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Old 23rd June 2004, 02:42 AM   #1
Tim__x is offline Tim__x  Canada
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Question Bridge+Parallel LM3886, Doable?

I want to build a bridged LM3886 based amp for use with 8/4 and yes even 2 ohm loads. I already have a suitable 20-0-20 transformer.

What I'm thinking is a standard configuration with four IC's, two in parallel per a side. Would this be sufficient? Maximum peak current would be slightly under 10 amps an IC, I'm thinking I would use a rather large heatsink with a temp controlled fan.
Would this work? Or should I use three IC's a side?
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Old 23rd June 2004, 04:34 AM   #2
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Tim,
4 chips will work out fine.
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Old 23rd June 2004, 05:49 AM   #3
Tim__x is offline Tim__x  Canada
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Thanks, I had seen that example from the datasheet before, but thank-you anyway.

Really what I'm asking is would it be safe with two ohm loads?
I guess I didn't really make that clear before, sorry 'bout that.
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Old 23rd June 2004, 07:56 AM   #4
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Have you checked Thomas madsen's pcb?
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Old 23rd June 2004, 09:17 AM   #5
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Hi Tim

I think that you are "pushing it" with a 2 ohm load for a bridge/parellel config. Remember that each arm only see ½-load, this means 1 ohm. Since each arm are two chips in parallel they see 2x load, this means that each chip sees 2 ohm !!!!!!!!!!
It does help with the "lower" voltage you have, but I still think it is "pushing it".
Either you can put more chips in each arm OR make a parallel config with your 4 chips (this will "limit" your power in 8 ohm), but make it fly for 2 ohm load.

Have fun

Thomas
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Old 23rd June 2004, 09:35 AM   #6
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I wonder, do you have two 4 ohms speaker in parallel or four 8 ohms in parallel? Maybe it's better to build two amps
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Old 23rd June 2004, 05:32 PM   #7
Tim__x is offline Tim__x  Canada
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Thank you all for your help. I knew it would be pushing it, but I wanted to know exactly how much it would be pushing it.
I think I will go for 6 IC's, 3 a side with very hefty heat-sinking.
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