Cause of speaker static?

I completely agree with Rockvirgo. Digital components can be realy noisy. The biggest source is power line.
1. Try to use a good quality power cord
2. Try to connect your digital source onto the different power line or to the power conditioner/power plant.
The same tweaks I would suggest to do with your preamplifier.

Many good suggestions above... The likely noise source is the preamp itself. Tubes are indeed a possible suspect (if it's a tube pre). One thing I'd like to add is possible dirty/degraded switching contacts within the preamp. Suspect possible noisy / dirty contacts of a PC board edge-connector, input selector switch, tape-loop switch, tone-bypass switch, maybe even your interconnects (have you cleaned your connectors & cables with Kontact?). If you have to go inside the unit, first familiarize yourself with proper & safe servicing procedures, or take it to a Qualified service shop (not all shops are at the same competence level).

Thanks for all the responses. Amps are HK Cit 19 & Adcom 5400 and pre-amp is Yamaha CX-630. Detaching VCR from system does not alleviate problem. Static can be heard from 12' away but barely.