MC demagnetizer, how many use one, any concerns?

Cpdunn, if you are concerned with momentary loss of performance in order to reach a goal of excellent performance after a short break in period, I suggest you not clean interconnects, speaker wires or ever shut down any of your gear.

There is no free ride with this, same as the rest of life in general. I don't see what the problem is. Do a little work, suffer with slightly poorer sound for a very short while, reward is significantly better sound for the next few months. What's to think about?

Lugnut, you might look for something used. Mine was built by Kisiki and is labeled Audioquest. It is at least 14 years old and still going strong. Another (used) demag would be the Sumiko FluxBuster. I used one long ago and remember being pleased with it as well.

Among new, current production units are: Aesthetix, Audio Physic, Gryphon and Benz. Perhaps Audiogon members can list others I am unaware of.

Demagnetization is not a new idea. Today it is considered important enough to phono performance that it is being employed into the original circuitry of the new Aesthetix and Boulder phono preamps.

I use a Kisiki de mag on my Koetsu Rosewood, just as I did with my (previous) Benz Ruby 2.

Moving coil cartridges do not require treatment as frequently as moving magnet designs. No more than 20 seconds of de magnetism every two to three months is sufficient.

As to requiring demagnetizing more frequently after having done it once?

There is a change in the tonal balance, dynamics and staging of a Benz and Koetsu immediately after demagnetizing. This is followed by several days of waiting for the cartridge to break in or "settle" to best sound again.

Perhaps your friend does not like waiting through this interim period and prefers the sound of his cartridge having been recently de magnetized. This may prompt him to continually repeat the process.

When I had a Benz Ruby 2, there was a time when I got caught up in the frequent demagnetizing. The high frequencies are soft and diffuse immediately after treatment and as with all settling in periods, the sound immediately after that is not as comfortable. Waiting a bit longer will net you sound as it was when new and fully broken in.