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Old 4th August 2002, 06:33 AM   #1
Jean is offline Jean  United States
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Default lm 3876 impressions

Just for fun today I put together very simple amplifier based on the lm 3876 circuit. I used Avel 25-0-25 transformer, 25a bridge, and two 10,000 uF Mallory for the power supply. I didn't really know what to expect when it was complete. I am using onkyo 2ch receiver connected to my computer and diy 2way speakers. I went ahead and replaced one channel with the lm3876 ic amplifier and fired it up. I was surprised that it sounded better than my receiver. The biggest difference in sound is the bass response, compared to the receiver it made my right speaker sound much better. There is no hum or noise when there is no signal, don't hear anything with my ear close the speaker. I used my maudio 24/96 as the source w/o a passive volume control in line.

I am going to finish it up and use it as a computer speaker amplifier

I am really impressed with this little IC.

thanks for reading.
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Old 4th August 2002, 10:02 AM   #2
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Default Re: lm 3876 impressions

What circuit did you use? Pictures?

dave
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Old 4th August 2002, 07:36 PM   #3
Jean is offline Jean  United States
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Dave,

I used this circuit -
Click the image to open in full size.

Don't have pictures yet, I am working out some details on the chassis. I just soldered everything ptp.
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Old 5th August 2002, 05:20 AM   #4
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Default ptp

Here it is

Click the image to open in full size.
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Old 5th August 2002, 05:44 AM   #5
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Nice dead bug you have there... one of the things that pushes the peformance of these up is how physically short you can get the feedback resistor. Some guys will actually shave back some of the plastic and mount an SMD resistor to get a very short path -- yours is longish.

dave
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Old 5th August 2002, 01:32 PM   #6
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I do not have any experience with these except for servicing consumer gear using them.
In the typical Jap home amp they work quite decently imo.

In my experience on other amps I have found that the quality of the feedback AC shunt (R5 in above diagram) is important. Decoupling caps are important too ime.
Ime, SMPS grade caps work a lttle better and can give a more pleasant sound.

Dave, any experience with this on these type amps ?

Eric.

Ps - I have recovered an SMD chip in the past by grinding the epoxy back with a dremel tip and exposing the broken leg so that I could attach a wire. Not difficult at all.
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Old 5th August 2002, 02:10 PM   #7
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Hi Eric,
What is a dremel tip?
Vivek
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Old 5th August 2002, 02:54 PM   #8
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Default Dentists Drill

Like this Dremel tip - Flat non cutting end and cylindrical cutting sides.

Eric.
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Old 5th August 2002, 04:09 PM   #9
Vivek is offline Vivek  India
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OK. Thanks.
Vivek
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Old 5th August 2002, 05:51 PM   #10
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Quote:
Originally posted by mrfeedback
Dave, any experience with this on these type amps ?
Still in the parts gathering stage. Got chips, trafos, PS caps, heatsinks... mostly just need that rarest of parts -- time.

dave
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