Behind the Design of the New C 558 Turntable

With Record Store Day this month, we sat down with NAD’s Chief Technology Officer, Greg Stidsen, to talk about NAD’s new flagship turntable, the C 558.

The NAD C 558 traces a long lineage of innovative, high performance turntables that bring records to life. While the basic operation of a turntable seems simple, extracting all the musical energy from the record grooves without exciting destructive resonances requires both science and art. Here we’ll take a closer look at each of the elements of the C 558 with an explanation of the choices we made.

1) Speed Accuracy

Having exact pitch (speed) is important. However, human hearing is much more sensitive to momentary changes in speed, which we express with the terms “Wow” and “Flutter.”

The C 558 addresses both of these problems with a specialized, high precision, synchronous clock motor that is both smooth and accurate, especially when driven from a stable AC voltage. To ensure a clean and stable AC voltage, we isolate the AC Mains by first converting it to a clean DC voltage, and then electronically generating the precise AC frequency to regulate the synchronous motor. Using a specially formulated belt to drive the platter further filters and isolates any remaining vibration. All rotating parts are machined to very tight tolerances to eliminate any eccentricity or vibration in the drive system, ensuring you get the best possible performance from your NAD turntable.

2) Tracking Geometry

Because records are round they create some interesting problems for tonearm engineers as the angle of the tonearm, and thus the tracking angle of the stylus, change as the arm moves from the outside of the record to the inside grooves. If the stylus is not perfectly aligned with the groove at all positions on the record, the result is audible distortion and increased record wear.

Thankfully, the C 558 uses a longer than usual 9” tonearm to optimize overhang and reduce the tracking angle error. To perfectly align the stylus we also include adjustments for azimuth and vertical tracking angle, and include a gauge to calibrate the alignment.

3) Built with Precision

To fully realize the micro-dynamics of music requires a tight mechanical coupling of the platter and the tonearm. This forms a triangle, as vibrations can travel from a record being played to the platter, through the shaft and bearing to the base (plinth), up the arm mount, through the arm pivot and down the arm to the cartridge and stylus. There are many separate parts in this path and some of them are required to move relative to one another through mechanical bearing interfaces. If there is any play in these mechanical interfaces, musical energy will be lost.

This is why NAD has paid special attention to precision machining, assembly, and testing that is so important in a turntable.

4) Resonance Control and Isolation

Reducing all spurious vibrations to a minimum is critical to getting the best result when playing vinyl. Since these vibrations can come from various sources, both internal and external, the materials and dimensions must all be carefully calculated so that they may reduce and balance all the resonances to prevent a buildup of energy at particular frequencies.

To isolate external vibrations from the loudspeakers or footfalls bouncing the floor, we use a massive MDF base with specially tuned vibration damping feet, along with a thick non-resonant dust cover. The choice of glass platter, felt pad, MDF base, and aluminum alloy tubular tonearm, were carefully considered to work together to limit and reduce spurious vibration.

5) Detailed Engineering

They say a great chef can make delicious food from very basic ingredients, while a cook without training can make a mess of even the finest and most exotic ingredients. NAD is a five-star chef in the audio world, designing award-winning products for over 45 years now. We think the C 558 hits a sweet spot for performance and value by using very simple, high quality parts and precisely engineering them to work together in perfect harmony. We believe the result to be a feast for the ears that will last for years, and ultimately bring new life to your existing record collection while preserving it for the future.

Sign up now to join our Record Store Day event at the Toronto Reference Library