Electronics (alt.electronics)

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old March 24th 16, 04:56 PM posted to alt.electronics
external usenet poster
 
First recorded activity by DIYBanter: Mar 2016
Posts: 1
Default Audio 100V signal to line level

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

  #2   Report Post  
Old March 26th 16, 05:14 PM posted to alt.electronics
external usenet poster
 
First recorded activity by DIYBanter: Apr 2015
Posts: 116
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

  #3   Report Post  
Old March 28th 16, 02:58 PM posted to alt.electronics
external usenet poster
 
First recorded activity by DIYBanter: Jun 2010
Posts: 93
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

  #4   Report Post  
Old April 8th 16, 09:09 PM posted to alt.electronics
external usenet poster
 
First recorded activity by DIYBanter: Oct 2010
Posts: 1,405
Default Audio 100V signal to line level



"M Philbrook" wrote in message
...
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.


That's mainly about next stage input capacitance shunting the treble.

Doesn't take a lot of input capacitance for Xc to be low relative to the
dropper end of the network.

With 100V coming in, I'd put some resistance in series with that small
capacitor so the treble notes don't overload the input.

If there's any suspicion of the next stage being a bit fragile - clamp
diodes aren't too much of an extragance.



Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Very Odd Audio Common Mode Condition Started Just Before Midnight 12/31--Audio Feedback Oscillation through Power Line? Mark & Mary Ann Weiss Electronics 1 January 2nd 08 04:56 AM
need to convert from MIC level to LINE-INPUT level wylbur37 Electronics Repair 15 May 24th 07 04:45 AM
Combine two line level audio signals? Noozer Electronics 3 February 11th 07 07:05 AM
Unbal. Line-level to Bal. Mic-level M.Joshi Electronics Repair 5 July 31st 06 06:20 PM
THD claims of audio signal generators mc Electronics Repair 113 January 16th 06 02:52 AM


All times are GMT +1. The time now is 02:52 PM.

Powered by vBulletin® Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"

 

Copyright © 2017