between your
amplifier and your speakers, you might look into National Semiconductor's
LM12 part.  It is a 150W general purpose amplifier that can be used for
servo or audio applications.  I have a sample somewhere, but I understand
that they are not inexpensive.

If your amplifier has one of those goofy motorized potentiometers for volume
(as mine does), I don't think the loop response will be very fast...


-----Original Message-----
>From: Dennis Draheim <dennis.draheim at attbi.com>
To: DPRG List <dprglist at dprg.org>
Date: Thursday, February 07, 2002 7:03 PM
Subject: [DPRG] Blab Buster in Feb. Nuts & Volts

>Hey guys,
>Just read an interesting article on how to build an automatic level control
>for audio signals.  The Blab Buster sits between an analog audio source and
>your amplifier, and boosts the low volume signals and clips the high volume
>signals, which is just what I need when I want to watch TV while the
>unit is sleeping in the next room.  Unfortunately, some of my audio sources
>are now digital, which makes it impractical to put this device before the
>amp.  I was wondering what it would take to build a similar circuit between
>the amp and the speakers, so that it would work no matter what the audio
>source was.  I'm just not sure whether it would be possible to do this
>without major power electronics (100W/channel amp).
>Now to make this relevant to this group:  Maybe a good way to do this would
>be to have a device that turns up or down the volume knob on my amp to
>maintain the voltage to the speakers (or the ambient noise level of the
>room?) within a certain range?  Not sure if the response would be as fast
>I'd like, though.
>Anybody done anything like this before?
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