[robinje]

Please be easy on me...  I'm electrically ignorant.   

I have an Ultra SL preamp which, of course, has a hard-wired 2-prong power cable.  How can the preamp be properly grounded without a third conductor plugged into the AC power outlet on the wall (yes, this is where my lack of knowledge comes into play).  Interestingly, I had a very low level (way below record surface noise) hum when using the integral phono section, even with the tonearm ground wire connected to the Ultra SL's grounding post.  It has never been at a high enough level to ever bother me during listening, and I only noticed it without a "needle in the groove" and when cranking the volume beyond normal listening levels.  But I decided to try something anyway...  I connected another ground wire back to my turntable (which also has a separate ground post) and the hum completely disappeared!  BTW - the turntable power supply has a 3-prong power cable.  Is it possible that my tonearm is now grounded through the turntable power supply back to the AC outlet instead of through the Ultra SL?  I have no idea why the hum went away, but whatever the mechanism...  it works!!!   

[Wayner]

I think you are confusing 2 different issues. First, the tonearm, which almost all are made of metal, can act as a gigantic antenna. Since the cartridge is a coil of wire sitting with the "antenna" tonearm and connected to a board that allows huge gain, very minute stray  magnetic fields can be amplified, many times and show up, along with your music as hum. This is the reason why we ground turntables.

The second issue involves "safety ground". If you look at your duplex outlet on the wall, there are 2 verticle slots and a "mouse hole" used as a ground. The widest vertical slot (the one on the left) is connected to neutral. If you go to your breaker box, you will notice that neutral and grouund are connected to the same terminal blocks.

Many appliances are supplied with only a two conductor cord. Your toaster, coffee maker and even TVs do not have grounded cords. The products fall under the home appliance catagory and it is assumed that the user will not operate this in extreme conditions, like making toast standing on wet concrete, hanging onto the metal case of the toaster.

Now even that situation may be safe, however, if the toaster developes a short, you may become the neutral conductor, while the toast is being made.

AVA equipment does not require a ground, just like these other appliances. The user should not use them outdoors in the rain standing in standing water listening to his/her stereo! Actually, the hot side of the incoming current goes into any AVA piece and directly to a fuse. Unless someone (unautohorized) fiddles around in the inside, the units are completely and totally safe.

In fact, adding a ground (to something that is not required) may induce noise to the system. In your case, the noise may have been from both sources, the tonearm and the tables power supply unit. In my case, with my 6 different tables, there is zero hum. I do not have an "extra" wire going from the ground lug of the EC preamp to the earth ground on the outlet (or water pipe).

Anyway, it sounds as tho you have cured the source of the hum or ground loop, and that's good.

Spin away.

Wayner

[Ericus Rex]

Could be your ground wire from the tonearm is damaged.

To expand on Wayner's excellent reply, you only need one piece in your entire system to have a three prong plug.  Since all the components are connected via interconnects, any unlikely catastrophic event in one would travel through the others and into the wall.  As Wayner said, having more than one could add noise, that's called a ground loop.

[robinje]

Thanks for your replies.  I understand this a bit better now.

[avahifi]

Thanks Wayne for the advice, better than I could have said it.

Frank

[turkey]

I think you are confusing 2 different issues. First, the tonearm, which almost all are made of metal, can act as a gigantic antenna. Since the cartridge is a coil of wire sitting with the "antenna" tonearm and connected to a board that allows huge gain, very minute stray  magnetic fields can be amplified, many times and show up, along with your music as hum. This is the reason why we ground turntables.

I thought this is the reason we thank the Deity that we now have CDs and don't have to rely on the funky old phonograph.