Minimum voltage for the tda7293 is 12v. It's going to be anemic under 15v and the peak current is 10A, so you really want as high a voltage as you can find to ensure it runs efficiently.
As long as everything else on the board supports it, I would up the capacitor voltage. Those look like SC caps anyway which are mediocre. Quality 3300uF/40V/105Deg caps will only set you back $5 each. Well worth the upgrade. Then you can run a 24V or 30V transformer output.
https://www.st.com/resource/en/datasheet/tda7293.pdf
As long as everything else on the board supports it, I would up the capacitor voltage. Those look like SC caps anyway which are mediocre. Quality 3300uF/40V/105Deg caps will only set you back $5 each. Well worth the upgrade. Then you can run a 24V or 30V transformer output.
https://www.st.com/resource/en/datasheet/tda7293.pdf
I tried to explain this before ... coming out of the rectifier/filter cap filter is a DC voltage that gets less ripple the more you do to it, more caps - voltage regulators. With all that bundled onto this board it's far from idea - but its there for you to play with. AC is + and - its a wave that crosses from + to 0 to -. The rectifier sends the + half of the wave to the + rail (positive side of the capacitor) and - half to the negative rail (negative side of capacitor - or ground). Then the negative side caps + side goes to ground because effectively ground is positive relative to negative voltage. You are just putting the board together but its good to know that or you might doubt something.
Since the 15-0-15 transformer is for making dual rail power it may seem like is giving negative on one lead but its not. Its just that it is giving positive and negative on both AC outs and the more I try to explain it simply the more it may get obscured. THe center tap is a bit akin the the neutral - because AC, even though it flows back and forth - which is all + and - means, flow direction, needs ground to flow to in a relative way.
Diodes reject voltage that goes against it - a backwards bias of a diode actually lets backwards flowing voltage through because that means positive. So 2 diodes are forward biased to the positive rail and 2 diodes are negative biased to the negative rail. The capacitors fill the spaces by discharging when voltage drops below where-ever they are charged to which is Vpeak. Vpeak is well higher than V-rms that you measure in AC with a meter.
All that good rectifier DC filter action happens before the power is ready to bias the amplifier via it's power rails. If you build a power supply you'll know what you are looking at on this board. Also note the guy asking for the board info - you need a big *** heatsink for a amp chip that can make 100w
Ok so it looks like I’m going to be going with and purchasing two 200va 24-0–24 toroidal transformers from Antek. Thank you signal loss for leading me that way. From what I’ve gathered and tried to try and understand from everyone’s post’s it seems that these will be enough to power the tda7293’s as a single mono amp each. Please correct me if I’m wrong and should look into more or less power. Like I said I’m not looking for massive power or volume. I just wanna to be able to power the amplifiers safely and with a decent load as to raise the roof here and there. Thanks for everyone’s info!
Yeah, you should be fine with that ... but if you end up with power regulators some of them can't deal with the peak voltage of a 24v (24v AC rms = 33.936 Vp DC) so well. Your power filter is all on this board but one day you might buy another board without the rectifier part so you can build really nice power filters and run the same chip amps.
You certainly won't get saggy voltage with your amp - stable. You will get a big current inrush with those toroidal transformers ... so that's another thing to research. I put these NTC thermistors on one of the AC inputs to the transistor to slow the inrush on cold start. I put a fuse on the other one, some put a fuse on both AC links to each transformer. I doubt there are fuses on your amplifier board.
Dealing with Inrush Currents for Toroidal Transformers - Toroids - Torelco.com
You certainly won't get saggy voltage with your amp - stable. You will get a big current inrush with those toroidal transformers ... so that's another thing to research. I put these NTC thermistors on one of the AC inputs to the transistor to slow the inrush on cold start. I put a fuse on the other one, some put a fuse on both AC links to each transformer. I doubt there are fuses on your amplifier board.
Dealing with Inrush Currents for Toroidal Transformers - Toroids - Torelco.com
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With 24V secondaries those 200va units will be plenty of input power to play that board loud. How it holds up to playing loud will depend on your heat sinks and controlling power up and power down. On my first watt clones I have used CL60 thermisters to control inrush current, but for my Dibya Christmas amp I am going to use a softstart board by Mark Johnson that allows for a low voltage switch to power on the amp. It would be wise to use something to control inrush current.
Secondly you may want to consider your next amp when you purchase the transformers. Many LM3886 amps and first watt amps use 18v secondaries. Some use 20v secondaries. I was able to get the board to play loud into a small speaker with only 12v secondaries. Just a thought. My loud may be much different from your loud.
Secondly you may want to consider your next amp when you purchase the transformers. Many LM3886 amps and first watt amps use 18v secondaries. Some use 20v secondaries. I was able to get the board to play loud into a small speaker with only 12v secondaries. Just a thought. My loud may be much different from your loud.
Wow, good info. So will the 25-0-25 transformer work for 4 ohm speaker? Or is there an ideal voltage?
I have 9 of the TDA7293s, RELIABLE ONES, and was going to toy with them. But these are populated and a good price for two, hopefully reliable. I will order the transformer then boards, make sure no harmful DC to speakers, and test. If bad, AMAZON is great on returns.
I ordered a wah-wah pedal for my guitar, had a scratch on the pedal top, not shipping damage. Told AMAZON, had a good account and the guy refunded my $140 and said keep the pedal.
Thanks for any help!