Thanks for that Roly, I've currently got the amp working using the design I've attached to this post. It works quite well but obviously I don't have a tone control. I'm taking the amp to band practice with me tonight to test it and will know then if I definitely like the sound. Although I may adopt your design anyway!

With regards to having the 4.7K Source Resistor as a 5K Pot, isn't this bad?

O by the way since I put the tone control back in the bass response as gone down slightly which is nice, but I won't know for sure until tonight when I can actually give the amp a proper going through. Also I used a 1uF Solid Tantulum in the end as the 100N Cap I tried didn't make any difference whatsoever to the tone which is odd, unless its because I'm using a 5K Pot!

Spot on Enzo. I don't believe in saying an amp is good or bad, it all depends on the person's taste.

Added a tone control in and now it sounds pretty sweet at all volumes, I'll upload an updated schematic another day as its 22:30 here. I'm going to give the amp a proper test at band practice tomorrow night before I say its finished, may not be loud enough yet. I want to use this as my backup amp at gigs

You are right with regards to the 100K pot becoming a volume control, however now that I've removed the diodes the overdrive sounds great. Only quarrel I have with it is the amount of bass at lower volumes, so I was thinking of removing the 100K pot and then putting my tone control back in (only have two holes for ports on the case). A gain control would be nicer obviously but can't work out why that 100K pot wouldn't work properly.

Ok firstly I changed the collector resistor on the BJT from 1.8K (all I have at the moment) to 1K and this just caused the same distortion effect I get when I turn down the 100K pot. So I changed it back to 1.8K and all is well again (except for the pot issue). I then changed the collector resistor on the JFET from 27K to 22K and wow what a difference. Plenty of overdrive which sounds great for single notes but not too great for chords. Now I'm getting 12.5 watts out of it which sounds great! Next thing to try is removing the two diodes on the BJT to see what effect this has, may even fix the pot issue I'm guessing?

Also when I say distort its almost unrecognizable, as if a transistor is just being pushed stupidly hard.

Well no its correct because the volume does decrease, it just seems to distort even more. Very weird. Also I don't think the preamp is driving the power amp hard enough, as after the 1.5K resistor I've only got 18volts, whereas I designed the preamp to be run on 24volts. So may change the collector resistors for slightly lower values. Also I'll probably remove the 22k resistor just above the two diodes as its doing nothing

Ok gate resistor is now 1M, this has helped however the output still isn't as good as I would like it to be, also the sound wasn't great. So I upped the voltage coming from the PSU to 26 volts and it started to sound better tone wise. Now I measured the output voltage and it reached 8 volts at the most, which divided by 8ohms (speaker cab) gives us 1 amp, multiplied by 8 gives us 8 watts so maybe I should increase the voltage further to get a bit more volume? I know this is a crude way of measuring it but its the best I can do with the tools I have.

Also when I turn down the 100k pot even just a tiny bit from max the sound starts distorting badly, I'm guessing a larger pot is required? Turning down the 10K pot does what it should and just decreases the volume.

Also the distortion is a bit harsh so perhaps I should try different diodes on the BJT? Its also slightly too bassy so I'm going to try decreasing the resistor in series with the input to help with that.

Apart from that the blaady thing works! Can't thank you guys enough for all the help you given me, learnt so much.

I'm testing it through a Marshall 2 x 12 8ohm cab so the speakers are fine. I'm definitely not getting 8/9watts out of it at the moment, although i dont think its far off to be honest. I'll change that gate resistor tonight and will then do some proper testing.

How would i use an audio probe? Sorry i've not used one before.

Well guys just to give you an update, the amp is now built..........................and it works! Mostly. I couldn't turn it on for very long as it was half 11 at night when I finally finished it, but I did have it on long enough to find that at full volume it wasn't quite as loud as it should be.

Now I just realised that the 1M Resistor on the Gate of the JFET is actually a 220K at the moment, I know this probably isn't the cause but I guess it doesn't help either. Also I have left out the tone control as well as I'm not too bothered about having one at the moment, may add one later, so that should surely help give a bit more volume as tone controls tend to lower the gain of the circuit. I have also got the PSU still set to 24 volts, so I'll try raising this to 28 volts tomorrow night as the TDA2030 datasheet specifies 28volts (14+/-) for 8/9 watts.

Once the volume is sorted I may try to add a bit more overdrive as it didn't sound like it had much, but one step at a time. I'm just thrilled that it worked first time, as you all know most circuits tend not to work at first due to things being missed!

Would it make a big difference if I used a 220uF Cap on the Output instead of 1000uF?

This is very true. I want to get this amp just right so i can use it at practice if my other amp dies or even at small gigs or even recordings.

Ah right yer I see. Thanks guys I'll order the parts now and will hopefully start building next week

Why is that?