How to spilt one channel out from stereo for woofer

chchyong89 · 23rd April 2009, 01:48 PM

Hi, i am new to here, i have a quite stupid question to ask, suppose i have a gainclone stereo amplifier with two LM3886, how i can split out and modify to install another mono LM3886 to sound up a subwoofer speaker. An easy way to say is, to make it 2.0 to 2.1.. can you guys show me any schmatics for me

thanks

regards

Dxvideo · 23rd April 2009, 02:51 PM

Just add 10K resistors to each channels line level output, then connect their other pins together. And from this junction put another 10K to the gorund.. Means make a Y shape with 10K resistors.. One branch to left channel, one branch to right channel and one to ground..
Then from the center point, connect your subwoofer..

chchyong89 · 23rd April 2009, 04:31 PM

actually i not really understand.. ~.~

why no need to add another extra amp on it example a LM4651/52? ~.~
by the way, my bronze BR2 show it's weakness on movie, i need certain ooohmmm when playing movie..

guide me out please ..

AndrewT · 23rd April 2009, 04:38 PM

Hi,
use an inverting opamp as a summer amplifier.
Each channel is fed in through it's own resistor.
These meet at the opamp -IN input where the impedance is very low (virtual earth). Both signals add at this virtual earth and due to the very low impedance there is no crosstalk to the other channel.

If the opamp is configured as a CFB filter then the one opamp becomes the summer and low pass filter and sends it's combined signal on to the power amp.

If you are feeling very ambitious you can substitute the chipamp for the opamp and combine the whole shooting match into one chip.

ps,
DX has it all wrong.

pacificblue · 23rd April 2009, 06:06 PM

http://www.getelectron.com/subwoofer...amplifier.html
http://sound.westhost.com/project48.htm
http://www.linkwitzlab.com/Pluto/subwoofer.htm

Cal Weldon · 23rd April 2009, 08:46 PM

Simple.

Buy a plate amp for your woofer and use the speaker level inputs. The amp has a high pass for your satellites and the woofer XO is variable to match. Sound quality degradation is negligible. Done it many times.

Westerp · 23rd April 2009, 09:11 PM

http://english.cxem.net/amplifier/amplifier21.php

Schematic:

pcb:

layout:

chchyong89 · 24th April 2009, 03:28 AM

now this look interesting

Is it just simply connct parallel with my gainclone to the signal output source? By the way i will use one dualchannel opamp indeed of two mono channel op. But i still, don't get the meaning of R3, R5, and R7? why it need to be attenuater? For R3, is it tone control? and thanks, you have help me a lot

Dxvideo · 24th April 2009, 06:17 AM

Quote:

Originally posted by AndrewT
ps,
DX has it all wrong.

What is wrong?
Did you read my posting carefully?
Is this wrong do you think?

Westerp · 24th April 2009, 07:13 AM

Quote:

Originally posted by Dxvideo
Is this wrong do you think?

Not wrong as such but wrong in this application. You want to feed only the lows
to the sub amp and woofer.

23rd April 2009, 01:48 PM	#1
chchyong89 diyAudio Member Join Date: Apr 2009	How to spilt one channel out from stereo for woofer Hi, i am new to here, i have a quite stupid question to ask, suppose i have a gainclone stereo amplifier with two LM3886, how i can split out and modify to install another mono LM3886 to sound up a subwoofer speaker. An easy way to say is, to make it 2.0 to 2.1.. can you guys show me any schmatics for me thanks regards __________________ ~.~

23rd April 2009, 02:51 PM	#2
Dxvideo diyAudio Member Join Date: Nov 2003 Location: Turkey	Just add 10K resistors to each channels line level output, then connect their other pins together. And from this junction put another 10K to the gorund.. Means make a Y shape with 10K resistors.. One branch to left channel, one branch to right channel and one to ground.. Then from the center point, connect your subwoofer.. __________________ Best regards, Ozgur

23rd April 2009, 04:31 PM	#3
chchyong89 diyAudio Member Join Date: Apr 2009	actually i not really understand.. ~.~ why no need to add another extra amp on it example a LM4651/52? ~.~ by the way, my bronze BR2 show it's weakness on movie, i need certain ooohmmm when playing movie.. guide me out please .. __________________ ~.~

23rd April 2009, 04:38 PM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, use an inverting opamp as a summer amplifier. Each channel is fed in through it's own resistor. These meet at the opamp -IN input where the impedance is very low (virtual earth). Both signals add at this virtual earth and due to the very low impedance there is no crosstalk to the other channel. If the opamp is configured as a CFB filter then the one opamp becomes the summer and low pass filter and sends it's combined signal on to the power amp. If you are feeling very ambitious you can substitute the chipamp for the opamp and combine the whole shooting match into one chip. ps, DX has it all wrong. __________________ regards Andrew T.

23rd April 2009, 06:06 PM	#5
pacificblue diyAudio Member Join Date: May 2008	http://www.getelectron.com/subwoofer...amplifier.html http://sound.westhost.com/project48.htm http://www.linkwitzlab.com/Pluto/subwoofer.htm __________________ If you've always done it like that, then it's probably wrong. (Henry Ford)


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23rd April 2009, 08:46 PM	#6
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Simple. Buy a plate amp for your woofer and use the speaker level inputs. The amp has a high pass for your satellites and the woofer XO is variable to match. Sound quality degradation is negligible. Done it many times. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

23rd April 2009, 09:11 PM	#7
Westerp diyAudio Member Join Date: Jan 2006 Location: Amsterdam	http://english.cxem.net/amplifier/amplifier21.php Schematic: pcb: layout: __________________ http://tda1541a.com The Final List

24th April 2009, 03:28 AM	#8
chchyong89 diyAudio Member Join Date: Apr 2009	now this look interesting Is it just simply connct parallel with my gainclone to the signal output source? By the way i will use one dualchannel opamp indeed of two mono channel op. But i still, don't get the meaning of R3, R5, and R7? why it need to be attenuater? For R3, is it tone control? and thanks, you have help me a lot __________________ ~.~

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