Question about transformer for the TDA7294amp

swen_blueneon · 5th July 2007, 04:31 PM

hello...i was wondering what will happen if i use 2*30V / 5A toroidal transformer for the TDA7294 amp..becouse in the schematics it says that we need transformer (xxVA) CENTRE TAPPED....well this is the problem...can I use my toroidal or I must buy C.T. transformer??
tnx

here are the schematics

AndrewT · 5th July 2007, 05:08 PM

Hi,
your twin secondary can be converted to a centre tapped by joining the two windings in series.

swen_blueneon · 5th July 2007, 05:37 PM

ok...and the I get something like +30V 0 -30V ??

and what current do I get now.... 5A + 5A or just 5A...but 60V ?

AndrewT · 6th July 2007, 08:18 AM

Hi,
don't worry about the current. You have selected the transformer size based on VA rating and this is adequate.

BTW,
the VA rating should be between 1*maxmimum power output to 1.6* max power for classAB amplifiers. ClassA amplifiers need quite a bit more between 3*max power to 6*max power.

Your selected transformer is 30+30 * 5=300VA, this is ideal for a total power output of 200W or 100W +100W for a two channel amplifier.

A 30-0-30Vac or 30-0 & 30-0Vac transformer with a rectifier and capacitor input filter will give about +-44Vdc. You are in the chipamp Forum, will your chipamp survive this voltage?
If the mains input rises to maximum tolerance then @ +6% the PSU will send almost +-47Vdc to the amplifier.

swen_blueneon · 6th July 2007, 05:49 PM

ok TNX

I'm trying to use TDA 7294....it operates on +/-50V
I thik it will survive..

becouse the trafnsformer is from antother chip amp...TIP142 + TIP147...(200W music power_100W RMS)

AndrewT · 7th July 2007, 07:31 AM

Hi,
TDA7294 spec says
+-50Vdc no signal
+-40Vdc max operating

Your transformer is for a 100W into 8ohm amplifier, this chip is not that.

swen_blueneon · 7th July 2007, 12:29 PM

ok....
thank you very much for the information...

funky2x · 16th June 2008, 06:22 AM

I use 2 center taped transformer 12x2 connecting them in series
24x2 =48

Minion · 17th June 2008, 03:28 PM

If you try the TDA7293 Chip (pretty much the same as the TDA7294) it can handle +/-50V (+/-60v No Signal) ....The chip should also cost the same and work in the same PCB...

Cheers

Hosam · 10th February 2011, 02:49 AM

well as you mention double transformers 12x2 how I should connect them to get 48v?

5th July 2007, 05:08 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, your twin secondary can be converted to a centre tapped by joining the two windings in series. __________________ regards Andrew T.

6th July 2007, 08:18 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, don't worry about the current. You have selected the transformer size based on VA rating and this is adequate. BTW, the VA rating should be between 1maxmimum power output to 1.6 max power for classAB amplifiers. ClassA amplifiers need quite a bit more between 3max power to 6max power. Your selected transformer is 30+30 * 5=300VA, this is ideal for a total power output of 200W or 100W +100W for a two channel amplifier. A 30-0-30Vac or 30-0 & 30-0Vac transformer with a rectifier and capacitor input filter will give about +-44Vdc. You are in the chipamp Forum, will your chipamp survive this voltage? If the mains input rises to maximum tolerance then @ +6% the PSU will send almost +-47Vdc to the amplifier. __________________ regards Andrew T.

7th July 2007, 07:31 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, TDA7294 spec says +-50Vdc no signal +-40Vdc max operating Your transformer is for a 100W into 8ohm amplifier, this chip is not that. __________________ regards Andrew T.

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5th July 2007, 05:37 PM	#3
swen_blueneon diyAudio Member Join Date: May 2007	ok...and the I get something like +30V 0 -30V ?? and what current do I get now.... 5A + 5A or just 5A...but 60V ?

6th July 2007, 05:49 PM	#5
swen_blueneon diyAudio Member Join Date: May 2007	ok TNX I'm trying to use TDA 7294....it operates on +/-50V I thik it will survive.. becouse the trafnsformer is from antother chip amp...TIP142 + TIP147...(200W music power_100W RMS)

7th July 2007, 12:29 PM	#7
swen_blueneon diyAudio Member Join Date: May 2007	ok.... thank you very much for the information...

16th June 2008, 06:22 AM	#8
funky2x diyAudio Member Join Date: Jan 2008	I use 2 center taped transformer 12x2 connecting them in series 24x2 =48

17th June 2008, 03:28 PM	#9
Minion diyAudio Member Join Date: May 2006	If you try the TDA7293 Chip (pretty much the same as the TDA7294) it can handle +/-50V (+/-60v No Signal) ....The chip should also cost the same and work in the same PCB... Cheers

10th February 2011, 02:49 AM	#10
Hosam diyAudio Member Join Date: Jan 2011 Location: Syria - Canada	well as you mention double transformers 12x2 how I should connect them to get 48v?

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