2.1 LM3886 system layout

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krizas

Member
2016-03-14 9:53 pm
Dear All,

I am considering building LM3886 based chipamp for my 2.1 speaker system (2x40W 8ohm L/R + 75W 4ohm sub). Though I have never built an amp for a stereo system with subwoofer before. It is unclear for me how the general layout should look like.

I can think of two possible layouts:
  1. Crossover and 3 LM3886 modules in a single box, sharing one power supply unit.
  2. Crossover and 2 LM3886 modules in an amp box + separate LM3886 module with its own power supply unit built into/next to a subwoofer.

What are the advantages/disadvantages of one layout versus another?
 

tomchr

Member
Paid Member
2009-02-11 12:58 am
Calgary
www.neurochrome.com
If you run the LM3886 on ±28 V rails, you'll get 38-40 W into 8 Ω and 65-ish W into 4 Ω. The LM3886 is only guaranteed to be able to deliver 7 A peak, so 7*4 = 28 V peak is the highest output swing the LM3886 can sustain into a 4 Ω load.

I'd put everything into one box. Run the XO from a regulated supply that you branch off of the main supply. That's what I did in my 4xMOD86 + MiniDSP build this summer. It works fantastic. Pictures in this post: Modulus-86 Build Thread - Post #888.

The advantage of having everything in one enclosure is simplicity. One box. Cables go in. Cables go out. Done.
The disadvantage is the longer runs of speaker cable. Your 2.1 setup won't fix this. You need three mono blocks, one by each speaker/sub, to get the full advantage of separating the amps. The drawbacks of separate amps is that you run the most sensitive node in the system the farthest.

Tom
 

krizas

Member
2016-03-14 9:53 pm
Thanks Tom. I will go with single box solution. It appeared from the beginning that this option suited my needs better and was less complicated, however I could not find a short explanation of differences.

By the way, material on your website is incredibly helpful for tuning LM3886 design.
 
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