Change on touch is not unusual, but if it actually works on touch, I would heavily suspect you are making an unconnected ground connection by doing so - especially since its both channels falling perfectly into place, and you measured all resistors going in (going by memero of what you wrote here).
Did you ever share pics of your build here?
Gustav
Hi Gustav, I tested your theory last October by checking extensively for any missing ground connections, but I wasn't able to find any. My XLR pin 1 has continuity with chassis.
Perhaps we could try and deduce the missing connection, if there is one, using the file I've attached. For both James and me, touching the top of the first BC107 in the GR control amp causes the comp to work normally at the lower ratios (instead of needle-burying into heavy compression regardless of input level).
The body of a BC107 has continuity with the collector, so we are touching the junction between the first and second BC107, the 1M and the 47K. The voltage here is supposed to be 15.1V, mine reads 14.9V. This voltage does not change when I touch with my finger - maybe a few millivolts, but that's all. I've marked the spot on the schemo with a red arrow.
My touchy finger has nearly infinite resistance to chassis ground, so I'm struggling to understand what the effect it is having on the the BC107. It can't be shorting it to ground. Perhaps the extremely high resistance of my touch is working in parallel with R73 (1M) and R74 (470K), which fall between the point I'm touching and ground. Adding my finger, assuming some high resistance, would have the effect of lowering the values of R73 and R74 would it not?
Ross