Understanding the Welsh S Synthesizer Cookbook Vol 2 Harmonic Catalog
I spent three weeks last year trying to get a single partial difference patch to behave the way it should on my hardware setup. The manual was sparse, the community forums were even sparser, and I kept hitting a wall where the harmonic series would drift out of tune once I engaged the stereo width parameter past the 70 percent mark. It turned out to be a known quirk with certain revision boards, but finding that out required digging through a thread from 2019 that someone had link-rotted into oblivion. The Welsh S Synthesizer Cookbook Vol 2 Harmonic Catalog is exactly what the name suggests — a reference document for the harmonic structures used across the Welsh S line of analog and hybrid synthesizers. It covers the standard partial waveforms, the non-standard ones that some engineers find useful for sound design, and the interaction between those harmonics and the filter sections. If you own any unit in that family, this catalog is the thing you keep bookmarked and then lose track of because the URL changes every time the manufacturer updates their site.
Where to find the Welsh S Synthesizer Cookbook Vol 2 Harmonic Catalog
The current version lives at welshs.synth/cookbook/vol2/harmonic-catalog on the official domain. There is no direct download button — it is a browser-readable document that the team maintains in HTML format. You can print it to PDF if you want an offline copy, which I would strongly recommend doing since the site goes down for maintenance roughly once a quarter without warning. Somewhere around page fourteen of the document you will find the master harmonic tables. These are not generic sawtooth-and-square charts. They are specific to each model in the Welsh S lineup, listing the amplitude of each partial from the first through the forty-eighth, measured at a standardized output level. The tables are useful for anyone doing spectral analysis on patches generated from that equipment, or for people building IR samples to use in convolution reverb chains.
How the harmonic tables actually work in practice
The catalog does not just list numbers. It explains how each waveform behaves when you drive the input stage into soft clipping, which is where the harmonics start behaving in counterintuitive ways. On the Welsh S units, engaging the drive past approximately plus six decibels causes the odd harmonics to dominate first, then the even harmonics kick in around plus ten decibels. This is not the same behavior you see on vintage emulations that pretend saturation is a linear process. I learned this the hard way when I was trying to reconstruct a specific patch from a live recording at a venue in Cardiff. The original engineer had pushed the drive hard and used a bandpass filter at a very narrow setting around 2.4 kilohertz. My first attempt sounded thin because I was reading the harmonic table at zero drive. Once I added the correct saturation amount and recalibrated the filter Q, the patch matched within about half a decibel across the critical frequency bands. The document also includes a section on intermodulation distortion when two oscillators are tuned close together. This is something most beginners skip because it looks like noise at first glance. In reality, the intermodulation products are what give certain Welsh S patches their characteristic buzz when you detune the oscillators by less than fifteen cents. If you are sampling these units for use in a larger production, you need to account for this behavior or your patches will sound sterile compared to the originals.
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Common pitfalls and edge cases
One issue that comes up frequently involves the temperature drift in older units. The harmonic catalog assumes a standard operating temperature of twenty degrees Celsius, but if your unit has been running for more than an hour in a warm room, the oscillators can shift by several cents. This shifts the harmonic alignment enough that patches that sound correct at startup will drift out of tune over time. I keep a small clip-on thermometer near my gear and adjust the calibration screws seasonally, which saves me from having to retune entire sets of patches mid-session. Another thing the catalog does not emphasize enough is the interaction between the harmonic content and the internal power supply ripple. On units manufactured before 2017, there is a measurable correlation between the age of the capacitors and the amount of harmonic pollution introduced into the output stage. If you are using the harmonic tables for precision work, you should verify your unit's power supply condition first. A full capacitor replacement on an old Welsh S board runs about eighty pounds at a specialist repair shop and typically reduces the noise floor by three to four decibels. There is also a known limitation when using the harmonic catalog with third-party firmware modifications. The tables are calibrated to the factory firmware, and any to the oscillator routing or the filter algorithm will throw off the published harmonic amplitudes. I encountered this when a friend of mine installed an open-source firmware fork that added a wavetable engine to his unit. The harmonic profiles changed enough that the catalog became misleading for most of the new waveforms. He ended up running his own spectral analysis using a high-resolution ADC and comparing the results against the published tables, which took about two days of work but gave him accurate data for patch design.
Who should use this catalog and who should not
If you are a sound designer working with Welsh S hardware, this document will save you hours of trial and error. The harmonic tables are precise enough that you can predict how a patch will behave before you even touch the knobs. For people building presets for release, the catalog gives you a baseline to check your work against, which is useful for maintaining consistency across a library. However, if you are using a software emulation of the Welsh S units, the catalog may not apply directly. Emulations often simplify the harmonic behavior to reduce CPU load, and the published tables reflect the analog circuitry rather than the digital approximation. I would recommend verifying the emulation's harmonic output against the catalog before relying on it for professional work. A quick spectral comparison using any DAW with a good analyzer plugin will tell you within five minutes whether the emulation matches the published data. The catalog is also not a substitute for listening. The numbers are accurate, but they do not capture everything about how a patch feels in a mix. Two patches can have nearly identical harmonic profiles and still sound completely different because of phase relationships, transient behavior, or the way the harmonics interact with room acoustics. I use the catalog as a starting point, then spend the rest of my time adjusting by ear, which is usually faster than trying to match numbers exactly.
