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-   -   Clipping Indicator (http://www.diyaudio.com/forums/chip-amps/54808-clipping-indicator.html)

scott_jcp 5th April 2005 09:08 AM

Clipping Indicator
 
I want to add a clipping indicator to my Gainclone.

I found a schematic at http://www.sound.westhost.com/project23.htm, but I have a few questions.

1) The text seems to indicate I can input another amp at A to monitor multiple amps at once. I would like to do this, seeing as my amp is stereo, but how do I connect the + and - outputs of the second amp at A?

2) What are the 3 resistors, cap, and diode connected to at the bottom right?

3) When he says the opamp +Ve pins are connected to the 12V Zener, what exactly does that mean with respect to the wiring?

macboy 5th April 2005 02:25 PM

First off, I would strongly recommend project 57 instead. It works by actually detecting the distortion created by clipping. But I'll also answer your questions:

1. You see that lonely diode at the bottom, connected on only one side with the other side labelled "A"? Well, that's for (one of) the other amps that you connect. You can see the corresponding diode for the first channel directly above it. You need to build the first half of the circuit (everything up to and including U1A) once for each amp that you want to connect, but each of those connects to this same point, each through it's own diode.

2. U1B and all that stuff hanging off of it creates a peak hold detector. Basically it makes sure that a very brief pulse at the input (indicating the amp clipping very briefly) is stretched out in time long enough for you to see the LED clipping indicator. If the LED was to only light exactly when the amp was clipping, you wouldn't even notice it until you were clipping really badly.

3. The opamp(s) postive supply pin (+Ve) will connect to the cathode end of the zener. The zener (with resistor labelled "see table 1") is acting as a shunt regulator to create a 12 V power supply for the opamps.

Giaime 5th April 2005 02:27 PM

1) I think that you must duplicate the whole circuit before of the A point to connect something to that point. I mean the two trannies, the first opamp section... The text is just saying that the only thing you couldn't do is to use the same circuit for different power supplies...

2) Do you mean the 1uF cap and 100k resistor? I think that they are used to "stretch" the clip pulse to light the led for a longer interval, just because it would be too short to see.

3) The writer is not clear about that; refer to the schematic on top of the page for wiring.

Hope this helps...

Edit: oh, I just saw another one who explained better...


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