Ground loop with Miyajima Premium mono

Thanks, Ralph. I had the suspicion that this was the case, but actually forgot to mention it in my post. But, hum is hum and must be eliminated when possible.
It would not surprise me to learn that the hum issue has much more to do with the circuit design of the particular phono stage than with the cartridge itself.

I have tested a Torlai mono cartridge with single coil too.
Mr. Roberto Torlai is a Italian cartridge maker.
Same hum from speakers and the same answer that has given Mikelavigne on as to resolve the problem.Mr. Lukaschek,Benz Micro chief,says that the problem is greater with low output mono
cartridges.Dynavector and Lyra monos has double coils to avoid
loop (this is written on respective websites).
Matter more intriguing for me.

Sorry to change the subject somewhat....but I've been considering purchasing a mono cartridge and am concerned as to whether or not playing it on a stereo recording will cause groove damage. Besides playing mono recordings, I sometimes switch to mono on my preamp to play stereo recordings from the mid-sixties that have that ping-pong extreme left-right separation as well as stereo 45s to remove (to a certain degree) extraneous noise.

Somaxx, I get that this is the explanation on two different sites. Despite that, its not correct.

A ground loop is formed when there is a gain stage that shares a ground with another gain stage, such that it can amplify the currents in the ground circuit.

A classic example might be if a preamp and an amplifier are both have their circuit grounds connected together with their respective chassis, both of which get their grounds from the ground prong of the AC outlet.

In this case, there is no such gain stage; IOW, the cartridge is a passive device. If there was a gain stage between the cartridge and the phono section, then it would be possible, without one you don't have the conditions for a ground loop.

I know ground loops can be mysterious, and recalcitrant hums can be frustrating, but they are not the same thing. I can think of other scenarios that are far more likely:

1) If there are 2 windings in the cartridge, one could be defective

2) A wiring error is occurring in the process of connecting the inputs of the preamp together.

3) the tone arm ground and the minus outputs of the cartridge have become confused

4) if the cartridge has a metal body (or employs for some unknown reason, a ground tab) and is grounded to the arm, you will get hum pickup as the arm is no longer able to shield the cartridge signal.

My Miyajima BE Mono should be arriving this week and I look forward to hearing what all the fuss is about. I'll be using mine on a Schick 12" arm.

Lula, I think I can answer your question. Some mono cartridges (such as the Miyajimas) are "true mono" designs that do not have vertical compliance. This type of cartridge will damage a stereo record. Some other mono cartridges DO have vertical compliance and those should be able to play a stereo record without damaging it. From what I have read, Grado monos are in the second group but there are probably others as well.