Hello,
I'm looking for a good solution to prevent RF and GSM detection with my amplifier, I now it could be done by filtering the input.
The input is a basic differential pair as on the following file :
http://www.diyaudio.com/forums/attachment.php?s=&postid=488146
ps: there is no more DC offset ...
Any advice is welcome.
David
I'm looking for a good solution to prevent RF and GSM detection with my amplifier, I now it could be done by filtering the input.
The input is a basic differential pair as on the following file :
http://www.diyaudio.com/forums/attachment.php?s=&postid=488146
ps: there is no more DC offset ...
Any advice is welcome.
David
The problem is that RF can get in anywhere - not just on the input. Also the wires to the speaker are excellent antennas for RF. So if you have a problem with RF you can try the old trick, which is to do one winding round a ferrite core ring or using one of these: . . .wel . . . please do a search on Farnell using this search word "535886". Then you will get the picture
Ohterwise you can make an input filter. I recommend using 1 MHz as cutoff, so you will not interfere with the audio signal too much - fase and amplitude wise.
Ohterwise you can make an input filter. I recommend using 1 MHz as cutoff, so you will not interfere with the audio signal too much - fase and amplitude wise.
You need to add R2 and C1 to your input stage:
http://users.ece.gatech.edu/~mleach/lowtim/instage.html
R2 - 2K
C1 - 390 pF mica (Arco DM15-391J or DigiKey 338-1057-ND
A ceramic cap may be used if nothing else is available.
http://users.ece.gatech.edu/~mleach/lowtim/instage.html
R2 - 2K
C1 - 390 pF mica (Arco DM15-391J or DigiKey 338-1057-ND
A ceramic cap may be used if nothing else is available.
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