Grado Moving Iron Cartridges and Hmmm . . . [Archive] - Audio & Video Forums


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Ray H
12-29-2004, 11:32 AM
Apologies if this topic has been covered elsewhere. I really did attempt a search, but the search engine gagged on the word "hum" since it didn't meet the requisite four letter minimum... Anyway, for the gurus here, Grados are generally accepted for their tendency to pickup and transmit induced motor hum through the tonearm wiring and amplified for delivery as an added sonic bonus to the loudspeakers. The worst offenders typically center on TTs whose motors are onboard and unshielded - Rega and similarly designed TTs* equipped with syncronous AC motors and non-metal platters. My question is, would attempts at shielding the platter, itself, be of benefit? In my childlike innocence, it seems that applying high metallic content spray paint to the underside of the non-metal platter would result in a barrier against the low frequency emanations from the TT motor. Opinions, flames, other reactions, or all of the foregoing?

*No slight against these wonderfully thought-out but deceptively simple designs intended. I am a very pleased owner of a Rega's Planar 3/RB 300 combo equipped with an ancient Shure V15 Type V-MR cartridge and nary so much as a hint of buzz within immediate earshot of each of my VMPS Tower II's 12" bass drivers.

12-30-2004, 10:30 AM
Tried a Grado Red a while back and it hummed a little bit on my Rotel belt-drive with an aluminum platter. Wasn't terrible, but later switched to Shure (have an M97xE and a V15Vx). No more noise, much better sound (imho). You can't shield something just by putting metal around it. The metal has to be grounded.