Zu 103R + Thorens 124 = Hum

I recently purchased a Zu 103R, it is a Denon 103R which is nuded and fit into their own aluminum body, along with other refinements. I installed it on my arm last night and before I dropped the needle to the record on my Thorens 124, I first turned up the volume on the preamp to test for hum, noise, etc... It was quiet as could be at noon on the volume setting and a swipe of the stylus with the brush told me signal was passing just fine.

Once I lowered the cartridge to the record, however, a horrible hum started sounding through the speakers. It wasn't hum akin to a poor ground, there was no static, no buzzing, a definite steady, very low frequency hum. This hum very quickly began to rise in volume (without me touching anything) until I leapt across the room to turn the volume to zero and lift the needle from the disc.

I have read that the iron platters on these tables can have magnetism problems associated with them, yet I also know many people use the DL103 with this model Thorens with no issue. I can't imagine the cause is the aluminum body employed with the Zu design seeing as it is diamagnetic.

Any thoughts? Thank you for any help you can provide.
The type of hum that you've experienced isn't caused by any electromagnetic interference and is commonly referred to as acoustic feedback. This can easily be identified by an increase and 'swell' in the hum until you lower the volume control setting. It's caused by the sound pressure level in your room being fed back through the wall or floor and the table/arm/cartridge interface exciting its specific resonant frequency which then continues to build upon itself. That resonant frequency is affected by the compliance of the cartridge, so using one cartridge can result in acoustic feedback while another may not in the same room and table/arm setup. It can also be affected by the platform that the table is setup on but it can be a difficult problem to resolve. You might try to relocate your table position in the room or to isolate the table to see if you can avoid the problem, but in many cases the only solution is to find a different combination of table, arm and cartridge that doesn't exhibit the problem in your listening environment. The resonant frequency is also affected by the mass of your tonearm/cartridge combination, so you might try to add some mass to the headshell of the arm (and then of course rebalance it accordingly) to see if that might shift the resonance to a more benign frequency that would work in your room. I wish that I had a quick and easy solution to your problem but exceptional analog replay can be difficult to achieve, however once experienced it's well worth the trouble. I wish you the best of luck in resolving this issue and please let us know if you find a solution.

A similar problem posted. I also found sometimes the untighted RCA cables also cause the hum.

08-20-08: Azmoon
Problem solved! Disconnected the 4 cart tags. One of them was not very tight so I took M. Fremer's tip and placed a toothpick in the tag and squeezed it with needle nose pliers. This tightened the connection. Hooked it all back up and the hum is gone. Thanks for your help on this irritating problem.
Azmoon (Threads | Answers)