I am working on an amplifier that requires a 30V 10amp DC power supply. I want to build this myself to house the converter from 120V wall AC to DC inside of the speaker's chassis itself, mostly to avoid ugly power bricks. My initial design runs AC power from an IEC port (with integrated fuse) through a simple on/off toggle switch, then to a Hammond 265S24 24V transformer. The 24V, 10amp AC signal is then rectified using a Navitas KBPC3506W bridge rectifier, which I believe will produce a fluctuating DC signal peaking at ~33V. This is smoothed a bit using 3 EGPD500ELL302MM35H aluminum electrolytic capacitors (3000uF, rated at 50V each) in parallel to spread the 10amp load, then sent to a custom LDO linear regulator with a TIP147 PNP transistor and an LM431 regulator IC providing a stable 30V reference voltage (resistors are 1k ohm and 11k ohm to dial this in). I believe this should output a pretty stable 30V 10amp DC current, which I will also pass through a few more parallel capacitors on the input end of my project PCB, but I would really like more eyes on this! 
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\$\begingroup\$ Welcome! Have you simulated your circuit? \$\endgroup\$winny– winny2026-07-01 07:27:51 +00:00Commented 12 hours ago
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\$\begingroup\$ It's wrong! You better get some working example, kit ,... it won't work with guessing - it will burn. Your schematisc is a big zener diode, not a LDO. \$\endgroup\$Marko Buršič– Marko Buršič2026-07-01 07:29:41 +00:00Commented 12 hours ago
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\$\begingroup\$ Please don't draw rectifiers like this, it is confusing. Use the standard schematic symbol with all diodes tilted at 45° angles. \$\endgroup\$Lundin– Lundin2026-07-01 07:50:26 +00:00Commented 12 hours ago
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4\$\begingroup\$ @Lundin That's the perfect way to draw diode rectifiers. Especially when you need to add a third phase, or an H bridge, or DC-link capacitors, or want to adjust the height of the rail or ground in a simulator's schematic editor. I'd quarrel with the wires going off left rather than right though. \$\endgroup\$Neil_UK– Neil_UK2026-07-01 08:57:16 +00:00Commented 11 hours ago
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\$\begingroup\$ @Neil_UK At least this fooled me first, thinking the DC ground was in the wrong place. Maybe it is mostly a matter of what you are used to. \$\endgroup\$Lundin– Lundin2026-07-01 08:59:23 +00:00Commented 11 hours ago
1 Answer 1
Frame challenge.
For an audio amplifier, you can usually stop at the large electrolytics (aka FBCs or Fairly Big Capacitors). There is no point in over-designing the power supply. Remember that the cheapest and most reliable components are the ones you don't fit.
Most amplifiers have a sufficiently good PSSR (Power Supply Rejection Ratio) that the ripple left on the FBCs is not audible at the output. They are designed to work with and reject this ripple.
This sort of supply has the feature (not bug) that it allows a higher instantaneous voltage for music peaks, but sags a little for extended testing at full power, so reducing the amplifier dissipation if you test it like that.
If you also want the supply to double as a general purpose power supply, then by all means add the regulators at the end. But for an amplifier, they will just waste power and drop voltage.
Having looked at your diagram more closely, you appear to have tried to implement a power shunt regulator. Without even looking at component values or topology, this is WRONG for a power supply. Shunt regulators are for very low power use only. Without a well defined series resistance before the shunt, it's not even a design, though in practice the transformer regulation and diode residual series resistance will provide that, though not well defined. Do you really want your supply + regulator to be sat there dissipating 300+ watts at zero output? As Chief Brody didn't say, "you're going to need a bigger shunt transistor and heatsink". You should use a series regulator to control the output voltage of a power supply.
As @mike points out, as you have a transformer centre tap, you could return your FBCs to that, and get a balanced power supply, for little extra cost.
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1\$\begingroup\$ Given you have a centre tapped transformer, if you do not use a regulator and you have a single ended amplifier you can also drop the output capacitor in your amplifier and use this as an unregulated +/- 15*1.414 - 2 * diode_drop= approx +/- 20 volt supply by using the centre tap as ground for the speaker. Which will almost double the PEP of your amplifier. If your amplifier is based on a bridge output, unregulated +40V will give an almost doubling of the power.. \$\endgroup\$mike james– mike james2026-07-01 09:14:54 +00:00Commented 10 hours ago
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\$\begingroup\$ I genuinely don't understand the "it's ok to drop the regulators" comment. Back when I was doing this (about 40 years ago) you wanted anything that possibly had a 50Hz ripple (obviously 60Hz in the US) kept well away from eg preamp inputs, to the extent I had a torroidal transformer and huge electrolytics (plus tantalums) in a faraday cage in one corner of the unit. I am pretty sure we used linear regulators with massive heat sinks at least for the low voltage part of the supply but I believe for the higher voltage side too (this was when linear regulators were pretty much the only option)... \$\endgroup\$abligh– abligh2026-07-01 17:27:21 +00:00Commented 2 hours ago
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\$\begingroup\$ ... was this all a huge waste of time and it would have been OK to feed the amp (IIRC class AB transistor) with unregulated power? \$\endgroup\$abligh– abligh2026-07-01 17:28:18 +00:00Commented 2 hours ago
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\$\begingroup\$ (@abligh: depends. Go to some lengths to keep supply noise low for anything with considerable voltage gain to follow. If keeping with a mains frequency transformer (Why? (OTOH, why not class D?)), voltage regulated power for the high current stage is detrimental as per above answer.)(BTW: 100/120 Hz ripple with any decent rectifier) \$\endgroup\$greybeard– greybeard2026-07-01 17:47:27 +00:00Commented 2 hours ago