One good way to go may be using a fairly large toroidal transformer.. something like this:
[www.mouser.com]
followed by a bridge rectifier and large capacitor. After this basic circuit, you can build your own regulation circuit with 3 transistors, an op amp, voltage regulator (for op amp), and some passives (I attached a circuit that has worked well for me). You can output much greater current than using LM338s. Technically you can parallel LM338s to increase the current capabilities, but I have found this is much more difficult in practice than just building your own regulator circuit with a beefy power transistor.
One thing you should be aware of is that a 12V rated output transformer when hooked up to a bridge rectifier/capactor will be more like 17V when unloaded and will approach 12V as you increase the load. Also, when you increase the load, unless you are using huge capacitors, you will start to get a 120hz ripple (if using 60hz AC). This may or may not be a problem, but you should be aware of it.
The circuit I attached would be good for you if you plan on running a fixed voltage that is close to the transformer rated voltage. The output voltage is adjustable, but may be impractical to run too low of voltage at high power. You will dissipate heat relative to your dropout voltage, but the good thing is that the dropout voltage decreases as the load increases. For example, let's say you are pulling 1 amp at 12 volts and at this load, the output of your bridge rectifier/filter circuit (input to regulator circuit) is 17V.. In this scenario, you would be dissipating 5 Watts ((17v-12v) * 1a = 5w) of heat. Then let's say you pull 10 amps again at 12 volts. At this load you wouldn't be dissipating 50 Watts ((17v-12v) * 10a = 50w) of heat. Instead, the bridge rectifier/filter circuit would be outputting more like 14 volts, which translates to dissipating 20 Watts ((14v-12v) * 10a = 20w) of heat.
One good thing is that the output voltage is SUPER clean and it is a relatively simple and robust circuit. It is also really quiet (no switching noises). The negative is that it is expensive and it might not be powerful enough to run your whole 3D printer (depends on your heated bed situation). The transformer is about $80 and the large capacitor is around $10, but one would say that the education gained from such a project is.. priceless..
[www.mouser.com]
followed by a bridge rectifier and large capacitor. After this basic circuit, you can build your own regulation circuit with 3 transistors, an op amp, voltage regulator (for op amp), and some passives (I attached a circuit that has worked well for me). You can output much greater current than using LM338s. Technically you can parallel LM338s to increase the current capabilities, but I have found this is much more difficult in practice than just building your own regulator circuit with a beefy power transistor.
One thing you should be aware of is that a 12V rated output transformer when hooked up to a bridge rectifier/capactor will be more like 17V when unloaded and will approach 12V as you increase the load. Also, when you increase the load, unless you are using huge capacitors, you will start to get a 120hz ripple (if using 60hz AC). This may or may not be a problem, but you should be aware of it.
The circuit I attached would be good for you if you plan on running a fixed voltage that is close to the transformer rated voltage. The output voltage is adjustable, but may be impractical to run too low of voltage at high power. You will dissipate heat relative to your dropout voltage, but the good thing is that the dropout voltage decreases as the load increases. For example, let's say you are pulling 1 amp at 12 volts and at this load, the output of your bridge rectifier/filter circuit (input to regulator circuit) is 17V.. In this scenario, you would be dissipating 5 Watts ((17v-12v) * 1a = 5w) of heat. Then let's say you pull 10 amps again at 12 volts. At this load you wouldn't be dissipating 50 Watts ((17v-12v) * 10a = 50w) of heat. Instead, the bridge rectifier/filter circuit would be outputting more like 14 volts, which translates to dissipating 20 Watts ((14v-12v) * 10a = 20w) of heat.
One good thing is that the output voltage is SUPER clean and it is a relatively simple and robust circuit. It is also really quiet (no switching noises). The negative is that it is expensive and it might not be powerful enough to run your whole 3D printer (depends on your heated bed situation). The transformer is about $80 and the large capacitor is around $10, but one would say that the education gained from such a project is.. priceless..