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Old 31st December 2002, 12:04 PM   #1
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Default Lm3886 Pcb

I am a stingy, poor, pov, useless, lazy?, needy, really kewl guy, who would really really like to build an LM3886 based amplifer, using 8, THATS RIGHT!!! 8 chips... I want to do the whole active filter thing..... I am planning on using 2 bridged LM3886s for each woofer, 1 LM3886 for the mid and one for the tweet.. totaling 8.. (good at maths too) I would really, really, really, really LOVE to use PCBs with 2 ICs per board (somthing like rod elliots got) but can't afford to pay 25bux or so per PCB (I need 4, thats 100bux!!! I can get a 500VA transformer for that.. :P) HAs anyone, ANYONE designed a PCB for the LM3886, either 1 or 2 on the board.. I asked rod if I could have the board design (tracks and stuff) but he refused.. I even offered to pay!!!! no go.. so, anyone?? also, while I am here adding to my post count, where can I get a transformer from to power 8 LM3886s with +-25volts? (18volt transformer) I think 700VA should be enough.. thanx for reading this.. lol
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Old 31st December 2002, 02:28 PM   #2
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Cool... just noticed your also in Adelaide. Small world.

I guess you could have my old bridged LM3886 PCB diagram (i lost my latest design), but you still have to make the boards. If you make them yourself you can do it for under $25s each. But it will take time and effort.

You might want to look at an old copy of SlilconChip for a design of a single LM3886 board... or buy the kit from Jaycar or Dickies.

You wont be able to buy a 700VA transformer easily.
300VA and 500VAs are easy to get though (Aztronics).

BTW... please use the enter key more in your next post.. itll be easier to read then.
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Old 31st December 2002, 10:59 PM   #3
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:P the design in the silicon chip mag (the one used by Jaycar, DickSmiths and Altronics) isn't too good...

You designed a board?? Yes please.. but how small is it? I really wanted to mount 4 ICs (2 boards worth) on the one 30cm long heatsink...

I know I can get 500VA transformers from Altronics.. BUT THEY ARE $120!!! :P

Enter.. I was thinking about putting a blank line between each word.. lol
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Old 1st January 2003, 09:57 AM   #4
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Quote:
:P the design in the silicon chip mag (the one used by Jaycar, DickSmiths and Altronics) isn't too good...
Why?

Quote:
You designed a board?? Yes please.. but how small is it? I really wanted to mount 4 ICs (2 boards worth) on the one 30cm long heatsink...
I cant remeber the size.
Can you make the boards up yourself?

Quote:
I know I can get 500VA transformers from Altronics.. BUT THEY ARE $120!!! :P
Yeh... its a decent price, you cant get them for free
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Old 1st January 2003, 10:17 AM   #5
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Well, the board is HUGE (compaired to rod elliots)

Dunno if I can make my own boards, haven't tried, but would REALLY like to... can you make your own boards??

Why not?? you can get them for less than that.. I HOPE!!!
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Old 1st January 2003, 10:21 AM   #6
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If you want to go to LM3875, ( sounds better but slightly less power), I can give you a pcb layout...
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Old 1st January 2003, 10:36 AM   #7
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Well, I haven't totally decided what chip I want to use yet.....

If I could got a whole lot of designs I could chose the one most suited to me, or TRY to make my own..

I have designed many boards (never made any) most seem okay, but when I try to go a simple amp, it never LOOKS right.. perhaps I am just fussy.. :P
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Old 2nd January 2003, 12:20 AM   #8
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Actually, the LM3875 is probably better, I was using lower voltage rails anyway, which limited the power.. Also, does ANYONE have a PCB layout for the LM3886 to change a link to choose whether it is bridged or not.. I TRIED to design one, but once I have finished discovered that it was all wrong anyway.. :P
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Old 2nd January 2003, 11:06 AM   #9
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Default Gainclone pcb

Quote:
Originally posted by SkinnyBoy
Actually, the LM3875 is probably better, I was using lower voltage rails anyway, which limited the power.. Also, does ANYONE have a PCB layout for the LM3886 to change a link to choose whether it is bridged or not.. I TRIED to design one, but once I have finished discovered that it was all wrong anyway.. :P
If you have some patience. I'm gathering information to design a "universal" gainclone pcb, with slight variations for using 3875 or 3886.

The idea is to include some suggestions now going at the "gainclone site", like using trimpots to null DC offset and resistors/ccs for class-A biasing.

As I still try to keep paths short, the main problem is positioning the supply caps so they can be near the supply pins.

Suggestions to accomplish that are welcome.

I'm also trying to investigate proven ways to bridge and parallel these chips.


Carlos
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Old 2nd January 2003, 11:14 AM   #10
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I have patience.. I wait 5 minutes... If you not done, I KILL YOU!! okey?? hmm, better not say that out loud... umm, yeah, I'll wait, and see.. I don't actaully have any speakers to use the amp with yet, and even when I do get the speakers, I already have 2 amps.. I wanna do an active crossover you see..
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