If you’ve ever tried to fine tune your stylus azimuth, you know that it’s not that easy. While the process might be fairly straightforward, in practice getting good results can be tough even for people that know what they’re doing.
Azimuth alignment involves optimizing both the physical azimuth for best groove contact and electrical azimuth for highest signal strength.
The needle has to sit properly in the groove — physical azimuth is the mechanical rotation about the arm’s axis (roll axis). Proper physical azimuth puts the cantilever axis perpendicular to the record surface so the stylus sees left and right groove-wall motion symmetrically, controlling how the stylus contacts the two groove walls. Physical azimuth strongly affects distortion, channel balance for groove-derived (vertical) information, imaging, and record wear.
Given the high performance stylus designs available today, a correct azimuth alignment is even more important. Christiaan Punter wrote a great article for HiFi Advice covering many of these advanced designs and their attributes.
Once the physical azimuth alignment is set, you can measure and optimize the electrical azimuth / electrical output: the separation between left and right stereo signals and minimize signal leakage (crosstalk). Tools for this include test records (ie. The Ultimate Analogue Test LP, Side 1, Track 1, Track 2, and Track 3) and devices like a Puffin, Fozgometer, or AnalogMagik software, to determine actual channel balance. The best electrical azimuth may not look perfectly upright but gives the truest stereo image and channels separation. Electrical azimuth calibration is recommended for precise channel separation and stereo imaging, as the physical look may not always match the internal coil alignment.
Caveat: If the stylus and cantilever are physically out of alignment from the factory and not within the manufacturer’s tolerances, a few problems will occur:
One channel will be more sensitive to vertical groove motion than the other → channel level/tonal imbalance on certain material;
Inter-channel phase/phase-response errors increase → smeared imaging and poor mono compatibility (some frequencies cancel when summed);
Increased harmonic distortion, mistracking, and uneven record/stylus wear (this causes physical, permanent damage).
You can’t correct bad geometry with electronics — electronics will only mask the symptoms (EQ/gain) but it cannot restore correct stylus/groove geometry or prevent abnormal groove wear.
The Two Step Calibration Process
Basically, there’s two approaches to setting stylus azimuth - visually and electrically. Both are important. Assuming that the stylus and cantilever have been manufactured correctly (which is actually a big assumption), and the coils inside the cartridge are correctly positioned, the best way to calibrate stylus azimuth involves a two-step process.
The first step is to visually align the cantilever so it is perpendicular to the record surface (you can use a mirror under the cartridge to see if the cantilever and its reflection form a vertically straight line perpendicular to the record surface).
The second step involves adjusting the electrical azimuth. This step focuses on channel separation and crosstalk — the leakage of signal from one channel to another. Measurement requires a test record, voltmeter, or specialized electronic tools (e.g., Puffin, Fozgometer, software), listening to or measuring one channel while only the other is modulated.
The optimal setting is when crosstalk is minimized and both channels are evenly balanced for the best stereo separation (even if the cartridge or stylus may look "tilted" visually).
Because the internal structures of the cartridge (such as the coils, yoke, and cantilever/stylus) may not visually align with the cartridge body, only electrical measurements can ensure true channel balance and separation at playback.
The Issue
The main issue with this two-step calibration process is that it requires several “test-set-test” cycles and makes it difficult to determine the best signal performance for each channel because of the need to repeat and reconfirm the last test.
“There’s got to be an easier way to do this . . . “
So I figured, if Micro Seiki did it with dynamic VTA and dynamic VTF, maybe it’s possible to dynamically set the azimuth while a record is playing. Then you could actually see in real time the peak signal strength and maximum db while playing a 1kHz test track — without taking the needle out of the groove to readjust the headshell.
My Solution
Solving this engineering puzzle required using a stabilized unipivot bearing that would allow adjusting the roll axis of the stylus and cantilever independently from the pitch axis and the yaw axis — while retaining frictionless pitch and yaw freedom of movement as the record is playing.
The offset angle of the headshell matches the offset angle of the bearing which is dependent on the effective length of the arm’s stylus to pivot distance. Also, the stabilzed unipivot bearing is positioned on the same horizontal plane as the record groove. This arrangement allows the stylus azimuth to have the correct geometry when making azimuth adjustments from a rotary control on the stabilized unipivot.