Almighty TT hum --- help

It seems I may have misrepresented what is going on here. My cdp and tuner work perfectly with this old NAD and have since I bought it. I actually connected the TT to the tuner and aux sources and the hum was still there (got to be the TT, right?). I still have not investigated the possibility of damaged phono input jacks, but the hum just reeks of a grounding problem to me, but I can't see any problem. I'd love to borrow someone else's TT, but I don't know anyone who has one (sad, isn't it?). That way I would be sure to know which was the culprit that was causing this hum.

The plot thickens; sorry I misunderstood what you meant :^)

Let's assume the hum is the sound of 60Hz house current. Connect the TT to the phono input on the NAD then unplug the TT from the wall. Without its power source I doubt the TT can induce the hum. Remove the TT from its base and look at its wiring. Check its routing to see how free it is in its travel. Any chaffed insulation? Be careful; the cartridge leads are very fine and easily damaged. Are the RCA interconnects hard wired to the TT? Check their interface with the cartridge leads. If you can replace the RCA interconnects, try another set. Does your TT mute the output before it shuts off? Check the switch that mechanically opens and closes to perform this function. Is the headshell built into the tonearm? Is it removable? Clean that interface to remove tarnish and corrosion.

The weird thing about TT's is that the signal connections are allowed to float free of chassis ground. So the grounding that usually occurs through the RCA interconnects with other components requires a separate ground wire with a TT. Grounding the amp with your hand suggests your TT ground is not getting through. This separate wire which routinely takes alot of abuse from connection and disconnection weakens at the preamp end. Mine has been hanging by a single filament at least twice in its lifetime. Cut off about a half inch or more and reterminate it with a little spade.

When mounting the TT in its base take care that the RCA interconnects run away (instead of under) the motor and its power supply. Likewise route the power cord away from the RCA interconnects. If they must cross do it at a right angle. Experiment with the routing of the ground wire under the TT. Cut more holes in the TT base to separate the power cord from the RCA interconnects.

Once I loaded the TT into its base and the motor sat right atop the power cord pinching it to the floor of the base. That made the whole equipment rack vibrate! Keep trying, you'll get it.

Rockvirgo,

Thanks so much for the detailed plan of attack. I shall go forth, put the plan into action and report back!