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Old 16th August 2012, 07:30 PM   #2191
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Hi, this is my amplifier with LM3886. Schematic based on Bob Cordel's Super Gainclone. Enclosure of fabrique BMW 7 series car amplifier by Philips.
Some pictures:

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Old 19th August 2012, 05:29 PM   #2192
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Cool I'm calling this the ParalleLM3886

Introducing my latest creation . . . a 4-channel amplifier made from 4 pairs of parallel LM3886 chips. This project started when I had the opportunity to get a good deal on 12 LM3886ís, 2 huge torroidal transformers, and a bunch of boards and caps through the diyAUDIO Swap Meet forum. I plan to use it with an active X-over for a pair of speakers & subwoofers in my office/ audio hobby room.
Some features of this amplifier:
It follows National Semiconductorís application note AN-1192 (http://www.ti.com/lit/an/snaa021a/snaa021a.pdf) for the PA100 exactly, using boards from ChipAmp.com. Itís really easy to use the ChipAmp.com boards for this circuit. The boards have all the connections necessary except for the input filter, which I soldered directly to the RCA inputs, and the 0.1 ohm output resistors, which are soldered directly to the boardsí ďOUTĒ holes. To parallel the chips, one only needs to build each board, then Ė all the wires going to or coming from each board Ė make into a ďYĒ to put the boards in parallel. Itís that simple!
A separate power supply for each channel. Power supplies are ChimAmp.com ďsnubberizedĒ design, so thatís 32 MUR860s for those of you counting. Specified filter caps for Brianís PS are a pair of 10,000ĶF, but I got a good deal on a bunch of 6,800ĶF caps, so I used 4 of those per PS. The extra pairs are soldered to the boardís output holes.
Each channel has a 2-pole, 2-throw switch on the front panel. The UP position both completes the circuit to the PS LEDs (also located on the front of the chassis) and completes the circuit from the LM3886ís pins 8 to pins 4, which turns off the mute feature.
The amplifier is supposed to have an Elliott Sounds Products P37 softstart, but I couldnít get it to work. Iíve built one successfully before. I compared it to my working P37 and I canít find any difference. So Iím stumped with this one! There must be a bad component. Iíve got other projects to move on to, but I WILL get back to this softstart eventually!
I really want to take measurements. I have an oscilloscope, but Iíve not been able to find any free signal generator software that works with my 64-bit computer. A lot of software made for the 32-bit machines wonít work on 64-bit machines. If anyone can help me out here, Iíd really appreciate it! I was able to measure +/- 32V rails, and -200mV offset.
How does it sound? Iíve been playing DVDs, CDís and windows lossless files through my computer, using the USB out to a Twisted Pear USB D/A converter with a GoldPoint attenuator, running a pair of Vandersteen 3Aís. Iím accustomed to listening to my DX Blame MKIII build, and a chipamp really canít compare to a 200W class A/B amp. Itís a little weak in the bass, which may be because the Vandersteensí impedance drops to 3 ohms between 30Hz-40Hz, which is pushing the limits of this design. The heatsinks get pretty hot. It doesnít quite have the clarity and snap of the DX Blame either. I think it will be more than adequate for casual listening on pair of bookshelf speakers and a little subwoofer.
Attached Images
File Type: jpg testing power supply.JPG (402.9 KB, 494 views)
File Type: jpg front view.JPG (290.1 KB, 508 views)
File Type: jpg back view.JPG (351.7 KB, 533 views)
File Type: jpg PS ready to install 2.JPG (256.2 KB, 569 views)
File Type: jpg top view.JPG (482.8 KB, 567 views)
File Type: jpg softstart.JPG (170.0 KB, 563 views)
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Old 20th August 2012, 09:05 AM   #2193
AndrewT is offline AndrewT  Scotland
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Byron,
this is a pic Thread.
Please move your technical description to another section.
You can link both to each other.
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Old 21st August 2012, 08:15 AM   #2194
Variac is offline Variac  United States
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Oh, I think a bit of description is appropriate. Otherwise people will have lots of questions..

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Originally Posted by AndrewT View Post
Byron,
this is a pic Thread.
Please move your technical description to another section.
You can link both to each other.
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Old 21st August 2012, 04:29 PM   #2195
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Default Amazing!!!

Quote:
Originally Posted by morpheous87 View Post
Hi, this is my amplifier with LM3886. Schematic based on Bob Cordel's Super Gainclone. Enclosure of fabrique BMW 7 series car amplifier by Philips.
...snipped...
Your Philips enclosure/heatsink is amazing! Nice!!!
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Old 7th September 2012, 08:43 AM   #2196
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Extraordinary creativity!
This most compact and neat layout I have come across.
Are you willing to share the parallel amp layout?
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Old 10th September 2012, 05:21 PM   #2197
sasmit is offline sasmit  India
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Default my paralell lm4780

Finally found some time to put together the amp. The basic amp components have been ready for long but putting everything together is what took a lot of time. I went through 2 versions of the amplifier boards before I was happy. The preamp went through 1 revision. There's still some work that needs to be done, but I could put the the amp together without them. A a dc protector cum click/pop suppressor controlled through the micro controller in the preamp is still being worked on.
The power supply board was made after going through nationals audio amp power supply design guide, I have made some changes though. National's design had a bridge rectifier unit however I changed to a discrete diodes, I also added fuses on the power supply board itself.There are 4*10000uF caps on board.
The power transformer is a 0-20,0-20 200VA unit , this gives me +- 28V rails, each amp board contains a 4780 in parallel configuration. The amp runs fairly cool even in ambient temperatures of around 29~30C.

Some pics of the amp board :
Attached Images
File Type: jpg 2012-05-06 16.09.31.jpg (374.4 KB, 440 views)
File Type: jpg 2012-05-06 16.09.54.jpg (323.0 KB, 351 views)
File Type: jpg 2012-05-06 16.10.46.jpg (280.5 KB, 233 views)
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Old 10th September 2012, 05:41 PM   #2198
sasmit is offline sasmit  India
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Default my paralell lm4780

It took a long time for me to decide the chassis , I had initially thought of making this the traditional way using aluminum sections and using a machined front panel. I was going through the pages of stereophile and found some very neat looking wood chassis and found some very classy looking wood chassis on the solid state gallery also, then I dropped the aluminum idea and got working on the wooden chassis. Wood is much easier to work with, besides you get professional help i.e. a carpenter quite easily. I got all the pieces cut and machined at a carpenters workshop near my home. The heatsinks were drilled and then tapped using a M4 tap drill, some aluminum angles hold everything together using M4 screws to attach them to the heatsink and self threading wood screws to attach them to the wooden pieces. The holes and cutouts were all done at the carpenters workshop. I designed the frontpanel with a big slot where I could basically press fit a preamplifier module. The preamplifier module is fitted on to a translucent plexiglass sheet. The sheet is completely dark except when the LCD backlgiht in the preamp board is on.

I first trial fit the module onto a tranperent plexiglass sheet to check the fit and hole positioning, using this sheet as a template then drilled onto the translucent plexiglass sheet.I still need to polish the wood and glue a push button onto the front panel. Below are some pics of the front panel and the chassis.
Attached Images
File Type: jpg 2012-07-25 22.47.28.jpg (186.7 KB, 410 views)
File Type: jpg IMG_5910.JPG (144.5 KB, 518 views)
File Type: jpg 2012-06-01 09.17.05.jpg (365.7 KB, 534 views)
File Type: jpg IMG_5929.JPG (353.0 KB, 486 views)
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Old 10th September 2012, 05:49 PM   #2199
sasmit is offline sasmit  India
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Default my paralell lm4780

Another shot of the chassis.
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File Type: jpg IMG_5914.JPG (370.1 KB, 523 views)
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Old 10th September 2012, 07:12 PM   #2200
udailey is offline udailey  United States
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Nice job Sasmit! I like it.
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