Need your opinion, how small gain can I use with LM3886 (how close to "flat amp")?

danielwritesbac · 28th November 2008, 07:55 AM

I need a good opinion on how little (small) gain I can use with lm3886 and still be able to use its full power?

I'd like to do an experiment that involves much more input, much less gain. If I use the minimum gain of 10, would I be overdriving the input before the LM3886 is producing its 68 watts? If so, how much gain do I need in order to stay out of trouble?

Thanks!

theAnonymous1 · 28th November 2008, 08:11 AM

It says right in the datasheet the IC needs at least a gain of 10 to be stable. I don't think you will be overdriving the input at full power; it can take a 60V differential input signal when used with an 80V supply.

Nickolay Shvydky · 28th November 2008, 08:46 AM

With appropriate feedback circuit, you can make it work even with gain = 1 (in inverted mode). I can give you exact schematic if you'll tell me what gain you need.

Nick

Will · 28th November 2008, 08:55 AM

Quote:

Originally posted by Mykola
With appropriate feedback circuit, you can make it work even with gain = 1 (in inverted mode). I can give you exact schematic if you tell me what gain you need.

Hi there, do publish the feedback circuit for a gain=1 amplifier. That's interesting. Many thanks.

danielwritesbac · 28th November 2008, 09:22 AM

I'd like to see it at 2x, or 4x, or 8x--even multiples if you don't mind.

Nickolay Shvydky · 28th November 2008, 10:07 AM

This one for example has a gain = 3.
--------------------------------------------------
Sorry, I was simulating and did not notice your new posts. I'll post tommorow what you need.

danielwritesbac · 29th November 2008, 05:55 AM

Its a good illustration.

My question was really about a non-inverting LM3886.
How little gain can I use there and still have all of its power available, but without overdriving the LM3886 input?

In a related question, can 100R or 1k be used for input load and and NFB? (pre=headphone amp)

Nickolay Shvydky · 29th November 2008, 07:29 AM

Common Mode Input Voltage ( V+ or V- )and | V+ | + | V- | <= 80V. So I think it could work for a noninverting LM3886 too, but distortion will be much higher than in inverting.

Nickolay Shvydky · 29th November 2008, 07:36 AM

Quote:

Originally posted by danielwritesbac

In a related question, can 100R or 1k be used for input load and and NFB? (pre=headphone amp)

You mean R3 and R14 ?

danielwritesbac · 29th November 2008, 07:55 AM

Quote:

Originally posted by Mykola
Common Mode Input Voltage ( V+ or V- )and | V+ | + | V- | <= 80V. So I think it could work for a noninverting LM3886 too, but distortion will be much higher than in inverting.

Inverting is fine then. I take it that we can invert both the amp and the pre so that it will come out straight?

28th November 2008, 07:55 AM	#1
danielwritesbac diyAudio Member Join Date: Nov 2007	Need your opinion, how small gain can I use with LM3886 (how close to "flat amp")? I need a good opinion on how little (small) gain I can use with lm3886 and still be able to use its full power? I'd like to do an experiment that involves much more input, much less gain. If I use the minimum gain of 10, would I be overdriving the input before the LM3886 is producing its 68 watts? If so, how much gain do I need in order to stay out of trouble? Thanks!

28th November 2008, 08:11 AM	#2
theAnonymous1 diyAudio Member Join Date: Feb 2004 Location: Anonymityville	It says right in the datasheet the IC needs at least a gain of 10 to be stable. I don't think you will be overdriving the input at full power; it can take a 60V differential input signal when used with an 80V supply. __________________ "If you don't like funerals don't kick sand in ninja's face."

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28th November 2008, 08:46 AM	#3
Nickolay Shvydky diyAudio Member Join Date: Apr 2005 Location: Rochester, NY	With appropriate feedback circuit, you can make it work even with gain = 1 (in inverted mode). I can give you exact schematic if you'll tell me what gain you need. Nick

28th November 2008, 09:22 AM	#5
danielwritesbac diyAudio Member Join Date: Nov 2007	I'd like to see it at 2x, or 4x, or 8x--even multiples if you don't mind.

29th November 2008, 05:55 AM	#7
danielwritesbac diyAudio Member Join Date: Nov 2007	Its a good illustration. My question was really about a non-inverting LM3886. How little gain can I use there and still have all of its power available, but without overdriving the LM3886 input? In a related question, can 100R or 1k be used for input load and and NFB? (pre=headphone amp)

29th November 2008, 07:29 AM	#8
Nickolay Shvydky diyAudio Member Join Date: Apr 2005 Location: Rochester, NY	Common Mode Input Voltage ( V+ or V- )and \| V+ \| + \| V- \| <= 80V. So I think it could work for a noninverting LM3886 too, but distortion will be much higher than in inverting.

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