humming issue, and grounding schemes...help..

[dai h.]

if you want to do some reading, here is an article which I have found useful for understanding some of the underlying theory (it also contains links to a bunch of other related articles) :

http://ampgarage.com/forum/viewtopic.php?p=1471#1471

[Shea]

Whenever I've had a ground-related problem that I just could not figure out, I always beat it by going old school: soldering the ground lugs on pots to the backs of their cases, or to a spot on a brass grounding plate right next to the pot. Although that's what all those star grounding/galactic grounding tutorials say you shouldn't do, it worked.

Shea

[dai h.]

I guess the idea that you shouldn't or can't put things through the chassis isn't really true (easy to see if you just look at some old Fenders or Marshalls or a Dr.Z which is a new amp that uses multiple grounds on the chassis). You just have to think about stuff such as for example in the above article, it says to keep the preamp grounds low resistance and one way of accomplishing that is to use a bus and keep the ground points close to ea. other, but another way could be to make the ground bigger from a line expanding out as a plane which also satisfies the requirement of keeping resistance between the points low (you get ground loops which is bad but many grounds loops become a ground plane which is good). You can do things all different ways except the wrong way I suppose. It definitely helps to at least have a little bit of theory rather than trying to guess at things.

[swt]

ok...i think i'll update this as a way of gratitude to all the people that contributed and tried to help me.
i've solved it. completely rebuilt it using HAD specs...that means, ground bus for pots, and pre ps caps, attached to ground near the input, and power amp and power amp supply attached at the other end of the chassis. seems that these kind of circuits work well this way!.
it's amazing how different circuits react to different types of grounding. my high gain, and marshall type of amps are amazingly quiet with a galactic grounding .
thanks again for the help!!