Need A Cut on VMS80 for Wide Pitch Cut

[dave slagle]

I have a unique situation where I need a 3 minute track cut at a constant pitch across the entire playable record surface. I realize that a big feature of the VMS80 is to get more info in less space to avoid inner groove distortion but I need the opposite. I am not wed to the VMS80, that just happens to be the lathe that was initially used. I'll be happy to pay current market rate if anyone can point me to a solution.

dave

[flozki]

i dont think that i am in train trip distance to help
where are you located?

those VMS80 are technically all end of life. this is just the beginning...
40 years is already quite long operation time. for such a TTL graveyard.
so expect a little more attention ,maintenance in future.


send me a mail.
flo (aet) floka (doet) com

[dave slagle]

I do not own a lathe and have never used one. My previous attempts at this were done on the VMS80 and we seem to have hit the limitations which is how I ended up here. Ideally I want a track cut with a constant pitch of say 1mm per revolution or better yet a pitch that starts at 2mm per revolution and gradually decreases over a 3 minute play time to 0.5mm per revolution. This is all to make some measurements on tracking ability of a cartridge I am designing. Right now @ 33rpm the shortest track I have gotten to cover is 10 minutes long and I need to get that time down to 2-3 minutes.

dave

[flozki]

Ah sorry mixed it up a little with the other VMS80 thread. was not very clear

But that’s totally easy to do to spread up.
If you want defined pitch increase also easy. Just a little time to implement
On a lacquer master for pressing or is a cut on PETG enough? as it is more about tracking then that might be ok.
Also the Flokason Test record. same as ortofon Test record will help ..
It was made for ortofon internal cartridge test..around 2010
if you can track the two last bands I guess your cartridge will be excellent.i have seen so far only a few which manage last band without distortion

[dave slagle]

At this point I just need someone who can cut this track. I came across this link which is about a pitch control to increase effective space usage. This tells me that there are more modern lathes out there that would make this simple. I essentially need just the opposite of this which is counter to everything people traditionally do. Instead of getting the bulk of the recording at the outer track I need it weighted to the center. I can work with a constant pitch but as I said above starting with an aggressive pitch and ending at a finer pitch would be ideal. Communicating this need has had one place explain to me that this is a bad idea and the other said they can cut it only to get to actually trying to cut it and hitting a roadblock making 10 miunutes the shortest track they can give me. It seems that the VMS-80 can be 'tricked' into this but adjusting the settings required is too much to ask for that lathe in a working professional environment. As I said above I am not wed to any particular lathe and am just looking for someone who can help me solve my problem. My very first attempt at this was with lathe cut polycabonate. The pitch was not a problem but the quality of the cut was. Ultimately I will need to get records pressed.

dave

[dubcutter89]

Hi Dave!

Interesting project - if I'm allowed to ask, what is the purpose?
You said that you want to test "tracking ability" but I don't get how this record would tell you something about it.
At 1mm pitch per revolution (which takes 1,8 seconds @ 33 1/3 rpm) the groove velocity (and accelaration related to this velocity) is super small compared to any low volume sound (velocity = 1mm/1.8sec = 0,0005cm/s). That's 60dB below reference level and barely measurable with any dynamic system (MM or MC) especially if just going from outside-in and not alternating like sine wave...
I geuss the only performance test you could make with this kind of record is how well a tonearm is following the coarse pitch.
But then I think it is also more challanging to make a tonearm follow fine pitch precisely, because normal bearings are poor performer at low speeds due to slip/stick action etc...
For regular tracking test a low frequency tone (around 300Hz) is used with increasing amplitude to check how long the pickup is tracking properly (low distortion) and when it starts to skip.

Regarding cutting a record like this (without questioning why) - Most lathes can do spirals/time marks/ etc. which are normally used at the beginning of a record for the lead-in section or as track marks between songs. These are normally around 1mm pitch (or 25 LPI for imperial people). Nothing special, just wasting space to give shaky hands some space to drop the needle or as visual seperator...
For a more controlled way (let's say decreasing pitch in 100µm steps from 1000µm to 100µm) some tweaking is needed, but still doable.

Feel free to tell us more about your project and needs or contact via pm.
Lukas

[dave slagle]

Oddly enough, I am actually bound by a NDA on this one so I can't get too deep into it on a public forum. I was presented with a project and this particular test is part of that project. Rather than make endless calls and waste a lot of peoples time with this quirky problem I figured you guys here would be the ones in the know. With the last cuts on the particular VMS-80 the tech said that the lead in was limited to around 4 seconds and then reverted to "normal pitch" The leadout pitch was much more aggressive so in order to get the 3 minute there was 3 seconds of 1mm 37 seconds of say 3mm and then 3 minutes of around 0.3mm. I have made this work for my basic tests but the ~3mm leadout pitch is too aggressive and the transitions are problematic. The 1mm lead-in pitch would work and get me to the next step but the tech said he could not easily do that pitch the entire side. Ideally I would like to be able to specify a variable pitch but for the next cut a fixed pitch of 1mm would suffice.

dave

[dubcutter89]

Oddly enough, I am actually bound by a NDA on this one so I can't get too deep into it on a public forum.

That sounds bad!
Sad that the public has to be asked for advise, but the real information stays secret...

Ideally I would like to be able to specify a variable pitch but for the next cut a fixed pitch of 1mm would suffice.

Doable.
I could make it, but have to do some mods.
Not on a VMS80 but as you figured out probably that's not the weapon of choice for this job...
Contact if serious interested.

Lukas

[dave slagle]

I am by no means wed to any particular lathe and at this point I just need to find someone who can cut a roughly 3 minute file with a 1mm constant pitch. Any pointers greatly appreciated.

dave