Moving magnet hum

Were you using a SUT with your MC cartridges going into the MM input on your phono stage? Likely you have a bad ground between your TT and your preamp, which is now loaded at 47k...not the much lower load seen by your SUT, which also acts to isolate your TT. This is a common problem when moving from low impedance to high impedance cartridges...your system is now revealing all your grounding issues.

Make sure your tone arm is grounded, and you have a ground wire running from the TT to your phono stage. If turning the TT motor on and off makes a diff, try lifting the ground on the motor or your phono preamp.

Oldears

Have you tried disconnecting your turntable ground wire? I had several MM's that I got hums with the ground wire connected but nothing when I disconnected the ground.

No grantees but whorth a try. Some of these cartridges are very tricky.

Good luck.

AEW

Thanks for the replies. I went ahead and removed the ground tab from the green (right ground) pin, and it solved the problem. It seems this tab was causing a ground loop with the well grounded tonearm. No SUT was used for the LOMCs as the Aleph ONO has plenty of gain. I dont think I have seen a MC with a ground tab, and it has been so long since I used a MM, I was not sure this was the problem. I had rewired my Alphason tonearm with shielded Cardas 4X33 awg litz. The sheild is grounded within the someam base and I still have a ground leads from the base to the TT chasis and to the phono preamp ground connection.
The ungrounded portion of the leads within the tonearm are sheilded by the grounded metal arm, and the leads are effectively acting as balanced (+ & -) even though I am using an rca connection. I used only 1M of cable with a total of 6 pf capacitance.

keep all electric motors away including a bedini clarifier

Same exact problem.  First MM cartridge and cannot tolerate the intermittent buzz. How do I know if this cartridge has a ground tab? Sumiko Amethyst. Thank you.  Lou

Most cartridges don’t have a “ground tab”. The 4 pins are used as hot and ground, respectively, in each of two channels in a SE connection.  But in a balanced connection to a balanced phono stage, the ground pins deliver the negative phase of the audio signal. So your grounding problem probably lies elsewhere unless one of those pins you’re using for audio ground in an SE connection is loose or disconnected. Check that but also look at the external ground connection between phono stage and TT or tonearm.

You fixed the problem! Is the headshell metal?

Some installations may require the cartridge shield to be elec�trically isolated from the"RG" terminal. This can be achieved by removal of the ground tab.

To the best of my knowledge, only a very few cartridges have one of the two "ground" pins connected to tonearm ground and hence to earth ground.  Decca and early Grado come to mind.  Certainly there may be others. So, Yogiboy, what "ground tab" are you talking about? I respect your fund of knowledge, but I am confused.  Sounds like the AT150MLX has a ground tab(?)

@lewm

The OP said his AT has a ground tab. All of the Shures that I have owned had a ground tab. Hence I quoted that from Shure. BTW, I have never seen a ground tab on any older Grados that I have owned!

By the same token, I have some older AT's that don't have a ground tab.  Back in the dinosaur era, I used to own Shure V15s... Don't recall any of them having a ground tab.  But we didn't have electricity yet back then, either.  So I may not have been able to see the tab by candle light.

@lewm 

You have electricity?

Yeah, we bought a hamster, and he's hard at work running on the wheel which drives a flashlight bulb.  Tesla told me about it.