Does this happen when no sources are connected to the preamp? If not, try an optical cable between your streamer and dac. I had a similar problem years ago that just couldn't be resolved until I did that. Very strange but it worked.
What would cause noise (ground noise?) when touching the volume control and tone controls?
I have a new preamp that I recently hooked up and I'm getting some interference or what may be ground noise but I only hear it when I'm physically touching the metal volume knob and tone controls. When I touch the metal top of the case in addition to the knobs, the noise will subside. Just looking for ideas to help isolate the cause. I think the case itself just isn't grounded sufficiently.
I have tried new power cables, RCA cables and plugging into different outlets with no change.