Tokyo Dawn Records SimuLathe

The Cut version’s default view.

This clever new plug‑in can be used by vinyl cutting engineers to help get the best results from their tools and medium — or simply as a way to learn more about vinyl mastering.

I find it remarkable to be writing this, but vinyl sales have grown consistently over the last 15 years from their lowest point in history in 2006, and are currently at their highest levels since 1990! Vinyl sales have even surpassed CDs after a 35‑year reign, partly as casual music listeners have switched from CDs to streaming services and partly because keener music lovers are (re)embracing the physicality and involvement of playing vinyl discs. As a result artists, both famous and hobbyist, are releasing more of their music on vinyl, and sometimes exclusively on vinyl, and the demand for mastering houses able to cut vinyl masters is on the rise.

However, mastering for vinyl is a fiendishly complicated business, with a large number of interacting parameters that all have to be carefully juggled and optimised to squeeze the music onto the disc’s surface in the most sympathetic and reliably playable way. In the past, the mysterious black arts involved in skilful vinyl mastering took many years of apprenticeship and bitter experience to acquire, with many unusable lacquers and damaged cutter heads along the way. But Tokyo Dawn may have found a way of making that process somewhat easier for professional mastering engineers — while also allowing the curious amongst us to explore the weird and wacky world of vinyl mastering for ourselves, at least in a virtual sense, without having to install an eye‑wateringly expensive (and increasingly rare) mastering lathe and all the associated hardware.

Overview

TDR’s SimuLathe is a DAW plug‑in available for Mac OS 10.9 and above or Windows 7 and above (both for 64‑bit platforms only), and available in VST2, VST3, AAX and (for the Mac OS) AU plug‑in formats. In addition to the demo, there are two different versions, called Ref and Cut. The less expensive Ref version is intended primarily for educational and referencing purposes and provides a complete simulation of the entire disc mastering process, based on one of four representative lathe emulations, with all of the real‑world parameter options. It even goes as far as replicating how a cut disc sound will sound when replayed, using one of three carefully modelled pickup cartridges (complete with dust and damage artefacts!).

For anyone interested in finding out how their track(s) could sit (and sound) on a vinyl record — be it a single, EP or a full album — SimuLathe Ref affords the opportunity to explore a wide range of options and to make decisions in advance over settings for the classic elliptical filtering, recorded level on disc, groove excursion, widths and velocities, overall playing time, and much more besides. Incredibly, the virtual cut groove can also be explored in remarkable 3D detail through a virtual microscope, and any problematic or risky areas are automatically highlighted by the software.

A virtual microscope allows you to check the 3D cut groove in very fine detail!

The more expensive Cut version is aimed at professional mastering studios with one or more real vinyl cutting lathes. The SimuLathe software allows professionals to check and adjust the audio material, and assess the optimal cutter settings in advance of lowering a real cutter head onto the lacquer. The user interface looks much the same as the Ref edition at first glance, but it actually includes many more advanced features, including special limiter functions to control directly the groove excursion, width and velocity.

Audio filtering parameters are considerably more comprehensive than the Ref version, too, and there are calibration options to ensure specific real‑world disc lathes can be replicated precisely with the benefit that disc authoring can be fine‑tuned in the virtual world before cutting the lacquer, thereby avoiding any nasty surprises. Even the specific pitch computers used in popular hardware lathes are emulated precisely, including those employed on Neumann’s VMS66 and VMS80 lathes, amongst several others. As a result, disc surface space utilisation, groove excursion, groove widths and land areas, velocity hotspots, and audio quality can all be thoroughly analysed and optimised long before the cutter head is even warmed up!

...mastering for vinyl is a fiendishly complicated business, with a large number of interacting parameters that all have to be carefully juggled and optimised to squeeze the music onto the disc’s surface in the most sympathetic and reliably playable way.

Disc Basics

The world of vinyl disc mastering is very technical and highly specialised, of course, and so has a terminology all of its own. So for anyone without experience of the field some background reading and/or watching of videos is going to be essential before understanding and operating SimuLathe. The Tokyo Dawn user manuals are extremely good at explaining the concepts, terminologies and technologies, though, and the company have produced several excellent videos explaining what the SimuLathe software can do and how it does it, too. There are also many third‑party books and videos explaining the intricacies of vinyl mastering, of course, for those with a serious passion for the topic.

I don’t have the space here (or the detailed knowledge, really) to write a treatise on vinyl mastering sufficient to explain all the details, functions and parameters of the SimuLathe software, but I can give an overview of the main processes and facilities.

The first thing to know is that vinyl lathes operate in a kind of Mid‑Sides format. Mid information moves the cutter from side to side, so affects the width and excursion of the groove. Sides information alters the depth of the cut in the vertical axis. The combination effectively deposits the left channel audio on the inner side of the groove wall (closest to the centre spindle) and the right channel audio on the outer side of the groove wall (closest to the edge of the disc).

Needless to say, the vertical excursion has to be managed to ensure it never reduces to zero, leaving the replay stylus with nowhere to go, and the lateral excursion has to be managed to make sure that one groove doesn’t impinge on the adjacent grooves in the previous or following revolutions. Both errors would lead to skipping and unplayable discs!

The default cut configuration and lathe calibration options in the Cut version.

Related to the latter point is that the cutter head not only wobbles according to the audio signal, but is moved progressively across the disc surface by the pitch system to create a spiral track working from the outside edge to the inside of the disc. Early vinyl records (before the mid‑1960s) generally used a fixed spiral pitch, designed to be wide enough that successive grooves could never impinge on each other. This guarantees a playable disc, but is relatively wasteful of surface area and so modern discs use a variable pitch system which varies the spiral pitch according to the audio signal.

This arrangement allows much more efficient use of the surface area, meaning longer and/or louder tracks can be cut, and it does it by anticipating when loud sections are coming so it can increase the groove pitch to create sufficient space. Quieter sections allow the pitch to be condensed, allowing more audio to be crammed onto the disc.

Anticipating the audio dynamics obviously requires a look‑ahead facility, created by introducing a delay into the audio path to the cutter head, and that delay is typically about a half revolution, or 900ms for a 33 1/3 LP. Traditionally, that delay was achieved by fitting the mastering reel‑to‑reel tape player with an extra ‘preview’ head near the supply reel early in the transport path before the proper replay head. However, from about the mid‑’80s many disc‑cutting systems starting using a digital delay line in the audio path instead, particularly if the mastering source was already a digital file from an early DAW system. When this solution was employed, analogue records were actually cutting a digital signal... but that’s a discussion for another article!

Regardless of how the preview signal is obtained, it is used to adjust the pitch rate of the groove in a dynamic way. However, since any movement of the replay stylus generates a sound output, the rate of change of the groove pitch has to be slow and gentle enough that it is effectively sub‑sonic and thus not audible — if pitch changes happened too fast they would result in an audible wow or musical pitch variation, which is what happens if the spindle hole is off‑centre. So, the SimuLathe software therefore has two signal paths called Mod and Pre. Mod is the (delayed) audio path to the virtual cutter head, while Pre is the preview signal used to drive the pitch system.

Another important aspect to consider is the recorded wavelength on the disc. Since vinyl discs rotate at a constant, fixed speed (33 1/3 or 45 rpm), the start of the disc at the outer edge has the vinyl material travelling quickly beneath the cutter head, so the recorded wavelengths are relatively long even at high frequencies, and the rates of change along the groove walls relatively gentle. As the track nears the inner edge the recorded wavelengths are necessarily much smaller and the rates of change on the groove wall much faster. These changes, called the diameter effect, restrict the audio bandwidth and dynamic range, which must also be taken into account in preparing the audio tracks. (Incidentally, it might be worth contrasting this variable pitch, variable linear speed, outside‑to‑inside format with that of the CD, which has a fixed pitch and constant linear speed, with the laser tracking from inside to outside.)

In Use

The first thing to specify in the plug‑in is the type of disc you wish to cut: there are options for a 7‑, 10‑ or 12‑inch disc, and 16 2/3, 22.5, 33 1/3, 45 or 78 rpm speeds. Given the disc size and the default track pitch setting, the software estimates the available time and disc usage, but these numbers will be updated once the audio is properly analysed, with the dynamic pitch variations and other parameters.

When used as a plug‑in in most DAWs, SimuLathe will integrate with the DAW timeline play position marker, so once the start and end time of the track is logged in the data boxes at the top left of the main window, the plug‑in can relate the groove cutting parameters (and, more importantly, any infringements) to identifiable points within the track itself. Some DAWs aren’t able to integrate fully, but there are various manual and automated workarounds, all clearly explained in the manual.

With the basics set up, next comes the fun of juggling audio parameters to optimise the final record cut, starting with Input Gain and Stereo Width. These controls run down the centre of the GUI, and can be operated like knobs or specific numeric values can be entered directly. The gain needs to be as high as possible to give the best signal‑to‑noise ratio, but high levels will create wide grooves that can be difficult for a replay stylus to track, and use more disc surface area, thus reducing overall playing time capacity. Greater stereo widths also affect groove geometry, of course, so that may need to be fine‑tuned. To help with both of these aspects, there is a stereo average/peak level meter and a phase correlation meter.

The Ref version simplifies some aspects that might confuse those who haven’t operated real lathes — but it still offers plenty of control.

Further audio processing in the Ref edition includes high‑ and low‑pass filters as well as the so‑called ‘elliptical’ filter, all arranged on the left‑hand side of the display. All three filters have adjustable turnovers and slopes. If the elliptical filter sounds mysterious, it’s really just a high‑pass filter which only affects the Sides signal derived from a stereo input. It is used to force bass content into mono, which helps to control the groove width and depth.

The effect of all of these audio signal processing parameters on the nominal cut groove is displayed on a Geometry graph at the bottom of the window, which also gives estimates for the peak velocity and excursion, as well as the groove width range.

In the full‑fat Cut edition, the Geometry graph is replaced with three parameters. These are three intelligent limiter functions, acting to control the maximum excursion, groove width and velocity, and all have adjustable thresholds, attack and release parameters as well as individual gain‑reduction meters.

The right‑hand side of the GUI mostly comprises meters showing the lathe activity. There are indicators here for the track pitch, groove width and velocity, with separate readouts showing peak values. Under a spanner symbol, options are presented for configuring the lathe with variable or constant pitch, and standard or deep grooves, and all measurements can be displayed in metric or imperial values. So pitch is expressed in Rillen per millimetre (R/mm) or lines per inch (LPI), for example, and groove width in µm or mil. Velocity is always shown as cm/s. An interesting fact to ponder here is that the groove width indicator also infers the groove depth — since the cutter has a 90‑degree profile, the width is always twice the depth!

The SimuLathe emulation offers the unique ability to accurately assess peak velocity for the first time, which will be a great asset to professional mastering engineers.

High groove velocities are a serious problem for both the cutter head and the replay stylus, and thus need to be carefully controlled but, historically, these have been impossible to measure during cutting. The SimuLathe emulation offers the unique ability to accurately assess peak velocity for the first time, which will be a great asset to professional mastering engineers. Related to this issue, the software also estimates the cutter head temperature and the head currents in each audio channel. Typically, temperatures over 200C and currents over 1.5A will cause circuit breakers to activate in most systems to automatically protect the (expensive) cutter head, so these parameters give an idea of how much risk is being taken!

Further numerical readouts indicate the amount of likely harmonic distortion for the selected replay pickup type, the signal‑to‑noise ratio, and the cutting level expressed as both peak and VU meter values. The emulation of replay characteristics is impressive, with three generic pickup types. The hi‑fi option is based on a MicroRidge stylus, the mid‑fi uses an elliptical stylus, and the club option replicates a heavy‑duty elliptical stylus. Typical record and arm/cartridge defects can also be introduced including erroneous tracking angle, disc wear, clicks and crackles, and system noise. Sadly, there’s no built‑in facility to output an audio file of the simulated vinyl sound — I can anticipate many potential users being interested in that — but you could re‑record the monitoring output in real time if you wanted.

A separate Disc Stats window provides three information areas to assess whether the track can be cut efficiently and what the optimum lathe settings and audio pre‑processing parameters should be. Dominating the stats window is a 3D view of the virtually cut grooves across the disc, with the ability to zoom in and rotate the disc to examine any particular groove at any particular position. Any areas of concern can be highlighted to aid navigation, too. There’s also a graphical waveform view (with timeline zooming) which, again, indicates groove excursion, groove width, velocity and land (the area between grooves) ranges, with highlighted areas of concern. And finally, there’s a numerical table showing absolute min and max values.

The disc statistics and groove view, shown here for the Ref version.

Impressions

SimuLathe is a fabulously detailed emulation of a real disc cutting lathe, with all the tools and parameters of a mechanical cutter. Whether your interest is simply to learn something about the process and challenges of cutting a record, or as a professional mastering engineer wanting to trial and optimise alternative cutter settings without risk or expense, SimuLathe is the solution in either the Ref or Cut editions. And for those not sure if the cost is justifiable, the demo version will answer that question. I am very impressed by the depth and precision of the emulations, and I learned a great deal about the technical and aesthetic trade‑offs that must be made in order to realise a workable, playable vinyl disc. Perhaps not all of the black magic arts of vinyl cutting have been revealed to me, but I certainly have a much better overall understanding and appreciate the work of experienced lathe engineers so much more.