Best way to eliminate turn-on thump

fiat79 · 10th February 2010, 12:50 AM

Planning my LM3886 chipamp and I understand I may run into turn-on thump. I won't be using a preamp per se, instead, I'll be running my squeezebox into a Marchand XM1 Crossover (kit) and then into my chipamp. Suggestions?

ryan750 · 10th February 2010, 02:46 AM

hi there,

It's written in the datasheet, using the mute pins. I got mine working and without turn on/off thump. You'll hear just a simple "tik" when your head is sticking directly on the speakers

thetube0a3 · 10th February 2010, 03:22 AM

I may be wrong but I seem to remember the chip not "un-muting" until power is stabilized all on its own? I thought that was mentioned in the data sheet.

I used very large caps a resistor to make mine fade in, So i never knew either way.

ratza · 10th February 2010, 04:23 AM

LM3886 doesn't have any thumps when switching the power on or off. Pay attention to the ground connections, use RF filters and you won't know if it's powered or not.

Redshift187 · 10th February 2010, 03:30 PM

Just use a mute circuit (like the one in the datasheet) and you won't hear much of anything.

thetube0a3 · 10th February 2010, 03:33 PM

Yea, with the large caps mine fades in pretty fast,almost instant. its so short you don't really notice it,

it seems like you hit the switch and have instant music, no pop, no thump.

ratza · 10th February 2010, 03:45 PM

I spent a lot of time to make my one dead silent. Now you cannot hear anything with the pot at maximum and input on the air.

fiat79 · 10th February 2010, 04:46 PM

Thanks guys - just wanted to make sure I was addressing any issues in the planning stages. I can't wait to get it built; I'm running a mid-fi Denon right now and I'm sure "it" can get better!

fiat79 · 11th February 2010, 12:57 PM

Also, the XM1 uses LF353 opamps with a 25k input impedance; is it better to use a 10k or 20k volume pot?

10th February 2010, 12:50 AM	#1
fiat79 diyAudio Member Join Date: Jul 2008	Best way to eliminate turn-on thump Planning my LM3886 chipamp and I understand I may run into turn-on thump. I won't be using a preamp per se, instead, I'll be running my squeezebox into a Marchand XM1 Crossover (kit) and then into my chipamp. Suggestions?

10th February 2010, 04:23 AM	#4
ratza diyAudio Member Join Date: Dec 2007 Location: Sibiu, Romania	LM3886 doesn't have any thumps when switching the power on or off. Pay attention to the ground connections, use RF filters and you won't know if it's powered or not. __________________ Any solution is a compromise.

10th February 2010, 03:30 PM	#5
Redshift187 diyAudio Member Join Date: Aug 2008	Just use a mute circuit (like the one in the datasheet) and you won't hear much of anything. __________________ Tyler

10th February 2010, 03:45 PM	#7
ratza diyAudio Member Join Date: Dec 2007 Location: Sibiu, Romania	I spent a lot of time to make my one dead silent. Now you cannot hear anything with the pot at maximum and input on the air. __________________ Any solution is a compromise.

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10th February 2010, 02:46 AM	#2
ryan750 diyAudio Member Join Date: Oct 2007	hi there, It's written in the datasheet, using the mute pins. I got mine working and without turn on/off thump. You'll hear just a simple "tik" when your head is sticking directly on the speakers

10th February 2010, 03:22 AM	#3
thetube0a3 diyAudio Member Join Date: May 2008	I may be wrong but I seem to remember the chip not "un-muting" until power is stabilized all on its own? I thought that was mentioned in the data sheet. I used very large caps a resistor to make mine fade in, So i never knew either way.

10th February 2010, 03:33 PM	#6
thetube0a3 diyAudio Member Join Date: May 2008	Yea, with the large caps mine fades in pretty fast,almost instant. its so short you don't really notice it, it seems like you hit the switch and have instant music, no pop, no thump.

10th February 2010, 04:46 PM	#8
fiat79 diyAudio Member Join Date: Jul 2008	Thanks guys - just wanted to make sure I was addressing any issues in the planning stages. I can't wait to get it built; I'm running a mid-fi Denon right now and I'm sure "it" can get better!

11th February 2010, 12:57 PM	#9
fiat79 diyAudio Member Join Date: Jul 2008	Also, the XM1 uses LF353 opamps with a 25k input impedance; is it better to use a 10k or 20k volume pot?

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