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M Philbrook M Philbrook is offline
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Default Audio 100V signal to line level

In article ,
says...

All,

I am doing some testing with an audio PA system that has the output of 100V (rms). What I am trying to do is take this 100V(rms) and bring it down to an audio line level of about 280 mV (rms). I am doing this with a resistor divider.


1.) An image of 100V (rms) input signal measured on oscilloscope is below:


http://s1070.photobucket.com/user/Mr...bcqkm.jpg.html


2.) I am then dividing this down to ~280mV with a resistor divider,
375k and 1k. Here is the image of the signal from the resistor divider:


http://s1070.photobucket.com/user/Mr...6hhbp.jpg.html


As you can see the signal here looks extremely distorted on the oscilloscope! I am not sure if this is what really is happening or if it is an artifact of the oscilloscope.


3.) We have some audio equipment from the company Audio Precision here and with their equipment the signal looks much cleaner. See image below:

http://s1070.photobucket.com/user/Mr...9km9s.jpg.html


4.) There are some transformer options out there to take a 100V signal and bring it to a line level but I wanted to see if we could do this with a less expensive resistor divider solution.

Thank you from any thoughts you have on this.

-Robert


you have what looks to me like parasitic RF being introduced in your
network.

Not knowing how your termination are being made is a big issue, too.

in the old days, and still today that is, we use parasitic chokes.
Those are carbon composite low value R's wrapped with a few turns of
magnetic wire and each end attached to the leg of the R. This inturn
captures RF on the surface and shorts it via the R, while passing
through the orginal signal.

Another note. don't use inductive type Rs

You could put a small cap across the network.

Jamie