Cause of speaker static?

DAC's occasionally emit scary sounding, crackly static. Turn off the power amps, toggle the input switch on the DAC, turn the DAC off and on, restart the power amps.

If you've got a tube preamp...listen as you whap the preamp with the palm of your hand. This sometimes works with tubed guitar amps but it's not usually a permanent fix :-)

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.