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petrus bitbyter[_2_] petrus bitbyter[_2_] is offline
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Default Audio 100V signal to line level



schreef in bericht
...

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

Something seems to oscillate...

As mentioned already, speakers (with or without transformers) are partly
inductive loads. As the amplifier will be designed to anticipate for it, a
pure resistive load may cause the problem. So adding inductors may help.

Connecting a line to ground may cause a ground loop which in turn may cause
the oscillation. Replacing the low-value resistor by a small 1:1 transformer
may work.

petrus bitbyter