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Old 11th April 2005, 09:37 PM   #1
blip is offline blip  United States
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Default Dual CT Transformers with LM3886?

Hi,

I've been planning on building a BrianGT LM3886 for my father... The one hook I've become tripped up on is finding an affordable transformer.

What I was wondering is can I use two center-tapped 24v 5a transformers in the same way that you would use a transformer with dual-secondaries? I can get them for fairly cheap.

Any better suggestions?
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Old 12th April 2005, 04:21 AM   #2
homer09 is offline homer09  Canada
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this topic has been overkilled in this forum. please please search
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Old 12th April 2005, 07:04 AM   #3
steenoe is offline steenoe  Denmark
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Quote:
can I use two center-tapped 24v 5a transformers in the same way that you would use a transformer with dual-secondaries?
Yes, you can. Just don't connect the centertap anywhere. Good luck.

Steen.
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Old 12th April 2005, 07:06 AM   #4
blip is offline blip  United States
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I did search but I'm still a bit confused as to whether or not two center tapped transformers can be used in this configuration.

From my (rather minor) understanding of electrical theory it should... But I'm basically just doing a quick error check in my thinking.

Edit: Just saw Steeno's post thanks for the answer... I owe ya.
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Old 12th April 2005, 07:49 AM   #5
ll81 is offline ll81  United Kingdom
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I just built an amp using dual transformers with singal outputs in series. The rails differ slightly in voltage. It should work although the transformers will be worked hard if the amp is running flat out. Also check the output voltages match otherwise one transformer will be workrd harder than the other.
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Old 12th April 2005, 08:53 AM   #6
Nuuk is offline Nuuk  United Kingdom
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I suspect the results would be better using one transformer for each channel!
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Old 12th April 2005, 07:33 PM   #7
blip is offline blip  United States
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Quote:
Originally posted by Nuuk
I suspect the results would be better using one transformer for each channel!

Really? I thought +/-12v was awefully low for LM3886... Maybe I mis-read the data sheet. That would certainly make my life easier!

Anyway, in the end, I may just pick up a toriod from Parts Express (they seem to have the best prices for the US).... It may be worth it instead of messing around with these transformers.
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Old 12th April 2005, 07:43 PM   #8
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If you carefully reread Steenoe's msg he says to ignore CT; this will give you +/- 25 volts not 12.5. You simply treat each secondary winding as if you have a single transformer with 2 secondary windings. you will not use the centre taps at all, no connection to the CTs.
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Old 12th April 2005, 10:16 PM   #9
Nuuk is offline Nuuk  United Kingdom
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Quote:
Really? I thought +/-12v was awefully low for LM3886...
Yes, sorry, I forgot you want to use a 3886!
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Old 13th April 2005, 01:35 AM   #10
blip is offline blip  United States
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Quote:
Originally posted by Nuuk


Yes, sorry, I forgot you want to use a 3886!
Not a problem. I'm going to check in with my dad again about his power requirements... Maybe the LM3875 would serve just fine. (If I recall the LM3875 sheet, +/- 12v should be okay, right?)
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