Just Google "Vox AC30 schematics" or whatever your favourite amp might be. The classic guitar amp designs have all been around so long, schematics are easy to find.
I already did that but the schematics for marshall and orange amps are really unclear
A couple days ago I tore apart my old "trusty" Dean Markley K-50. It have been standing in a corner at my parents place for 10 years and when i got it back I realised that it sounded.. bad .Scratchy pots, annoying hum and crackling inputs. (hey its over 25 years old or so)
I managed to find the schematics, but I start to realize that there is some differences in the actual circuit and the shematics. Some values differs, some components is missing (as in: not even a place for them on the pcb)
so you really need access to a amp to be able to verify the design. In my case I suspect that there are 2 different revisions
rhdf : that's mostly the revision difference. In his case he wants to 'build' his own amp, ANY amp, I think.
Anyway seeing as I'm a music enthusiast and an engineer myself (and have built some amplifier back in my youth)...
First let's clarify :
1) Do you need a guitar 'amp' or do you need a guitar 'amplifier cabinet'
What's the difference you ask? it's the difference between "I want to build a car engine" and "I want to build a car"
Most of the bulk price in guitar amplifier is actually in the speaker and cabinet, how they engineer those sound box criteria and tune them for certain frequency etc etc (For example, you'll find that most Accoustic guitar will 'ring' (ie resonate) at either a low A or low E)
2) What type of amplifier, or more specifically, what kind of sound are you going after?
I shall not delve into the whole amplifier class and the whole thingamabob, but suffice to clarify if you want a more or less faithfull reproduction of your amp sound (like most solid states amplifier do) or a little bit of a 'warm and fuzzy' sound (the characteristic of a tube).
3)Will it be a stand alone amplifier (A barebone amplifier with just gain/volume control, and some crude passive tone filter for bass/mid/treble)? Or would you want a 'rocking' one with distortion/overdrive built into it and all whatever-you-want-to-whack-in (reverb, echo, 10-band eq, whathaveyou)
And... after you've pondered the 3 above clarification point, let us then look at these few points :
1) What is the extent of your knowledge in electronics?
I know jack scrap about electronics when I built my first amplifier with a crude 8-Ohm midrange 5Watt speakers and some circuitry I found on elektor, but I do know or at least I do have sufficient knowledge (from being electrocuted at the young age when I poke the live socket with a tweezer...
) to know that some parts requires playing around with mains voltage which can be quite fatal.
2) How curious are you about the working beneath, that is, do you just want a working item, or are you interested to learn in the working of the item as you built them?
3) How diligent are you in searching for an answer? (which, judging by the flow of this topic so far, is not a lot I guess)
Aaaaaand I need to stahp ranting