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Old 18th April 2012, 07:33 PM   #1
diyAudio Member
 
Join Date: Apr 2012
Default Anyone with any experience or technical knowledge of this PCB

Hi All,

New to the forum and I must say, the knowledge here is amazing! I wish I had known about this forum a long long time ago!

On to the topic at hand:

Does anyone have advanced knowledge of this board:

LM3886 x2 + opamp preamplifier 68W 4 ohm amplifier PCB | eBay

I have seen some folks post positive remarks about Jims Audio on Ebay and this board seems like a good fit for my application.

My speaker cabinet is a stereo cabinet with two full range speakers, so no crossovers are needed.

I already have a 28.4v secondary transformer so that is taken care of. I'll get the rest of everything else from Mouser or other known supplier.

The auction info has very little info but I was mainly wondering what the maximum input level would be. My application is not really hifi in nature so garden variety opamps will suffice like the NE5532 mentioned.

I have already built an XY Power amp and it has had some issues. Will post about that in another thread when I have the chance to get some better pictures.

Thanks in advance,

Mick
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Old 19th April 2012, 11:17 PM   #2
Minion is offline Minion  Canada
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Join Date: May 2006
Location: Cowican Bay , vancouver island
You will need a Transformer that either has 2 secondaries or is center tapped so a single 28v winding won"t do you any good .....

A dual 28v or center tapped 56v transformer will be too high of a voltage for the Chip .....
28v will get you about 42v DC which is a bit high for the LM3886 , I wouldn"t go any higher than +/-35v DC into 8 ohms or +/-28v into 4 ohms ......

I would suggest you look for a transformer that has 24v 0v 24v for an amp that drives 8 ohms or 20v 0v 20v for an amp driving 4 ohms ......

PS: the Ebay add is misleading .... first it says it runs off of a 28v 0v 28v transformer which is really the very upper limits of the chip and risks frying the chip if your house voltage spikes , and it also gives the impression that you can run it into 4 ohm loads at that voltage which is totally false , the chip can not drive 4 ohms useing a 28v 0v 28v transformer.....

Cheers

Last edited by Minion; 19th April 2012 at 11:21 PM.
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Old 20th April 2012, 03:28 PM   #3
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Join Date: Apr 2012
Quote:
Originally Posted by Minion View Post
You will need a Transformer that either has 2 secondaries or is center tapped so a single 28v winding won"t do you any good .....

A dual 28v or center tapped 56v transformer will be too high of a voltage for the Chip .....
28v will get you about 42v DC which is a bit high for the LM3886 , I wouldn"t go any higher than +/-35v DC into 8 ohms or +/-28v into 4 ohms ......

I would suggest you look for a transformer that has 24v 0v 24v for an amp that drives 8 ohms or 20v 0v 20v for an amp driving 4 ohms ......

PS: the Ebay add is misleading .... first it says it runs off of a 28v 0v 28v transformer which is really the very upper limits of the chip and risks frying the chip if your house voltage spikes , and it also gives the impression that you can run it into 4 ohm loads at that voltage which is totally false , the chip can not drive 4 ohms useing a 28v 0v 28v transformer.....

Cheers
Thanks Minion.

My apologies, I was not clear in my original post.. my current transformer is 28-0-28 and I am willing to get a 24-0-24 to help prevent the risk of toasting the amp.

As to dealing with Jims Audio... I can't say enough good things... Ordered two boards... parts list and schematic were sent shortly after... Several questions were answered quickly... I will certianly purchase from Jims Audio again!
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