The Secret Society of Lathe Trolls

tape · Joined: 25 Jan 2007 Posts: 90

I found this video of a guy playing cd's:

http://www.youtube.com/watch?v=baz1PxRdJd0

It's hard to see how he has recorded them, does any of you have an idea how he has done it?

judgeing by he fidelity, it's not mechanical...

andybee · Joined: 14 Aug 2006 Posts: 63

i have recorderd some cds, can be cut with diamond on
any lathe. I used a selfmade construction to hold the disc
in center and place.
Razz

volo · Joined: 13 Jan 2007 Posts: 4

Hi andybee,

Are you planning on re-opening your website forums?

tape · Joined: 25 Jan 2007 Posts: 90

dEAR Andy, I dont doubt that it can be done:-)

My question is simply how to make the cutting needle vibrate with the music- Lets say I tried to cut on cd's using a standard turntable with another needle, is there then any way to connect an audio input to the turntable and make the needle vibrate?

thanks

cuttercollector · Joined: 11 Jun 2006 Posts: 285 Location: San Jose, CA

Uh... in theory if you drove a signal into a phono cartridge the needle Would vibrate, but there is a lot more to record cutting than that.
The main issues being something to guide the arm across the cutting surface in a slow uniform manor so you would get actual normally spaced record grooves. The other is that a normal phono cartridge and stylus are not shaped for and can't deliver enough energy to actually cut grooves. The two things are almost exact opposites. You need a small fragile low mass smooth stylus to play grooves without wrecking them and you need a big powerful rigid assembly with a chisel shaped stylus with considerably more weight to cut them. These cds were probably cut on some sort of normal record cutting lathe.
There were primitave home recorders that used the same arm and cartridge to cut and play grooves. Before that there were really primitive devices that did the same thing accoustically with no electrical tranceducers at all.
That is what the little modern kit gramaphone replica device does. It makes some sort of groove accoustically on cd media or the like.

tape · Joined: 25 Jan 2007 Posts: 90

Thank you very musc , that was very informative.

From what you are saying, do you think it would be possible to buy a pickup / cutterhead and mount it on a turntable like Technics 1210?

I only want to cut flexidiscs and the fidelity is not important....

cuttercollector · Joined: 11 Jun 2006 Posts: 285 Location: San Jose, CA

Hi, no ofense but from your responses there are parts of this you haven't quite grasped. It's OK you are learnig about a fun and forgotten art/science.
To sort of reply to two threads, here and about the toy kit recorder, the person with the Garard turntable with the crystal cartridge plugged backwards into an amp of some kind just drove the cartridge backwards as a cutter from some speaker output or line output. Any transducer (well most) will work either way. You could hear a tiny sound from a microphone if you hooked it up as a speaker or you could use a headphone as a microphone (did that), so a heavy tracking crystal cartridge will vibrate if you feed signal in. The deal is he was using a record with pre-existing grooves that were quiet and unmodulated. The cartridge just put little modulations into them. I did the very same thing with some of my old 45 singles with a wind up gramophone. some of them still have me shouting hello hello into the place where the sound came out etched in their leadout grooves.
But to actually cut precise grooves requires a lathe, something to guide the arm to make the grooves. My next kid experiment was to take the same gramaphone, I found an old blank home recording disc, with no grooves, hooked a speaker to an amp, placed it over where the sound would come out, played music through the speaker and attempted to guide the arm acroos the disc by hand. It sort of worked but I only got a few playable grooves per side because my hand did not make a very good feed mechanism and the grooves were erratic, widely spaced and not too deep but they did play.
So, to actually cut a blank ungrooved disc, not to be redudndant, requires a heavy large cutting head driven by an amp of adequate power, in an arm or lathe assembly which is moved across the disc with some precision by a mechanism, to produce finely spaced uniform grooves, with a stylus that will actually CUT the groove (producing a thread or chip), and the motor must be strong enough to keep the turntable rotating at a constant speed during this process which produces much more drag than just playing a record.
There have been all sort of things tried historically including pre-grooved blank discs and just driving a primitive pickup cartridge backwards off the amp's output, simple units thad did the same thing but had a feed screw mechanism you could engage to drive the arm as a cutter, like the Wilcox Gay Recordette JR. models, to biger pivoted arm cutters with a dedicated cutting head like the Presto picture you found. BTW that particular one was my old unit that the Presto history guy got from me. He is quite knowledgable and a real nice guy.
Then the next class of cutters start to use actual ovehead linear lathes to move the cutter across the disc, which is how all the biggest pro gear works.