bridging an LM4881 headphohne amplifier? Can it be done?

soundNERD · 31st March 2004, 02:23 AM

Hi, I have a some LM4881 chips and have built a headphone amplifier for my portable CD player. The sound is excellent, so I would like to bridge them. The problem, though, is that they only have one input. Is there any way to bridge them short of using something like a DRV134 to invert one amp's input?

thanks!
mike

Alexander Rice · 31st March 2004, 11:20 AM

just stick an inverting buffer before one of the amplifiers

soundNERD · 31st March 2004, 12:39 PM

like the DRV134 right? that takes one signal, invertes it, balences the inverted and non-inverted inputs then has two outputs of the same signal, inverted and non-inverted.

The only problem with that is I only have one and would need two for stereo. I don't think with headphones you would notice the difference when one amp is inverted and not the other, so I could just stick an inverting opamp before the input of one of the amps, right?

Alexander Rice · 31st March 2004, 12:54 PM

that is what i said

- inverting buffer = inverting op amp with unity gain, any old thing'll do as long as it i unity gain stable since even TL072 will have a bandwidth well into RF, i reccomend the NE5532 for this type of thing for it's low noise and good value

soundNERD · 31st March 2004, 12:56 PM

OK!
Thanks!

-mike

paulb · 31st March 2004, 01:33 PM

Do you plan to modify your headphone cable to separate the common connection to each channel? Bridging won't work with a 3-wire cable; you need all 4 wires.

soundNERD · 1st April 2004, 01:28 AM

yes, my cable is from a standard pair of headphones, so the connector splits into two seperate cables, one with L and gnd, and the other with R and gnd.

thanks for pointing that out though.

-mike

31st March 2004, 02:23 AM	#1
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	bridging an LM4881 headphohne amplifier? Can it be done? Hi, I have a some LM4881 chips and have built a headphone amplifier for my portable CD player. The sound is excellent, so I would like to bridge them. The problem, though, is that they only have one input. Is there any way to bridge them short of using something like a DRV134 to invert one amp's input? thanks! mike

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31st March 2004, 11:20 AM	#2
Alexander Rice diyAudio Member Join Date: Jul 2003 Location: Cambridge	just stick an inverting buffer before one of the amplifiers

31st March 2004, 12:39 PM	#3
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	like the DRV134 right? that takes one signal, invertes it, balences the inverted and non-inverted inputs then has two outputs of the same signal, inverted and non-inverted. The only problem with that is I only have one and would need two for stereo. I don't think with headphones you would notice the difference when one amp is inverted and not the other, so I could just stick an inverting opamp before the input of one of the amps, right?

31st March 2004, 12:54 PM	#4
Alexander Rice diyAudio Member Join Date: Jul 2003 Location: Cambridge	that is what i said - inverting buffer = inverting op amp with unity gain, any old thing'll do as long as it i unity gain stable since even TL072 will have a bandwidth well into RF, i reccomend the NE5532 for this type of thing for it's low noise and good value

31st March 2004, 12:56 PM	#5
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	OK! Thanks! -mike

31st March 2004, 01:33 PM	#6
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	Do you plan to modify your headphone cable to separate the common connection to each channel? Bridging won't work with a 3-wire cable; you need all 4 wires.

1st April 2004, 01:28 AM	#7
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	yes, my cable is from a standard pair of headphones, so the connector splits into two seperate cables, one with L and gnd, and the other with R and gnd. thanks for pointing that out though. -mike

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