Summary

Wow what a journey this was, 14 months later I've called it and this project is deemed completed. I didn't initially set out to build my own lathe, rather I attempted to buy a commercially available, working lathe that I knew would need some audio processing magic to get some good cuts out of. The market for a record lathe turned out to be quite grim, with a single global supplier the only 'commercially available' option, huge lead times (stories of over 2 years is not uncommon) and other odd requests associated with obtaining one.

Looking at the (stereo capable) landscape in general, it seems that Neumann was the real pioneer back in the day, creating the still world class models: VMS-66, VMS-70 and VMS-80, each representing the decade 1960, 1970, 1980 of when first released. And then... nothing... no new models hit the market as the vinyl craze was over and other formats had essentially made it obsolete. Some were still running the American made Scully models, however the general consensus was that the cutter head was the make or break it point.

At this point I considered getting my hands on a 'needs work' lathe, to acquire most of the mechanical framework, and then perhaps build up from there. This proved difficult, as people's worth of non functional equipment seemed quite unrealistic. There is a current reverb post at time of post for a non-functional Neumann lathe for $100k Australian dollars. Crazy amounts for something that doesn't work if you ask me!

So then the realisation came that I might need to DIY more than 'just the cutter head' on an old previously functional lathe, I would have to go deeper and consider making the whole lot...

Initial research

This project seemed like a huge feat as more research into the area and a 8-10 year catch up on the lathetrolls forum (dedicated to vinyl record lathe discussions) lead me to believe that many have tried and just simply failed to produce good and or reproducible results cutting vinyl, including teams of people! (for example Westrex engineers, and more recently a (failed?) kickstarter effort by Phonocut) https://phonocut.com/

Phonocut's concept in principal was what my overall goal was from the get go - a fully automated solution just plug in an audio source, put a blank disc on and press record.

Acoustics, audio analysis and DSP are where I believe my true strengths to be, closely followed by programming and automation control (see my other projects). Surely I could give this a crack.

Reading the fantastic write up by @grooguy's post on the lathetrolls website encouraged me that real results were possible with a hand made build, coupled with some aggressive DSP. 

Version one prototype

Luckily, the project's inception coincided with my 3 weeks Christmas break over the 2023/2024 period. This gave me some solid time to give making a prototype. A friend gifted me a 3D printer with the main board and PSU and this gave me some mechanical and control base to build from. Honestly, at this point in the project I was quite mechanically lost, my strengths are in the DSP /electronics / software side and all the mechanical requirements of a working record lathe seemed quite daunting.

Electronics

All circuit designs were modelled using LTSpice on a mac. This gave me confidence that a subsequent prototype of these designs would function within the tolerances that were expected. Brown Burr based op amps are used for ultra low noise and high bandwidth properties. The audio processor has a variety of functions and all audio is routed via these dedicated preamp sections. A 5 stage, dual channel phono preamp provides the VU meter with a calibrated signal that is used as the playback metering. A balanced input provides the audio source and record metering. Further metering is provided for both peak level and peak limiting functions programmed on the 24bit DSP module. A balanced-to-the-ohm headphone amplifier provides the best monitoring I've heard...