Thanks blackcorvo for answering my questions. I'm tempted to try some of your suggestions.

I too have some things to add:
1- I've been mainly experimenting with drive channel and trying different diodes,I've made a topic over diystompboxes :
http://www.diystompboxes.com/smfforum/index.php?topic=114013.msg1057967#msg1057967
I've found out the most effective way to make drive channel better, without altering too many things is diode limiter (check above link). You can get a nice transition from crunch to distortion.

2- Another interesting thing I found out was this video:
https://www.youtube.com/watch?v=rRAv76ylAcI
what this guy did is he simply removed C12 2A274K!
I tried this,and it's AMAZING ! when you remove C12, amp will sound clearer and there is an increase in volume. I really suggest trying this and removing it or replacing it with something lower (like 2A272K).
I'd love to know the science behind it,if some one can explain?!

3- I changed my volume pot(B50K) with my bass pot(A50K),now volume is more versatile specially when in drive mode. It's a simple effective tweak. :dbtu:

Hi, sry for bumping this topic, but I have some questions regarding these mods, and if I wanted to post a new topic I had to reference to this topic more than once :loco

It's little confusing, does paralleling a 1M resistor to R7 has any effect or not ? (reducing gain when we are in overdrive channel)
Pot labeles on my amp are: B104 for gain,ALPHA B50Kohm for treble, A50Kohm for bass and ALPHA B50Kohm for volume. I think I need a log taper for volume,and since I can not find any log pots where I live, can I swap bass pot with volume pot ? (won't there be any problems with bass ? )
Should I use anti log pot for gain ? if so,how can I change a linear pot to anti log ?