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 in a long time, finishing it off with a really nice logarithmic volume control (Japanese made potentiometer).

Back to basics

With the 'easy' bit done it was time to dust off some metal working tools and buy some aluminium supplies from our local hardware giant (Bunnings). I started as best as I knew how and crafted our v1 cutter head first, knowing that regardless of any mechanical efforts elsewhere on the lathe, no cutter head = no lathe.

It was about a week in before I received the drivers and was able to energise what I had so far. It seemed quite promising, with physical vibrations of the torque tube detectable by lightly placing a finger on top while playing audio via a power amplifier.

Another week or so and we received our sapphire embossing needle from the USA! This was it, with this stylus, I could now place it on the cutter head and 'emboss' (not cut at this stage) onto Polycarbonate. I had a crude carriage and gantry knocked up by then with control software via the 3D printer's original mainboard, and I was ready to give it go. No joke, every CDRom in the house got embossed, as the material is compatible. We ended up getting some polycarbonate blanks made locally by a fabrication house using the CNC method and a good friend of mine from the local techspace helped me out with a few more that he cut up at home with his home made CNC! It felt great to have and hold some true 12" blank discs, they were all clear as any other colours are not easy to find in the material thickness that we needed.

Emboss, emboss, emboss!

Weeks and then months went by and we got better at 'making a record', with every attempt giving more data to analyse for another attempt, the so called rinse and repeat cycle. We could get an audible sound and it could 'sometimes' play, but honestly, it was hard work trying to get an embossed polycarbonate record to track well on a turntable.

Then amplifier issues cropped up, with the current amplifier simply not powerful (or clean) enough to yield appreciable sonic results! By this time though, since I had 'something', social media came to the rescue as one of my post got around the local music scene and then a (very accomplished, top 1%) Gold Coast based mastering engineer, Paul Blakey Mastering Engineer 12th & Vine Post, got wind of the project and asked for a meet up. I was ready to meet and discuss and had some 'samples' on my phone but nothing that I considered substantial. Nonetheless the meeting went well and we agreed to meet again and our place, and take a closer look at the lathe together. This subsequent meet up led to a loaner amplifier, as it was obvious that my current rig was not up for the demand. 

V1 prototype verdict?

Well... it played... kinda... and it sounded like the music recorded... kinda...

The biggest issues with my efforts using this method were multiple:

Researching further into the available lathe-cut record market, I could see some operators successfully selling polycarbonate, embossed records however I didn't want to include a list of disclaimers with the product and specific instructions on how to playback the record.

I wanted to cut records that anyone with a standard domestic record player could play. The journey must continue... 

Decision to make v2

The electronics, VU meter and DSP side was well underway, but was being let down by the crude mechanics and inaccuracies of the hand-built prototype. I sought after a CNC solution, as I just assumed that if the 1st prototype was make out of aluminium, that the 2nd could be similar with more accurate CNC designs and cuts. With this in mind I sought a CNC and found a 3-in-1 solution in Facebook Marketplace. This was a 'little thing' with a max build volume of 15cm cubed but I was making small precision parts that as a whole gain size and weight so I snagged it up and brought it home.

On opening, I found a 3D printer and CNC tool head still in it's original box and the laser head on the machine itself. As the laser glasses were missing, and I hadn't got around to making any CNC designs yet, I decided to test the machine by placing the 3D printer head on it and downloading something from the thingiverse. The supplied few grams of filament would be enough for a test. It was and frankly I've never looked back. PLA Silver is our material of choice, with the supplied snapmaker software handling the splicing and actual sending to the machine via wifi. It had been about a decade since my last attempts at 3D printing and things have sure changed for the better since then!

Version Two Prototype

Day by day I replaced more and more of the original lathe with 3D printed replacements. Knop's designs were essential to establish a base ground work for the elements required in the gantry and carriage set up. However as I opted for PLA instead of a fabricated (sintered?) metallic process (that would require a 3rd party to create), I needed to do quite a bit of rework to allow the PLA to have the structural rigidity demanded by the lathe.

Next I needed a real frame. Sourcing 40x40 VSlot proved difficult at best and our local Techspace (https://gctechspace.org/) had some lesson known and used 30x30 VSlot rails handy so I thought why not, I can just adapt to that. Well... I did, however parts and accessories for the other more popular form factors are much more readily available such as 20x20 (and are recommended if you pursue this insanely lengthy rabbit hole project for yourself).

Project gets serious

It was coming together and also time to order some actual black blank discs and a diamond stylus. This was procured by an overseas supplier. The shipment arrived and again the project's entirely dawned on me. With nothing more than these two key ingredients, blank discs and a diamond cutting stylus smaller than a safety pin, I had to fill in the rest and create a high-quality playable-on-any-turntable record.

Slowly but surely the 3D modelling and printing cycle continued and a mostly printed record lathe was now ready to test! By this time, we were up to cutter head v3 (see section below for cutter head evolution) and we were cutting black 12" records with a diamond stylus with impressive (but not perfect) results.

The general consensus from anyone that cared to listen to the audio samples believed it to sound 'pretty good', but all I could hear was the distinct sound of inter-modulated distortion, coming from a combination of the DSP peaking out in the high end and or the full-range drivers screaming at the level of top end they were being asked to handle. So, it had to be done and v4 cutter head was drafted, designed and printed.

Stereo cutter head evolution

Summary

After four attempts at making a stereo cutter head, we were satisfied with the results. In the end, it can't be disregarded that more power (from the drivers) = more weight and so the balance is quite delicate, with many other cutter heads seen in the wild opting for a more conservative driver size, to lower the total moving mass. This was a design choice of my own, and not necessarily the popular vote / choice for others.

What about some samples of the results?

The loaner professional grade Yamaha Amplifier from Paul was a god send, it instantly gave everything the high end boost and clarity overall that was needed. The cutting demands are quite high, especially in the high frequency domain with large differentials in levels in very transient signals.

We are proud of our results, and have a public google drive here with the latest WAV files:

https://drive.google.com/drive/folders/1eVCY1lRqWAWc5w2tE_EIQUHTmkwJI_zQ?usp=drive_link

Naturally, the newer files are considered to be of better quality than older files as the DSP is fine tuned.

Hardware Components

Mechanical System

Electronics

Audio Processing System

Software

Future Development

Build Materials

Links & Resources

Special thanks to Paul Blakey Mastering Engineer 12th & Vine Post for his learned advice and loaner amplifier:

https://www.12thandvinepost.com/