Thank you for clarifying, I haven't decided which pre-amp to use, I have 4558, TL072 and some transistor design. After building the power amp I'll just mix and match what sound my brother wants.

I want to build a small amp for my brother. I made this diagram using a TDA2030, my problem is my design requires a bi-polar power supply to power my TDA2030, since I only have a 220v-12v transformer would my design work, I also intend on adding a 9V PS to power my pre-amp.http://i.imgur.com/KBGaJ.jpg  if this design works, what are the disadvantages of such design. Thank you  :tu:

thanks for the quick response.. 

i have some question here, would be glad if all of them will be answered.

1.for example I have 2 amplifiers one is a 50w in a 2x12 stack the other is a 30w connected to a 4x12, which will be louder? and why?

2.How critical is the sound on the size of a cabinet? for example a 4x12 marshall, what would happen if i increase or decrease the size proportionally of the cabinet, would it affect the tone?

3.if a guitar head say it allows 8ohms and i plug a cabinet that is more than the specified, would it affect the loudness?

4.has there been a amp head where you can hook up multiple cabinets?

misc question-->is it possible to run 2 or more pre-amps through one power amp? if yes, then what are some of the thing that should be considered?

thanks for the help.. 8|.. About cabinet construction, what are the dimensions of an upright 2x12 stack? can anyone give a generic dimension? what is the best material for enclosing the circuits? can a GI sheet be used? what are the pros and cons of each material used in amp head enclosure..thanks for the help in advance.

thanks for that information, so therefore power amps in SS amps is basically a power amp, while in tube amps, they can add color to the amps sound.. now i can push through with my work.. thanks for the help..  :tu:

  thanks for the help, i can manage building complex circuits i kinda' like designing PCB's.. does different design on power amp change the amps sound dramatically or just a subtle change can occur on sound.. if it does change the sound, i think i'll build 2 different power amplifiers..

hello, i need an opinion about this, i have started to build both a guitar and bass amp, well i have finished the preamp section for both, my problem now is the power amp, my guitar amp should be around 50-75w and my bass could be 100-150w.
would the power amp section of this design be good for bass,  http://sound.westhost.com/project27.htm, i have heard good feed backs on this project for guitar, not sure about the bass.... i'm more concerned on the power-amp section..
and can someone explain the difference between the speakers used in guitar amps and bass amps? :duh
thanks for any input in advance. :tu: