How easy is it to bridge vs parallel?

Ulew · 31st January 2009, 04:23 PM

Hi!

When you want to parallel two LM3886, you just use two similar amps and one 1kohm resistors on the input on each amp? That's how I've understood it when reading different posts and the AN-1129. Is that correct?

To bridge two amps is a bit trickier, isn't it? It's not just to switch the inputs on one amp, right? Which is the easiest way to bridge?

(I've got plans to build an amp that can be switched between bridge and parallel, depending on the impedance of the speaker. Is that a good idea?)

Puffin · 31st January 2009, 05:41 PM

Read the NS data sheet. That's what I did to make a bridged LM3886.

Ulew · 31st January 2009, 05:54 PM

Well, what NS datasheet? AN-1129? I've read it and it seems that it's not possible to make an amp that can be switched between bridge/parallel, because you have to change some components from the original schematics. Correct?

woody · 31st January 2009, 06:08 PM

When you parallel the amps each amp needs an output resistor. This is to take care of any difference in the dc offset between amps I believe a small value like .1ohm will probably do.

Ulew · 31st January 2009, 06:22 PM

Ok, thank you! I saw it now in AN-1129. 0.1 ohm 3W, it says!

paulb · 31st January 2009, 06:31 PM

Quote:

Originally posted by Ulew
(I've got plans to build an amp that can be switched between bridge and parallel, depending on the impedance of the speaker. Is that a good idea?)

Your power supply could be quite different for different speaker impedances. Chip amps are cheap. Why not just build two amps?

Ulew · 31st January 2009, 06:33 PM

Quote:

Originally posted by paulb

Your power supply could be quite different for different speaker impedances. Chip amps are cheap. Why not just build two amps?

Oh, that's a bit problematic! I'll skip that plan. I just thought it would be a fun thing to build!

Redshift187 · 31st January 2009, 08:15 PM

To me, parallel is more difficult because the resistor tolerances must be better (0.1%) so that the output is close to the same so the chips don't "fight" each other.

I think the easiest idea for a switchable 8 ohm to 4 ohm setup would be a switch to change the power supply voltage.

wakibaki · 31st January 2009, 08:25 PM

Treat it as a 4 ohm design for dissipation purposes and plug in any speaker you want.

w

Ulew · 31st January 2009, 08:29 PM

But what I want is to get full power into 4 or 8 ohm-speakers. If I go for a parallel amp and use 8 ohm-speakers I won't get as much power as from a bridged one, right?

31st January 2009, 04:23 PM	#1
Ulew diyAudio Member Join Date: Oct 2008	How easy is it to bridge vs parallel? Hi! When you want to parallel two LM3886, you just use two similar amps and one 1kohm resistors on the input on each amp? That's how I've understood it when reading different posts and the AN-1129. Is that correct? To bridge two amps is a bit trickier, isn't it? It's not just to switch the inputs on one amp, right? Which is the easiest way to bridge? (I've got plans to build an amp that can be switched between bridge and parallel, depending on the impedance of the speaker. Is that a good idea?)

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31st January 2009, 05:41 PM	#2
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Read the NS data sheet. That's what I did to make a bridged LM3886.

31st January 2009, 05:54 PM	#3
Ulew diyAudio Member Join Date: Oct 2008	Well, what NS datasheet? AN-1129? I've read it and it seems that it's not possible to make an amp that can be switched between bridge/parallel, because you have to change some components from the original schematics. Correct?

31st January 2009, 06:08 PM	#4
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	When you parallel the amps each amp needs an output resistor. This is to take care of any difference in the dc offset between amps I believe a small value like .1ohm will probably do.

31st January 2009, 06:22 PM	#5
Ulew diyAudio Member Join Date: Oct 2008	Ok, thank you! I saw it now in AN-1129. 0.1 ohm 3W, it says!

31st January 2009, 08:15 PM	#8
Redshift187 diyAudio Member Join Date: Aug 2008	To me, parallel is more difficult because the resistor tolerances must be better (0.1%) so that the output is close to the same so the chips don't "fight" each other. I think the easiest idea for a switchable 8 ohm to 4 ohm setup would be a switch to change the power supply voltage.

31st January 2009, 08:25 PM	#9
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	Treat it as a 4 ohm design for dissipation purposes and plug in any speaker you want. w

31st January 2009, 08:29 PM	#10
Ulew diyAudio Member Join Date: Oct 2008	But what I want is to get full power into 4 or 8 ohm-speakers. If I go for a parallel amp and use 8 ohm-speakers I won't get as much power as from a bridged one, right?

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