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Old 31st March 2005, 02:52 PM   #1
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Default My "audiophile" LM3886 approach

my modest contribution to this forum...

Mauro Penasa
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Old 31st March 2005, 03:20 PM   #2
Giaime is offline Giaime  Italy
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It looks good! But I'm not sure about the use of an opamp in front of the LM3886, many people there believe in a "less parts better" approach towards Gainclones. I don't know...

And what's that circuit (the first one on page 2)? Is it a speaker protection or a startup delay?

And where do you get LM3886 in Italy? How much you pay?
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Old 31st March 2005, 03:27 PM   #3
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Hi maupenas!

Very nice! Thorsten would like it..
But you have overtaken us! It's ages that my friend pushes me to realize this concept! Though he wants it a bit modified, so as to get "constant power" drive, instead of current drive.

For me, the question is: how this all react with Your speaker? [Mine is a two-way bass reflex]
Did you measure the actual Rout? Stability?

Ciao, George
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Old 31st March 2005, 03:40 PM   #4
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Hello,

I've just glanced at your design, so my question is surely silly. How does your speaker protection cope with negative DC offset?
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Old 31st March 2005, 03:55 PM   #5
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A very unusual design. The 3886 is just a power booster for the 318. I wonder how it sounds compared to the more traditional approach. Any problems with stability?
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Old 31st March 2005, 06:34 PM   #6
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No, it's not a power booster..

Doh, I was not looking close enough at the first glance - so I take it back - it IS a kind of a power booster.. though a tricky one. [it's not a unity gain buffer on the output..]

At first I was only looking at the 3886 circuit. My note was referring to that. I still would like to try one day.
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Old 31st March 2005, 06:49 PM   #7
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Ehm, what would you call it? It's got a unity gain and falls under the 318 feedback loop.
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Old 31st March 2005, 06:57 PM   #8
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sorry, analog_sa, as you see, in the meantime also I have recognized it

The opamp controls the output current..
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Old 31st March 2005, 07:05 PM   #9
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So as to be clear: the LM3886 is a voltage controlled bipolar current source in this configuration. It does not have any voltage gain; it has an input voltage/ output current transfer characteristic - which is, in this case, is 100.

And it is stable in this config.
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Old 31st March 2005, 07:07 PM   #10
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And it is stable in this config.
I am sure it is. What about the entire amp? I guess it's fine with the compensation caps.
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