Blues Musicians From Mississippi

Hi guys, I am writing in the hope that someone out there can help a couple of electronics dummies resolve an electronics problem we have been up against for some months now. My young son Simon and me are Hobby Blues musicians and are particularly fond of the old Mississippi delta blues style. To get a more authentic delta sound, we have attempted to build a foot stomp board and have, with very basic knowledge, fitted a circuit with mike, battery, pre amp and jack. Please see photos and diagram attached. Upon switching it on, we were delighted to find that it worked fine; except for an irritating and permanent hum/buzzing when attached to the main amplifier or PA, which we do using a standard guitar lead. It is noteworthy that, when the main amp volume is increased the hum/buzzing becomes intolerable but the interference largely goes away when the jack is touched by hand. This has led many to claim that it is an earthing problem. However, we have no idea how to earth the circuit and what to earth it to when the board is made entirely out of wood. If there is any kind electronics wizard out there who can, on looking at our circuit, shed some light on what it is we are doing wrong or as to how we can resolve this problem then we would very much appreciate any advice given. Here are the images: A sketch of the circuit: A picture of the entire circuit: A picture of the circuit in close up: Many, many, many thanks Steve and Simon. Do you know what I found? Hi. It sounds as if you have inadvertedly created an earth loop. The circuit is okay, but I would concentrate on the layout. Double check that the earth connections are of a star configuration (i. E. Every earth on the board has to terminate on the same place i. E. Bolt, screw or wherever) ensure that the jack inputs and outputs are also earthed from this star point and that should cure the problem guys. In addition you may need to fit a substantial capacitor (220uF) across the DC input to the board again this should help matters. Also check that low level signals are not passing near any switching components i. E. Switch mode power supply, any logic circuits and data busses and finally check that any decoupling capacitors requried are present and correctly positioned in relation to their polarity. Feel free to contact me should you need any further assistance of if you still have any problems. Good luck Steve