You need a bucking transformer. Get a transformer with a 120VAC primary, and a 12.6VAC secondary.
Its primary goes across the AC line. Its secondary goes in series with your PSU transformer primary.
Choose the phasing of the bucking transformer's secondary winding to reduce the PSU output voltage.
The current rating of the bucking secondary winding should be the same (or more) as the PSU primary.
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You could add a simple mosfet cap Mx and drop 4v sometimes 4.5v depending on particular part, plus get -50dB ripple reduction. Perfect match for this transformer.
It will dissipate whatever current x 4v drop there is but really helps reduce power supply ripple and hum.
$4 for IRFP240 and 9240 MOSFET, a few resistors and capacitors. Under $10 total and a lot cheaper than a buck trafo or a new trafo. Plus you get ripple eater and a slow ramp up soft start.
Juma's Easy-Peasy Capacitance Multiplier
If you need another 0.5v drop add a CRC filter to clean it up even more.
It will dissipate whatever current x 4v drop there is but really helps reduce power supply ripple and hum.
$4 for IRFP240 and 9240 MOSFET, a few resistors and capacitors. Under $10 total and a lot cheaper than a buck trafo or a new trafo. Plus you get ripple eater and a slow ramp up soft start.
Juma's Easy-Peasy Capacitance Multiplier
If you need another 0.5v drop add a CRC filter to clean it up even more.
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16*20A (8 for each rail) diodes in series with the rails will drop 8*0.6V, A LM317 with a boosting transistor will also do it just for testing, but TDA datasheet tells to use 30V and not 40V.
Sometimes it is easy to unwind a couple of turns from the transformer.
Voltage And Current Regulators
Sometimes it is easy to unwind a couple of turns from the transformer.
Voltage And Current Regulators
The datasheet I'm looking at seems to indicate the top end of the range of supply voltage is 40 (see attached). I suspect I'm misinterpreting it. Please set me straight, thank you.
Certainly, and allow +/- 10% additional for that.
Any kind of capacitor derating helps with reliability and lifetime,
including temperature, voltage, ripple current.
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In my opinion, the best solution would be #3. As new transformers usually aren't that cheap, the 2nd best solution form #3 comes into mind. I'd modify it, though: Arrange the supplementary transformer as a real autoformer, i.e. connect the 120V primary in series with the 12V secondary, observing the right phase. Then connect the amplifier's tranny to the 120V and mains power to the ends (132V).
The supplementary xformer's wattage may be much smaller than the amp's maximum power consumption - only one tenth of it in this case.
Best regards!
The supplementary xformer's wattage may be much smaller than the amp's maximum power consumption - only one tenth of it in this case.
Best regards!
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