What drives the sc-99 and other pro heads?

[Self-lather]

Clearly the sc-99 and other pro heads aren't using tweeters like I've always used to build diy stereo heads. What are pro heads driven by?

-Thomas

[opcode66]

Custom wound drive coils. Rolled and varnished onto a coilform. Built into the cutterhead. Sitting next to or within a strong magnet. Attached to a piston that moves the torque tube. Referred to as a transducer.

So, essentially the components of a speaker. Minus the diaphram. Bulit to translate ac voltage into back and forth movement. There is also some sort of "spring" mechanism that the piston is attached to. But, that's it.

There are also typically feedback coils as well. These have ac voltages induced within them. Mic level millivolts. They tell the special cutting amps how much the pistons are actually moving. The amp can use this feedback data to reduce resonance to near zero for flat frequency response.

[Self-lather]

Hey Opcode,

Thanks for all the detailed info. I've done a couple rounds of building stereo heads out of plexi, hot glue, wooden dowels, and tweeters, but I'm looking to take my next effort to the next level.

Has anyone here ever built their own drive coils?

[opcode66]

Plenty of people have. Yes. Some more complicated than others.

Flo makes a modern cutterhead himself.

http://vinylike.de/index.php/caruso/

Here is a video of one of the drive coils being tested.

http://vimeo.com/24224424

Here you can see his drive coils