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Old 16th June 2006, 09:27 PM   #1
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Default Dual3886

Long time reader, first time topicwriter!

This summer I have desided to do something about my spare lm3886.

objectivs
- two lm3886/board
- versatile module that can be configured in stereo, bridge and parallel mode
- on board power supply - just add transformer
- diy etched pcb

I use Eagle light which means that I'm limited to a board size of 100*80mm. Since I'm planning to etch my own pcb I want to make a single sided one. This makes it a little bit cramped on the pcb!

I would very much like you to take a look at my board before I start to etch and buy components.
Should I give it a try? Is there any obvious errors? The "groundplane" seems a bit anorectic to me...

Schematic
Board

/Per
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Old 19th June 2006, 01:56 PM   #2
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Why don't you try using inverting amps for both stages?

That may eliminate your DC servo and some other parts too. Things will be less cramped too.

Completely agreed on doing a single-side pcb.
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Old 19th June 2006, 04:45 PM   #3
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One quick glance..the servo IC o/p should be fed to inv i/p of 3886 ? right ? or interchange the servo ic i/p pins either way same result...
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Old 19th June 2006, 09:17 PM   #4
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Quote:
One quick glance..the servo IC o/p should be fed to inv i/p of 3886 ? right ? or interchange the servo ic i/p pins either way same result...
That's true! I knew it was a good idea letting someone else check my work. Thanks a lot!

Quote:
Why don't you try using inverting amps for both stages?

That may eliminate your DC servo and some other parts too. Things will be less cramped too.
Let's see if I understand you.
If I decide to keep the dc-servos, I belive the number of components is almost the same in inverting and non-inverting mode. To eliminate components I have to get rid of the dc-servos, right? Is an inverting lm3886 a better choice without dc-servos?
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Old 19th June 2006, 11:35 PM   #5
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Quote:
[i]
Let's see if I understand you.
If I decide to keep the dc-servos, I believe the number of components is almost the same in inverting and non-inverting mode. To eliminate components I have to get rid of the dc-servos, right? Is an inverting lm3886 a better choice without dc-servos? [/B]
To start with I think servos have to be different for nulling DC in inverting amps.

But that is not my point. The main purpose of DC servos is to cut DC offset. On non-inverting amps you use a large capacitor on the feedback. On inverting amps you can get away with smaller cap, usually series 4.7uF or less, that can be a film type.

Parts count is also less, but not that much really, perhaps one resistor and one capacitor less. It is if you don't add the servo.

IMHO a well implemented inverting gainclone will sound a bit better than a non-inverting one, but that may not be as important if you use things like good de-coupling and short pcb paths. Using less parts may make such paths really short.

That's all I intended to say.
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Old 27th August 2006, 05:16 PM   #6
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Default New design

It's been a while... DC-servos is gone and finally I have settled with a design based on Upupa Epops Pa03. PCB is etched (105um copper took 1hr to etch ) and drilled...

Click the image to open in full size.

...and all components is mounted. No pictures of that yet.
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Old 30th August 2006, 09:55 AM   #7
1000W is offline 1000W  India
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Can you please attach the files again, they dont show up on your previous post
rgds,
/mp
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Old 30th August 2006, 05:59 PM   #8
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Ok. I'll give it one more try.

#1
#2
#3
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Old 31st August 2006, 07:41 PM   #9
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Thats sweet !

Where'd you get those inductors? 0.7µH, right? I have the craving for 0.7µH axial through hole air core inductors right now!
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Old 1st September 2006, 01:22 AM   #10
maxw is offline maxw  United Kingdom
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Good job!
Sound good?
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