Lm3886 Bpa - Page 8

jaudio · 28th May 2005, 09:31 PM

Are all the resistors 1% or .1%?. I didnt bother with the .1ohm output resistors. I used .22ohm.

The only time I got 150mv is when I didnt ground the input properly.

You should email Jackinnj. He has more experience with the lm4780 chip?

thomasfw · 2nd June 2005, 07:40 AM

Dear All,

Please see the attachment !

Can I reduce the cost by don't put the "Input Cap" for each LM3886 ?

Thanks !

Thomas

Upupa Epops · 2nd June 2005, 08:14 AM

Don't make it with DRV 134 - it's not quite good sounding circuit

.

jaudio · 2nd June 2005, 10:29 AM

The lm3886 needs a gain of aleast 10. If you want to use a gain of four use the OPA chips (549 or 541). The OPA chips cost 3 times as much as lm3886. You can leave out the input caps,but you might have a problem with dc offset.

macboy · 2nd June 2005, 01:28 PM

Quote:

The lm3886 needs a gain of aleast 10.

Nice catch. It's no wonder that the amp is oscillating. Do people even bother to read datasheets anymore?

troystg · 2nd June 2005, 04:11 PM

Quote:

Originally posted by Upupa Epops
Don't make it with DRV 134 - it's not quite good sounding circuit .

Pavel-

So what do you suggest as a replacement?

mateo88 · 4th June 2005, 02:06 AM

Is it even neccessary to use the DRV134 or a similar chip at the input?

i.e., can you just take two of image 5.2.1 in the AN-1192 datasheet and parallel them?

jaudio · 4th June 2005, 06:10 AM

Quote:

Originally posted by mateo88

i.e., can you just take two of image 5.2.1 in the AN-1192 datasheet and parallel them?

Two bridged amp in parallel would still require output resistors. Image 7.2.4 would be better.

mateo88 · 4th June 2005, 01:00 PM

Yes, I know it would still require output resistors. I guess my real question is in figure 7.2.4, why is U5 needed?

jaudio · 4th June 2005, 03:22 PM

U1 is used to isolate the source from the chips low impedance input. The input without the buffer, would be less than or around 500ohms. Input impedance plays a role in frequecy response.

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28th May 2005, 09:31 PM	#71
jaudio diyAudio Member Join Date: Oct 2004	Are all the resistors 1% or .1%?. I didnt bother with the .1ohm output resistors. I used .22ohm. The only time I got 150mv is when I didnt ground the input properly. You should email Jackinnj. He has more experience with the lm4780 chip?

2nd June 2005, 08:14 AM	#73
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Don't make it with DRV 134 - it's not quite good sounding circuit .

2nd June 2005, 10:29 AM	#74
jaudio diyAudio Member Join Date: Oct 2004	The lm3886 needs a gain of aleast 10. If you want to use a gain of four use the OPA chips (549 or 541). The OPA chips cost 3 times as much as lm3886. You can leave out the input caps,but you might have a problem with dc offset.

4th June 2005, 02:06 AM	#77
mateo88 diyAudio Member Join Date: May 2004 Location: Argyle, Texas	Is it even neccessary to use the DRV134 or a similar chip at the input? i.e., can you just take two of image 5.2.1 in the AN-1192 datasheet and parallel them?

4th June 2005, 01:00 PM	#79
mateo88 diyAudio Member Join Date: May 2004 Location: Argyle, Texas	Yes, I know it would still require output resistors. I guess my real question is in figure 7.2.4, why is U5 needed?

4th June 2005, 03:22 PM	#80
jaudio diyAudio Member Join Date: Oct 2004	U1 is used to isolate the source from the chips low impedance input. The input without the buffer, would be less than or around 500ohms. Input impedance plays a role in frequecy response.

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