Dual CT Transformers with LM3886?

blip · 11th April 2005, 08:37 PM

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?

homer09 · 12th April 2005, 03:21 AM

this topic has been overkilled in this forum. please please search

steenoe · 12th April 2005, 06:04 AM

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.

blip · 12th April 2005, 06:06 AM

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.

ll81 · 12th April 2005, 06:49 AM

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.

Nuuk · 12th April 2005, 07:53 AM

I suspect the results would be better using one transformer for each channel!

blip · 12th April 2005, 06:33 PM

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.

SheldonD · 12th April 2005, 06:43 PM

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.

Nuuk · 12th April 2005, 09:16 PM

Quote:

Really? I thought +/-12v was awefully low for LM3886...

Yes, sorry, I forgot you want to use a 3886!

blip · 13th April 2005, 12:35 AM

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?)

11th April 2005, 08:37 PM	#1
blip diyAudio Member Join Date: Mar 2003 Location: Salem, OR	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?

12th April 2005, 03:21 AM	#2
homer09 diyAudio Member Join Date: Jan 2004 Location: Montreal	this topic has been overkilled in this forum. please please search __________________ Most people wouldn't know good music if it came up and bit them in the ***. - Frank Zappa

12th April 2005, 07:53 AM	#6
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	I suspect the results would be better using one transformer for each channel! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

12th April 2005, 06:43 PM	#8
SheldonD diyAudio Member Join Date: Feb 2004 Location: North of Toronto	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. __________________ Sheldon D

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12th April 2005, 06:06 AM	#4
blip diyAudio Member Join Date: Mar 2003 Location: Salem, OR	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.

12th April 2005, 06:49 AM	#5
ll81 diyAudio Member Join Date: Apr 2005 Location: lincolnshire	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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