Same thought, (nobody responded); same time frame, (20 years ago). I think it's like FM--it's going to try to capture the strongest of the signals. If you try to amplify it to the point where the louder signal is clipping, you just make the "capture effect" worse. So filter it until your 12KHz signal is louder than the rest. Or, maybe the 567 isn't going to be your friend on this project. Barry >Seeing no other replies - I'll jump in here with >my limited experience with the LM567 some >18 to 20 years ago ... > >My expereince, in the use of LM567's to do TouchTone >decoding, was that the more you can do to get the tone >(or tone range) of interest as the stonger signal - the >better, the cleaner, the fewer false outputs the 567 >will show. > >Seeings how you're working to detect a 12 KHz tone (or >signal) - why not high-pass (starting at, say, 10 KHz) or >bandpass in the 12 KHz area? > >My solution to TT decoding was to precede each bank >of 567's (two tone ranges) with an appropriate low or >high pass op-amp filter. The 567's would then actually >'work' whereas before operation could not in any way >be guaranteed ... > >Jim > >----- Original Message ----- >From: "Pedro Drummond" >To: >Sent: Thursday, August 02, 2001 6:06 PM >Subject: [EE]: Amplify then filter ? > > >Sorry for the missing tag lead. Here it goes again: > >----------- > >Hello, Gods' oracle. > >One question: > >I will be using the 567 filter IC to separate 12kHz signals from regular >audio. The problem is that the 12kHz has a much lower amplitude. Should I >amplify and then insert the full audio mixture to the 567, or will it be >able to detect a much lower signal, at the right frequency ? > >Thanks in advance. > > >Pedro. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.