Need a power transformer for this audio amp?

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I bought a ‘100W TDA7294 Mono Audio Power Amplifier Board KA5532’ to replace a subwoofer amp that died. Apparently the seller knows nothing about the specs or what power transformer should be used other than ‘Operating Voltage: 28V +0 +28 V (AC)’. No info regarding VA or amperage values.
I assume that this reference is to a 28ct VAC power transformer offered by Hammond Manufacturing in the link I am providing? I have posted a schematic of the amp in case that holds any clues on the power transformer I am looking for.

https://www.hammfg.com/part/187F28?referer=1055
 

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the 100VA 28-0-28Vac EI transformer is likely to have quite a high transformer regulation. Maybe between 10% and 15%.
That will raise the quiescent voltage to quite a bit higher than you might expect. and give a big droop/sag in supply voltage when the amplifier is delivering near full power.

What total maximum power are you expecting from your build?
add on 50% and use that as a guide to your required VA.
 
The amp that died was a 100 watt amp. I did intend to reuse the transformer from the old amp to power the new amp module. The transformer is a 56vac center tapped transformer commonly referred to as a 28v-0-28v. The amp module seemed to be a likely candidate for this job.
I got the amp module installed and powered up. The speaker was making a static/buzzing noise and I noticed that the heat sink tab on the TDA7294 IC was at 100F and climbing fast. Also the buzzing noise seemed to get louder as the heat on the chip increased. I shut it down at 140F. Not sure what was amiss, I unhooked the 4ohm speaker I was using and hooked up an 8ohm load. This time the buzzing noise was half as loud but the heat on the chip increased like the first test so I shut down till I could get this figured out.
What I suspect is that the transformer I am attempting to use is pushing too much voltage into the amp module than is required to run it. Hence the buzzing noise from the speaker.
Going back to the original amp schematic,(in the first picture) it shows a 28V source resulting in 15VDC supply rails.
In the second picture is a suggested power supply for the TDA7294 IC (courtesy of Quasar Electronics) which shows a 50V 80VA center tapped transformer (+/- 25V AC) which results in 35VDC rails.
If I take into account the specs in the original schematic, my guess is the designers of this amp module are calling for a 28V center tapped transformer that results in (+/- 14V AC).
The transformer I posted the link to at Hammond Manufacturing seems to reflect voltage values that I am looking for here(picture 3).
Also I am attempting to use the original amp plate and the is no room for a toroidal transformer. Thanks for all the responses, and help trying to resolve this as well!
 

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Hi,

In your 1st diagram your totally missing the point, note +Vcc and
-Vcc. The 15V rails are for the op-amps, not the power amplifier.

No you do not want a 28V centre tapped transformer, that is wrong.
Your old transformer should work, perhaps a little high for 4ohm load.

rgds, sreten.

I presume you've reused the heatsink from the old amplifier too.
 
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The amp that died was a 100 watt amp. I did intend to reuse the transformer from the old amp to power the new amp module. The transformer is a 56vac center tapped transformer commonly referred to as a 28v-0-28v. .............
disconnect the transformer and test it. If it passes, then reuse it.
It should be ideal for a 100W into 4ohms mono, or 60+60W into 8+8ohms stereo amplifier.
 
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