[dvw]

Polishing the contact will help. But I thought you have a hum when the cartridge/TT is not even connected.

Ground loop is caused by grounds that have different electrical voltage. This can cause hum. A bad connection will also cause hum (electrical contact, connector etc.) You can just touch the tip of the interconnect and get a hum.

There are 5 wires coming out of the TT. 2 signal wires and 2 signal ground, with a case ground. The signals and signal ground are in the "shielded" interconnect and the case ground should be connected to the equipment ground.

I don't think the JMT amp case is grounded. So if you use the ground pin and touch the equipment ground e.g. the negative contact of your DVD-A player. The hum goes away. That tells me your cartridge is working just fine. All you need to do is find a ground to connect the ground wire to.

But you also said, when the TT is NOT connected to the Lil'rat, you still got a hum. If that is coorect, then the problem is between the Lil'rat and the JMT and most likely is a coonector problem.

Now assuming you have no problem with JMT and another player. Then the problem is the Lil'rat. The connector could have for example a cold solder joint.

There is no good way of solving hum problem except by process of elimination. If the problem is the Lil'rat, getting new cartridge is not going to help.

BTW, if you are using AC power, make sure the wall wart is plugged in correctly. Plugging it in backward could cause ground loop (although I don't think that's the case since Lil'rat is battery powered).

 

[JML]

If the wall warts are not filtered, one or more of them could be the source of a 60 Hz hum. I had a similar problem with an AC transformer in a set of biamped computer speakers interacting with the transformers used for portables, causing a hum whenever I connected a PCDP or a tape player. A RS filtered & regulated adapter with the portable sources cured the problem.

 

[Matt]

...the contact cleaning thing and then stick batteries in the JMT and the Li'l Rat and see what happens. I'll report back ASAP.

Thanks for your continued help.

Best,
Matt

 

[Tuberoller]

This is a grounding problem.the table and the phono stage must be grounded seperately.Do not ground the table to an AC outlet either.since you have no grouned component to ground the table you may need a ground loop.This is a device which allows a ground to all connected components.It should be available at Radio Shack.That file cabinet is not a ground and when you ground to the outlet all the wiring in your house is acting as a big antenna.I promise you this is your problem.