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In Reply to: Tube amps and DVD not a good mix? posted by Paul K on January 16, 2001 at 07:00:15:
It's the 60hz power line beating against the 59.94hz vertical video rate. Watch it, it takes six seconds to climb up the screen, the difference between the two frequencies. Enough science! Two possible causes:1) Your tube amp may have a defective power transformer with significant leakage to ground. In that case it's a shock hazard and should be checked by a service shop. Ask them to verify both sides of the AC line are isolated from the chassis. You can do this yourself with an ohm meter. UNPLUG THE AMP! Readings should be at least 1 megohm from either blade of the AC cord to the chassis or an RCA connector shell. If it has a three prong cord, the center round prong should show close to zero ohms to the chassis.
2) You have a ground loop. Ground loops come from hell! What this means is that somewhere in your system there is a path to the house electrical ground in two or more places. Cable TV is one commen place as this is bonded to the electrical system at the main house panel. A TV or Satellite antenna is also grounded for lightning protection. Is your computer tied into the system in any way? Sound card? If any of your components have a three wire AC cord, this makes a ground loop back through the electrical system. I would suggest professional help with this. Never disconnect the CATV or an antenna ground from your house ground rod. Doing so could destroy equipment and start a fire in the case of a lightning strike. Using "ground lifters" or commenly known as 3 prong adapters with the ground wire cut off may work on three wire power cords to stup the video hum. But this may also cause a safety hazard in some cases.
There is no reason a tube amp should have this problem over a solid state amp.
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Follow Ups
- Re: Tube amps and DVD not a good mix? - Glimmie 18:44:07 01/16/01 (0)
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