My LM3886 chip amp

Denis.BR · 16th October 2007, 12:52 PM

I would like to share with you my new home made chip amp. Its based in a LM3886 chip.

I made the housing all in steel plate, very cheap and easy to find. The painting is in epoxy powder:

Everything assembled inside the housing. I assembled the amp circuit and power supply in a acrylic plate, witch is easier to drill and fix with bolts and nuts.

Two chips for stereo, one chip for subwoofer:

Power supply: an old transformer from a vintage receiver and two 10000uF 63v EPCOS capacitor hidden under the board.

Rear view. Heatsink visible for style an cooling.

Amp board:

Front view with stereo VU meter. The knob isn’t functional yet, but it is intended to control the subwoofer level. Instead using a regular LED for power on, I used a LED inside a optical relay box and connected to the front panel using a fiber optic. Very distinctive and bright.

I used the project shown in www.chipamp.com , and this power supply:http://www.chipamp.com/docs/lm3886-manual.pdf

It sounds very nice! I measured around 55w @ 8 ohms using 33V per rail

gni · 16th October 2007, 04:11 PM

Looks like it will work: parts look like you used up the parts box!
Great way to recycle old parts into a new functioning unit.

I've never seen the chips that far from the rest of the circuit.. . but if
it works. . .good going.

lgreen · 18th October 2007, 12:11 AM

ha! nice! Gotta love using up those old parts; your transformer is missing a few nuts I see.

Hey what's the blue dealie with the red and green LEDs on it?

Leolabs · 18th October 2007, 02:22 AM

Wow!Saw P2P but never seen this:multicore wires from PCB to chips!

Denis.BR · 18th October 2007, 02:32 AM

yep, it works indeed...

I chose this config because my PCB whas those "universal" (can't recall the proper name) and it was easyer to connect. The PCB had holes smaller than the LM's leads

gni · 18th October 2007, 03:12 PM

That means the feedback resistor is on the board and not soldered
directly to the chip. . .longer feedback loop? Or is it hidden by the
angle of the picture.

Denis.BR · 18th October 2007, 03:21 PM

yep, on the board.

But what's the difference? only a few inches away won't make any difference. After all, the energy is running at speed of light

davidallancole · 18th October 2007, 04:16 PM

Is that transformer from an old pioneer amp?

Denis.BR · 18th October 2007, 04:25 PM

no, from a Kenwood receiver

davidallancole · 18th October 2007, 04:32 PM

Cool. I have one just like that out of a pioneer, thats why I was wondering.

I see you have 3 chips there. What are you doing with the 3 in there?

16th October 2007, 12:52 PM	#1
Denis.BR diyAudio Member Join Date: Mar 2007	My LM3886 chip amp I would like to share with you my new home made chip amp. Its based in a LM3886 chip. I made the housing all in steel plate, very cheap and easy to find. The painting is in epoxy powder: Everything assembled inside the housing. I assembled the amp circuit and power supply in a acrylic plate, witch is easier to drill and fix with bolts and nuts. Two chips for stereo, one chip for subwoofer: Power supply: an old transformer from a vintage receiver and two 10000uF 63v EPCOS capacitor hidden under the board. Rear view. Heatsink visible for style an cooling. Amp board: Front view with stereo VU meter. The knob isn’t functional yet, but it is intended to control the subwoofer level. Instead using a regular LED for power on, I used a LED inside a optical relay box and connected to the front panel using a fiber optic. Very distinctive and bright. I used the project shown in www.chipamp.com , and this power supply:http://www.chipamp.com/docs/lm3886-manual.pdf It sounds very nice! I measured around 55w @ 8 ohms using 33V per rail

18th October 2007, 12:11 AM	#3
lgreen diyAudio Member Join Date: May 2003 Location: San Diego, USA	nice ha! nice! Gotta love using up those old parts; your transformer is missing a few nuts I see. Hey what's the blue dealie with the red and green LEDs on it? __________________ My DIY audio projects- PartTimeProjects.com.

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16th October 2007, 04:11 PM	#2
gni diyAudio Member Join Date: Sep 2006	Looks like it will work: parts look like you used up the parts box! Great way to recycle old parts into a new functioning unit. I've never seen the chips that far from the rest of the circuit.. . but if it works. . .good going.

18th October 2007, 02:22 AM	#4
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Wow!Saw P2P but never seen this:multicore wires from PCB to chips!

18th October 2007, 02:32 AM	#5
Denis.BR diyAudio Member Join Date: Mar 2007	yep, it works indeed... I chose this config because my PCB whas those "universal" (can't recall the proper name) and it was easyer to connect. The PCB had holes smaller than the LM's leads

18th October 2007, 03:12 PM	#6
gni diyAudio Member Join Date: Sep 2006	That means the feedback resistor is on the board and not soldered directly to the chip. . .longer feedback loop? Or is it hidden by the angle of the picture.

18th October 2007, 03:21 PM	#7
Denis.BR diyAudio Member Join Date: Mar 2007	yep, on the board. But what's the difference? only a few inches away won't make any difference. After all, the energy is running at speed of light

18th October 2007, 04:16 PM	#8
davidallancole diyAudio Member Join Date: Nov 2005	Is that transformer from an old pioneer amp?

18th October 2007, 04:25 PM	#9
Denis.BR diyAudio Member Join Date: Mar 2007	no, from a Kenwood receiver

18th October 2007, 04:32 PM	#10
davidallancole diyAudio Member Join Date: Nov 2005	Cool. I have one just like that out of a pioneer, thats why I was wondering. I see you have 3 chips there. What are you doing with the 3 in there?

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