Need your opinion, how small gain can I use with LM3886 (how close to "flat amp")? - diyAudio
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Old 28th November 2008, 06:55 AM   #1
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Default 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!
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Old 28th November 2008, 07:11 AM   #2
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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.
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Old 28th November 2008, 07:46 AM   #3
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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.

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Old 28th November 2008, 07:55 AM   #4
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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.
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Old 28th November 2008, 08:22 AM   #5
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I'd like to see it at 2x, or 4x, or 8x--even multiples if you don't mind.
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Old 28th November 2008, 09:07 AM   #6
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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.
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File Type: gif lm3886_gain_3.gif (5.3 KB, 507 views)
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Old 29th November 2008, 04:55 AM   #7
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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)
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Old 29th November 2008, 06:29 AM   #8
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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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Old 29th November 2008, 06:36 AM   #9
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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 ?
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Old 29th November 2008, 06:55 AM   #10
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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?
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