JoeBob
Project 4 describes a linear power supply (switches, fuses, transformer, bridge rectifiers, smoothing caps). This takes mains and makes it into two DC rails of the right value for your amps. It allows you to manually switch on and off. It will work without anything else.
However, there are two improvements you can make, which are in addition to the above:
1) Management of in-rush current on power-up to avoid lights dimming, etc and enhancing the life of your power supply. Rod's circuit does this, a triac will as well. Only needed because of the size of the power supply and use of toroids - only large commercial amps use these techniques.
2) Relay switching of power to the amp. Allows you to remote the amp power on. My very minor adaption of Rod's circuit does this, and has the side benefit of making Rod's circuit a bit safer.
As far as triacs are concerned, Rod provides the pro's and con's in his soft start documentation. AudioFreak is right to say that a triac will provide protection after power-up. The soft-start is a better way of protecting the amp every time you switch it on (often), the triac route comes into its own when things go horribly wrong or you overcook it (hopefully not often). My healthy respect for mains AC means that Rod's warnings are enough to put me off triacs, and the noise issues concern me.
If you want to do the soft start circuit, your decision is how to power the relay control circuit. Rod provides two options, but strongly recommends the former (separate transformer). You definitely shouldn't try the latter.
Having dismissed deriving the power from your main supply rails, you need to think where your 12Vdc is going to come from. One option is everything to the right of R3 (2k2) in Rod's Figure 2 circuit.
I have 12V easily available in my pre-amp, so I omit the components mentioned above. If you have an easy source of 12V, you don't need this either. The pre-amp is a good place to control the power-up of your power-amp, because it means you only have to turn everything on in one place, and the pre-amp output settles before the power amp comes on avoiding nasty pops. If your pre-amp is a commercial unit, you won't want to do this.
If you don't, an EI transformer will do the job, but I wouldn't put this in the same box as your amp modules, as they have strong stray fields which can lead to pickup. You could always just use a 12Vdc wall block (my circuit draws about 120mA) - very easy.
Because my adaptation of Rod's circuit was very basic, I didn't bother drawing it. However, I'll do this today with some block diagrams to make this easier for you to follow. I will also provide a parts list.
Let me stress the safety aspect again - if you haven't done much of this stuff before, heed all of Rod's warnings, and get your electrician friend to check particularly the mains wiring before you switch on. Always unplug before doing any work on this stuff.
