I recall this topic as being controversial years ago, some saying that it is a problem, some saying it isn't. IIRC, it was proposed that a charge would build up around the pole pieces and the coils, or something like that, and gradually make the sound a little cloudy. I have a cartridge demagnetizer that was sold by Audioquest. I try it occasionally, but I've never heard a difference before and after in the 25 years I've owned it, even after 1000+ hours use on a cartridge.
But please note this: demagnetizers of that sort were only recommended for use on Moving Coil cartridges - they should not be used on Moving Magnet or Moving Iron models.
Now, what the story is with that test disc demag, I dunno. Might be a different principal that is harmless. I never heard that there was a similar effect on other than MC types.
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Steven Smolian
Sent: Monday, June 06, 2016 11:06 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] Cartridge demagnetization
At least one source of cartridge magnetization is static electricity. I use a Zerostat to discharge static from records and the same device aimed at the cartridge. I've no idea how to measure theresults but suggest the process a part of your "good housekeeping" routine. That inexpensvic elittle device can really make a difference.
It just occurred to me to wonder how it affects tapes, particularly in fast-forward and reverse which is where static electricity is most intensively generated. ? Might the discharge cause noises on the tape? Gotta try it.
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Melissa Widzinski
Sent: Monday, June 06, 2016 10:52 AM
To: [log in to unmask]
Subject: [ARSCLIST] Cartridge demagnetization
I'm curious about the idea of cartridge demagnetization for turntable cartridges. On the Analogue Productions "Ultimate Test LP" there are lateral and vertical pink noise tracks that one should play "5-10 times after every 300 hours of normal LP playback." I'm having trouble finding any credible information on this topic by searching online - just finding opinions and the usual forum chatter.
Does the cartridge actually become magnetized during playback? I understand that there already is a magnet in the cartridge, but is using the cartridge to play back discs causing a harmful increase in magnetization or magnetizing other parts of the assembly?
If the cartridge is gaining magnetization, does changing out styli on a routine basis reduce that magnetization? Does playing pink noise from the test LP actually demagnetize the cartridge?
I should really have done some test transfers before and after running the pink noise tracks 5 times, but alas, I did not. The anecdotal comments on cartridge demag are that high frequency response is improved after demagnetizing. Does anyone have recorded examples of this, or commentary or reference material on the matter?
Audio Preservation Engineer
Media Digitization and Preservation Initiative Indiana University