There are many reasons that will lead to clicks and pops when switching audio signals. You need to isolate the source of the problem. From what you describe it sounds like you have some kind of audio source that gets switched on to the analog input of the amplifier. In many cases the input to the amplifier is AC coupled. If there are any leakage currents in the system that allow the coupling cap to charge up then when the input is turned on the cap discharges causing the click. A simple solution to this is to provide a DC path to ground on the switch side of the cap. A high value resistor, 100K, will likely work if this is the source of the problem. Tom Dagostino Teraspeed Labs 13610 SW Harness Lane Beaverton, OR 97008 503-430-1065 http://www.teraspeed.com tom@xxxxxxxxxxxxx Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 401-284-1827 Teraspeed is the registered service mark of Teraspeed Consulting Group LLC -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Robert Sefton Sent: Saturday, February 12, 2005 9:37 AM To: adeelmk@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Switch On & Switch Off Clicks due to Amplifier noise Adeel - What is the source of the sound you're playing back? If it's coming out of an audio DAC and you're playing a stored audio clip through the DAC, then your problem may be at the DAC input. I've seen circuits like this where the input to the DAC is binary 0 before the track, transitions sharply at the start of the clip (the first click you hear), then transitions sharply back to 0 at the end of the track (the second click). Just take a close look at these starting and ending transitions. If the input to the DAC is unsigned, then "audio zero" whould be mid-range (e.g., 0x8000 for 16-bit samples), not 0x0000. Whatever the case, if you're feeding audio clips into a DAC you need to smooth out the DAC input. Consider it a crude digital anti-aliasing filter. Good luck, Bob S. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Adeel Malik Sent: Saturday, February 12, 2005 2:38 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Switch On & Switch Off Clicks due to Amplifier noise Hi All, In my application I am using a Stereo quality Audio Amplifier (TDA 7057A - Philips) for Sound Playback. I have kept the analog supply of amplifier isolated from the rest of the system along with the addition of high frequency by-pass capacitors as specified by the vendor. When I switch on the sound, a noticeable 'click' is heard before the playing of the message. The same 'click' is also heard after the sound playback. I suspect that this may be due to some amplifier phenomenon. Have someone experienced this issue before while designing with audio amplifiers.?. If yes, then how to resolve it ?. Thanks and Regards, Adeel Malik ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu