interesting phenomena in the cutting room


We've (my friend Bob and myself) been working on an LP cutting lathe for some years. Its been a while refurbishing the lathe itself, finding parts and solving problems/puzzles, rebuilding the electronics, etc.

The lathe itself is a Scully, the cutterhead a Westerex 3D and the electronics the 1700 series built for the cutterhead by Westerex.

About 6 weeks ago we finally hit upon the magic combination of stylus temperature, vacuum, depth of cut, etc. It works beautifully! So we have been playing with parameters, including different amplifiers. The stock amplifiers were built about 1972 and are solid state.

Now those of you that know me know that I am all about tubes. But the stock amps worked quite well! As we gained familiarity with the system, we found out why: the Westerex cutting system is a high efficiency cutterhead- it does not take a lot of power to make the head work. It can easily cut grooves that no cartridge could ever keep up with, and do so without breaking a sweat. So the amps, which can make 125 watts, are loafing through the most difficult passages.

I had a Dyna ST-70 that I had rebuilt so for fun we swapped that amplifier in and it did quite well. Our next step is to use a set of our M-60s, as the cutterhead is an easy load relative to most loudspeakers.

What is interesting about this is that we can make cuts that literally demonstrate the audible differences between amplifiers, something that can be demonstrated on any playback system.

Its also apparent that the cutting process is relatively unlimited as a media compared to any other recording system. The dynamic range is well beyond that of analog tape or any digital system- like I said, it can cut grooves with such range that no cartridge could possibly keep up, yet is dead silent (if the lacquer is OK, that is). The real limitation in LP recording is the playback apparatus, not the cutters.

There is a fun little forum website for more information called 'Secrets of the Lathe Trolls'. Here's a post on that side made by my friend Bob (Bob has run a recording studio for some 20 years and was a roommate of mine in college):

http://lathetrolls.phpbbweb.com/viewtopic.php?p=19435&mforum=lathetrolls#19435
128x128atmasphere
Ralphmasphere,

Your comment
What is interesting about this is that we can make cuts that literally demonstrate the audible differences between amplifiers, something that can be demonstrated on any playback system.

Does not surprise me. I often wonder if the Music Matters Jazz and Classic Records Jazz releases don't owe some of their personality to exactly that.

I know the amps were not only different but vastly different power rating. I think both were tube in those cases, I would have to research to be more specific.

I'm betting the M60 will be awesome and your larger amps may be even better. I hope you do that kind of test and report back.
Ralph...

Is the plan to actually start pressing vinyl from this lathe or was it just for fun?

I agree with Albert, that with your amps, could be a killer cutting system. Will we ever get to hear anything from it???
Very cool. All makes a lot of sense.

Of course what value is there in arecord that can't be tracked?

Reminds me of the challenges i recall getting most vinyl players of the day to track the original telarc digital recordings without clearly audible mistracking and distortion. Those seemed to push the limits of what was practical back then but clearly it would be possible to do more at the expense of playback time.
Ralph - what cutting angle are you setting the machine to ? So we can get that pesky "RTA" set correctly :-)

All in good fun

Peter

PS For explanation of "RTA" see previous post about the USB Microscope