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Re: I appreciate your sense of humor..............

Posted by Charles Hansen (M) on May 3, 2007 at 08:41:14

In Reply to: I appreciate your sense of humor.............. posted by mothman on May 3, 2007 at 01:15:39:

<< I have a VPI table with rca junction box >>

But what cables are you using? I doubt that eliminating the RCA plugs will solve the problem you are experiencing. I would guess that instead the cable itself is *not* a "twinaxial" design (two conductors symmetrically arranged inside a shield, which is *required* for balanced operation. If the cables are instead "coaxial" (a single conductor inside the shield), you will never get rid of the hum when running balanced.

Here is the ideal connection:

a) There are four floating connections on a moving-coil cartridge. These form the "hot" and "cold" inputs for a balanced connection.

b) The tonearm tube is generally made of metal and provides shielding for the tonearm wires inside. There is almost always an external connection available for this (usually some kind of binding post). This should be brought to the grounding post on the back of the preamp with a single wire (to avoid ground loops).

This is trivially done by using the Ayre phono cable and a tone arm that has a DIN connector. When there is an RCA junction box you will need to use the proper phono cables (as shown in the schematics) plus a separate ground wire from the ground terminal on the junction box to the ground terminal on the preamp.

I strongly suspect that your RCA - XLR cables aren't constructed properly. Why don't you see if you can borrow a set of the Ayre cables (and use the separate ground wire) before you start hacking up the junction box?

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