TDA7293 Amplification board design (Need advice)

Mrmax1n

Member
2020-01-30 8:17 am
Hi everyone! I'm making my Hi-fi sound system project, and after finishing the power supply board and tested it, I'm designing the power amplification board. Any advice on the placement/routing before I print the board?


I'm using 2 TDA7293, supplied by a +/-40V power supply. The Transformer used in the power supply is a 80VA one?


About the routing;

the top layer is mostly for audio signal and the bottom for power signal.
Top layer :
Dark green and Red : audio output (speakers)
Light green and dark blue : audio input
Orange : command signal for Mute/Stand by function

The top layer also has a "polygon pour" (don't remember the word sorry) connected to nothing, to reduce noise.

Bottom layer :
Pink and light blue : power supply
white : Ground
 

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PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
The target output power is 50W...

So 2*50W is 100 Watts audio rating?

There is loss from DC to sine (the way we rate) audio. 100 Watts output may want 150 Watts DC. And +/-40V promises 90+ watts in 8 ohms, so 180W of audio wants like 270W of DC.

There is strain in AC to DC conversion. The transformer VA should be picked significantly larger than the DC you need. A number like 1.3 is a good pencil guess. So as much as 347VA of iron.

But that supports all-day FULL power. Speech/music at clipping averages like 1/10th power. Amplifier loss as a fraction of output goes up, you can't run 35VA. 100VA to 120VA would be used in a "popular price" receiver of the 1970s, and it would play well, but not truly "solid" dynamics.

All of these will work. It's your amp,, do what you want. I'd suspect the 35VA is woefully inadequate for even mildly loud use (use the same core much much lower voltage and lower power expectation). A 400VA will measure great on test tones. 120VA to 250V seem like reasonable picks for most folks.
 

Mrmax1n

Member
2020-01-30 8:17 am
So 2*50W is 100 Watts audio rating?

There is loss from DC to sine (the way we rate) audio. 100 Watts output may want 150 Watts DC. And +/-40V promises 90+ watts in 8 ohms, so 180W of audio wants like 270W of DC.

There is strain in AC to DC conversion. The transformer VA should be picked significantly larger than the DC you need. A number like 1.3 is a good pencil guess. So as much as 347VA of iron.

But that supports all-day FULL power. Speech/music at clipping averages like 1/10th power. Amplifier loss as a fraction of output goes up, you can't run 35VA. 100VA to 120VA would be used in a "popular price" receiver of the 1970s, and it would play well, but not truly "solid" dynamics.

All of these will work. It's your amp,, do what you want. I'd suspect the 35VA is woefully inadequate for even mildly loud use (use the same core much much lower voltage and lower power expectation). A 400VA will measure great on test tones. 120VA to 250V seem like reasonable picks for most folks.

Thank you very much for your answer ! I'll re-design the power supply for at least 160VA to 200VA. I just remembered a mistake I've made when designing the power suppy, I forgot the fact that I use two TDA7293 and so I had to double the power.

Any thoughts about the layout of the amplification board ?