Capacitors on/across Speaker Out Terminals

1965GTO · 22nd April 2011, 09:55 PM

Hello,

What is the benefit of putting capacitors on the speaker out terminals? Is there one, why would they be there?

I caught this on a schematic. See attached.

sofaspud · 22nd April 2011, 10:27 PM

Is this the sort of thing recommended for RFI? Seems it's gotta be a high-frequency shunt of some kind. I don't think I've ever seen it on a schematic, though.

DigitalJunkie · 22nd April 2011, 11:46 PM

I've seen small caps,a couple hundred pF,on speaker outputs before. I assume it must be to suppress RFI.

jaycee · 23rd April 2011, 12:46 AM

They are RFI suppression. Sometimes they add a resistor too, and in this case it works as a Zobel network

martin clark · 23rd April 2011, 12:50 AM

Otherwise it's a really bad idea. Pure capacitance on the output of power amps does no good at all.

nigelwright7557 · 23rd April 2011, 12:51 AM

Zobel, emi or if class d a filter capacitor.

22nd April 2011, 10:27 PM	#2
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	Is this the sort of thing recommended for RFI? Seems it's gotta be a high-frequency shunt of some kind. I don't think I've ever seen it on a schematic, though. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

23rd April 2011, 12:51 AM	#6
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	Zobel, emi or if class d a filter capacitor. __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software.

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22nd April 2011, 11:46 PM	#3
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	I've seen small caps,a couple hundred pF,on speaker outputs before. I assume it must be to suppress RFI.

23rd April 2011, 12:46 AM	#4
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	They are RFI suppression. Sometimes they add a resistor too, and in this case it works as a Zobel network

23rd April 2011, 12:50 AM	#5
martin clark diyAudio Member Join Date: Jul 2003 Location: Bath, UK	Otherwise it's a really bad idea. Pure capacitance on the output of power amps does no good at all.

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