LM3886 GC - "Simplest Ever Amplifier Bridging"

jweber · 12th January 2005, 10:58 AM

Has anyone tried the simple bridging method described by
Rod Elliot?
http://sound.westhost.com/project20.htm

Nice when it works, but I have only two LM3886 chips left and don't
like to blow them up...

Any disadvantages doing it this way?

Thanks for your comments.

Upupa Epops · 12th January 2005, 11:26 AM

You can use it, but instead TL 072 give OPA 2134 and instead both 100 k resistors give there 10 k.

jweber · 12th January 2005, 12:18 PM

Have a look at the drawing again - it is NOT a bridging adapter!

It seems you can bridge two LM3886 chips directly with two additional resistors.

pinkmouse · 12th January 2005, 12:21 PM

Quote:

Originally posted by jweber
Has anyone tried the simple bridging method described by
Rod Elliot?
http://sound.westhost.com/project20.htm

Why don't you just use the circuit shown in the LM4780/1 datasheet, you can't get much simpler.

Upupa Epops · 12th January 2005, 12:36 PM

This solution is worse, have higher distortion.

BeanAnimal · 12th January 2005, 08:03 PM

which solution is worse?

1) Rod Elliots
2) Rod Eliots with OPA substitute
3) The 4780 datasheet solution

The last post was ambiguous to say the least.

theChris · 12th January 2005, 08:11 PM

i'd have to assume #1. it looks like distortion from amp 1 would then get distorted by amp 2, then add to the output.

leadbelly · 12th January 2005, 08:23 PM

Rod Elliot's article is being quoted out of context...he is addressing the simplest way to bridge a couple of commercial amps.

For scratch built DIY you would be better off just building one of the different designs discussed on this forum most often.

tschrama · 12th January 2005, 08:42 PM

I dunno if Rod Elliots simplest bridging adaptor is worse....

The distortion products of the non-inverting amplifier are being fed to the inverting amplifier: so those non-inverting-amplifier-distorion-products will cancell out. The only distortion you are left with are the distortion products of the inverting amp (and the diustortion of the distortion products, far to low to be significant I assume).

So.. You are left with a bridged amplifier having the same distortion specs as a non-bridged amp in halve the load..

versus...

When a perfect balanced signal is obtianed from a unballanced signal and this is fed to two equal amplifiers, distrotion of each amplifier alone is like driveing halve the load but..

the even-harmonics tend to subtract from each amplifier, while the uneven-harmonics tend to sum from each amplifier... this might even be worse...

go with Elliot, that guy never failed me once....

TwoSpoons · 13th January 2005, 02:37 AM

Quote:

Originally posted by tschrama

The distortion products of the non-inverting amplifier are being fed to the inverting amplifier: so those non-inverting-amplifier-distorion-products will cancell out.

Nonsense. The distortion (and noise) from the first amp will be distorted by the second amp. You will also get intermod products on the distortion. Its a non-linear process, not just add/subtract.

12th January 2005, 08:11 PM	#7
theChris diyAudio Member Join Date: Dec 2001 Location: SIUE, Illinois, USA	i'd have to assume #1. it looks like distortion from amp 1 would then get distorted by amp 2, then add to the output. __________________ if only it could be used for good, not evil...

12th January 2005, 08:23 PM	#8
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Rod Elliot's article is being quoted out of context...he is addressing the simplest way to bridge a couple of commercial amps. For scratch built DIY you would be better off just building one of the different designs discussed on this forum most often. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

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12th January 2005, 10:58 AM	#1
jweber diyAudio Member Join Date: Jun 2004 Location: Buende	LM3886 GC - "Simplest Ever Amplifier Bridging" Has anyone tried the simple bridging method described by Rod Elliot? http://sound.westhost.com/project20.htm Nice when it works, but I have only two LM3886 chips left and don't like to blow them up... Any disadvantages doing it this way? Thanks for your comments.

12th January 2005, 11:26 AM	#2
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	You can use it, but instead TL 072 give OPA 2134 and instead both 100 k resistors give there 10 k.

12th January 2005, 12:18 PM	#3
jweber diyAudio Member Join Date: Jun 2004 Location: Buende	Have a look at the drawing again - it is NOT a bridging adapter! It seems you can bridge two LM3886 chips directly with two additional resistors.

12th January 2005, 12:36 PM	#5
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	This solution is worse, have higher distortion.

12th January 2005, 08:03 PM	#6
BeanAnimal diyAudio Member Join Date: Jan 2005 Location: Pittsburgh	which solution is worse? 1) Rod Elliots 2) Rod Eliots with OPA substitute 3) The 4780 datasheet solution The last post was ambiguous to say the least.

12th January 2005, 08:42 PM	#9
tschrama diyAudio Member Join Date: Jul 2001 Location: The Netherlands	I dunno if Rod Elliots simplest bridging adaptor is worse.... The distortion products of the non-inverting amplifier are being fed to the inverting amplifier: so those non-inverting-amplifier-distorion-products will cancell out. The only distortion you are left with are the distortion products of the inverting amp (and the diustortion of the distortion products, far to low to be significant I assume). So.. You are left with a bridged amplifier having the same distortion specs as a non-bridged amp in halve the load.. versus... When a perfect balanced signal is obtianed from a unballanced signal and this is fed to two equal amplifiers, distrotion of each amplifier alone is like driveing halve the load but.. the even-harmonics tend to subtract from each amplifier, while the uneven-harmonics tend to sum from each amplifier... this might even be worse... go with Elliot, that guy never failed me once....