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Old 6th February 2010, 06:47 PM   #11
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Thanks for the tips. I'll try it as is first and then if bass performance needs improving, I'll add some 4700uF-10,000uF caps on each c1/c2.

Even with that extra capacitance added, the snubber components are still optional as well, yes?
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Old 6th February 2010, 07:11 PM   #12
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Yes, snubbers are optional. Generally they supposed to improve definition of bass when large caps are being used. In a long run I found them too manipulative to a sound.

Some additional comments here:

my first try at a LM3886 layout, any comments/suggestions?

Blackgate caps out of production, so...
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Old 8th February 2010, 06:12 PM   #13
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Quote:
Originally Posted by taj View Post
Nice blue boards, Peter. Can I trade in my old gold ones for blue ones? [kidding!]

..Todd

The quality of these boards is quite good. And they look great too



Since I will be using both the stereo 4 channel amp and the 2 channel parallel amp with 4ohm speakers, I was planning on going a little different route with the cooling. Instead of using the supplied insulator film between chip and heatsink, I'm going to isolate the heatsinks from the chassis and attach the chips direct to the heatsink (with compound of course). I'm thinking this should provide at least slightly more effective cooling.

My plan is to use (2) rackmount cases, 3U size and put 2 pieces of aluminum heatsink in each one run parallel with each other. Each piece will cool one chip. Heatsink size for each chip is 10" x 3.5" x 2". Fins are 1.9" tall and .08" thick with a base thats 0.4" thick. I'm also considering picking up a small piece of copper bar between the chip and aluminum...might be overkill though.

The heatsink material can be seen here: It would be cut in half to provide the sizes needed. Heat Sink DIY HiFi Amplify Kit IGBT Cooling 10"x7"x2" - eBay (item 250577005422 end time Feb-14-10 21:05:14 PST)

The rackmount case can be seen here: http://cgi.ebay.com/3U-Audio-Rackmou...item5633f61111



One transformer per case, I dont think there will be any issues with fitting everything in there

Last edited by captainobvious; 8th February 2010 at 06:14 PM.
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Old 4th November 2010, 04:02 PM   #14
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Default LM4780 Parallel mode

Hi Peter,

From your LM4780 kit, what has to be changed to run it in Parallel mode?

Thanks
Do
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Old 5th November 2010, 01:21 AM   #15
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You will find all the info here: Kit arrived
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Old 5th November 2010, 01:36 AM   #16
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Default Bridge mode?

Yeah! me again...!

Do you also have instructions for bridge mode. Must be pretty similar to parallel mode.

Thanks
Do
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Old 5th November 2010, 10:41 PM   #17
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Bridged mode is the same as stereo version described here: AudioSector-chip amp kits, dacs, chassis

Use green option on schematic here: http://audiosector.com/lm4780%20amp.pdf

Please note that the amp won't convert unbalanced signal to balanced. You can use transformers for that purpose: Commercial Gainclone kit- building instructions
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Old 6th November 2010, 12:30 AM   #18
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Default Unbalanced to balanced

Hi Peter,

I was thinking about using a BurrBrown DRV134. What do you think about that?

Using a transfo, I would need a really good quality one in order to not alter the sound.

Do you have an example of what you would use as a very good quality transfo for this purpose at Mouser or Digikey or Parts Connexion...

This is an example I was able to find but don't know if it is a good choice or if I can find this in Canada. Don't know how to implement it either for both XLR and SE as input...
DIY BPA300 v2 6x LM3886 300W audio Amplifier

Thanks
Do
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