Because vinyl recording and playback systems follow the RIAA standard, it’s easy to think that cutterhead EQ is just about applying the inverse RIAA (iRIAA) EQ curve and getting cutting. In reality, especially with dynamic (non feedback) cutterheads, it doesn’t work like that. Dynamic heads don’t behave in a perfectly predictable way, and their response is massively influenced by the head design. So relying on a generic iRIAA EQ curve never gives accurate results.
The best approach is to map your own cutterhead and build a custom EQ based on how it actually behaves. This means identifying resonances and the heads natural frequency response, whilst also taking into account your diamond stylus type and the physical length of the diamond. This is called a ‘feedfoward’ system.
Here is a guide on how to do this:
Step 1: Make Sure Playback is Calibrated
This step is critically important, you must ensure that playback is calibrated to the 0 VU reference level using a professional test record.
Step 2: Cut Audio Without EQ
First, ensure you have appropriate audio for this task. Do not use a noise profile such as pink noise as it will not expose the heads resonances sufficiently, use program material that is specifically mastered for vinyl and has a well balanced frequency spectrum. This is crucial, as the quality and characteristics of the audio will directly impact the accuracy of the final EQ curve. Pink noise can be used as a final reference check, but we recommened using music as it is better for exposing the heads resonances.
The next part will be cutting a disc without any EQ, this has to be carried out with caution. If you accidentally send too much audio signal you could blow your fuses and, in the worst cases, damage your cutterhead.
You are now ready to cut the audio. Start with your volume right down sending no signal at all, start to cut at 45 RPM on a 12" disc, monitor the cut with your tonearm, then SLOWLY raise the volume until cutting at 0 VU on your calibrated playback level meter. This volume level is crucial, which is why accurate playback calibration is essential. Cutting at around 0 VU without corrective EQ will get the cutterhead to exhibit its distortion profile and reveal its natural and mechanical resonances. We want to stress, this needs to be carried out carefully, exactly as we described and calibration MUST be right before considering cutting.
Step 3: Record Audio
Next, record the audio from your cut back into your DAW as a 32bit or 24bit WAV/AIFF file. If you don’t have access to a high end stylus, we recommend using a Audio Technica VM95-ML, as these are well priced and provide reliable performance at the very least. At this point, the audio will sound muddy with a distinct lack of high end, this is normal.
Step 4: Make Your Custom EQ
For this process, we recommend using an EQ with a good Match EQ function, unlimited bands, and various band shapes. We use Toneboosters Equalizer Pro, which provides all the necessary features, isn't too clinical and sounds musical in our opinion. Another great EQ for this is Tokyo Dawn Nova GE.
Start by aligning your recording with the original audio in your DAW so you can A/B compare them side by side. Ensure both files play interchangeably and have matched volume levels. Since your recording might have little high end information, adjust the volume by listening to the low end to balance it with the original, so both tracks' low ends are at similar volumes.
Next, use the Match EQ function with the original file as the reference. Create a 1 minute loop to ensure both files play identical audio into the analyser, then match the EQ.
Before cutting a new disc, apply the EQ to the original audio by using an instance of your EQ plug in on your mix bus. To prevent digital clipping due to the EQ's high end boost, normalise your audio to -27 LUFS if using a Vinyl Recorder or MC-02, or -30 LUFS if using a DinSync NC-V8. Apply this normalisation to all audio files before cutting in your DAW to keep them at a consistent volume level that avoids overloading the plugin. This also calibrated your cutting chain as all audio will be roughly the same volume before cutting.
Step 5: Repeat
The key here is repetition. Cut the same original audio through your cutterhead EQ and record the playback back into your DAW. EQ match the result against the original, then cut again with the updated EQ as a secondary instance of the plug in. Repeat this process, adding additional instances of your cutterhead EQ plugin in series if needed, it's common to end up with three or four instances stacked in a row before the playback recording closely matches the original file. Each pass gets you closer. If your original audio is mastered well and suitable for the task, along with the cutting volume being right to expose the cutterhead’s resonances, you should be able to get the head performing to its full potential.
Step 6: Done!
You should now have well balanced cuts that significantly enhance your system's performance.