Microphonic amp

[mlp-mx6]

Bob,

I'm just glad you found the source of the oscillation. +1 on the great clean tone. Chasing down hum is a challenge too. Believe it or not, at times I've solved a hum problem by doing the Fender-style scatter ground, undoing a "star ground" system. Seems that every layout has its own preference...

Michael

[Bob-I]

Bob,

I'm just glad you found the source of the oscillation. +1 on the great clean tone. Chasing down hum is a challenge too. Believe it or not, at times I've solved a hum problem by doing the Fender-style scatter ground, undoing a "star ground" system. Seems that every layout has its own preference...

Michael

If you look closley at the picture you'll see a brass rod under the pots. I'm grounding everything to this rod expect the power supply, which is grounded to the PT lugs. I'm not at all a fan of star grounding (even though my middle name is Starr)

I'm thinking that the hum is heaters. I'll rework that layout and see what the results are.

[BobW]

Bob-I Check out my Bassman layout, I use a preamp ground bus and tie all local ground returns close to each filter cap ground, then let the bus tie them all together. It really works, this insures each gain stage has it's own return path and all circulating currents in each gain stage stay within each stage. This helps reduce the crossing o fcurrent paths for each filter cap and provides for a quieter amp. Using this layout, I cannot hear a difference in noise when the amp is either in or out of the top shielded amp head.