LM4780: is Cin optional?

akunec · 24th February 2005, 09:51 PM

I forgot to order Cin 1uF caps from digikey. I have other pp caps but only up to about 0.1uf. I also have some polarized electrolytic caps around 10uf. Could I use one of these caps instead?

Mr Teal · 25th February 2005, 02:50 AM

I'm a newb, so take what I say with a grain of salt, but lowering the value of the cap will lower your input cutoff freq. If you're not using the amp with a preamp that's DC coupled (ie, if your preamp already has a DC blocking cap at the output) you should be fine.

soundNERD · 25th February 2005, 03:13 AM

It seems like you can not use it, because all it does is prevent DC from getting to your speakers. Don't try the amp the first time with good speakers in case your source has any DC output. It also helps eliminate turn on/off thumps from your source (not the amp).

You can always go to a local electronic store. It may be a lot more money, but if its only one part, I think it's worth it to put it in.

24th February 2005, 09:51 PM	#1
akunec diyAudio Member Join Date: Aug 2004 Location: Alberta	LM4780: is Cin optional? I forgot to order Cin 1uF caps from digikey. I have other pp caps but only up to about 0.1uf. I also have some polarized electrolytic caps around 10uf. Could I use one of these caps instead?

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25th February 2005, 02:50 AM	#2
Mr Teal diyAudio Member Join Date: Nov 2003 Location: Saskatoon	I'm a newb, so take what I say with a grain of salt, but lowering the value of the cap will lower your input cutoff freq. If you're not using the amp with a preamp that's DC coupled (ie, if your preamp already has a DC blocking cap at the output) you should be fine.

25th February 2005, 03:13 AM	#3
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	It seems like you can not use it, because all it does is prevent DC from getting to your speakers. Don't try the amp the first time with good speakers in case your source has any DC output. It also helps eliminate turn on/off thumps from your source (not the amp). You can always go to a local electronic store. It may be a lot more money, but if its only one part, I think it's worth it to put it in.

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