Excalibur 3 arm — www.townshendaudio.com

To achieve accurate replay of vinyl LP, it is common sense to make the record player as rigid as possible so as to mimic the massively strong record cutting lathe as closely as possible. It is relatively simple to make the turntable / platter / bearing assembly extremely strong and rigid, but the pick-up arm is another matter. If the pick-up cartridge is not held as rigidly as possible by the pick-up arm, the modulations in the record groove (the music) will cause the cartridge to wiggle in sympathy with the music. Just imagine a stationary record with the needle in the groove with the cartridge wiggling from side to side. Inevitably, an audible signal will be reproduced in the speakers. So, when the record is playing, it is imperative that the cartridge must be held “still” at audio frequencies to prevent the addition of this unwanted sound. (Some naive listeners like this sound as it adds a sort of extra echo that makes the sound more reverberant).

Many arms are manufactured which are not rigid. In some cases, the arm manufacturer takes pride in the flimsily nature of their product – the use of thin, curved arm tubes which can easily bend, the use of flat light-weight head-hells which can flex, the unipivot which can rotate around the axis of the arm-pipe, the use of very soft, compliant coupling between the cartridge and head-shell, the use of very weak materials in the arm-pipe – the list is long and the range of different sounds from arms is well documented, hence the term “tone-arm”.

In the case of Excalibur 3, great pains have been taken to make the arm as rigid as possible to eliminate the afore-mentioned problems so as to achieve as accurate a replay as possible. The head-shell comprises a space-frame machined out of two solid billets of pure magnesium, chosen for its exceptional lightness, stiffness and most important of all, its astonishing self-damping which is way above that of other engineering materials. The space-frame is held together with stainless steel micro-screws, spaced with four ultra-thin-walled stainless steel tubes.

The arm-pipe is made of large diameter very thin-walled stainless-steel tubing for great stiffness, strength and lightness, which is much stronger than aluminium tubing of similar mass. The arm-pipe is then filled with rigid polyurethane foam to add extra stiffness and, most important of all, enormous damping to seriously suppress ringing.

The connection between the head-shell and armpipe is by way of a scarfed joint as opposed to the usual butt joint, again for rigidity. Further, this form of attachment extends the cylindrical rigidity of the arm-pipe as close as possible to the area where the cartridge is mounted, there being as short a path length from the arm-pipe to the cartridge as practical, with a long area of connection to the arm-pipe. This ensures the least amount of flexing as possible. The attachment between the arm-pipe and head-shell is by high-strength glue and three micro-screws, resulting in an enormously strong, light-weight structure.

Further, the Excalibur arm at 220mm is typically 10 to 20mm shorter than most conventional 10” arms and much shorter than the increasingly popular 12” arms. This is counter intuitive with regards distortion due to tracking angle error, but the trade-off between the reduction in stiffness and its associated distortion due to bending of a long arm vs the increase in stiffness of the shorter arm with optimum geometry by the ideal choice of overhang and offset employed in the Excalibur design results in a vastly superior result. For full details of the theory behind this optimization, see CRANFIELD INSTITUTE OF TECHNOLOGY, DEPARTMENT FOR THE DESIGN OF MACHINE SYSTEMS .

In the case of the Excalibur 3, the rear end of the arm-pipe is rigidly connected to the very well-engineered back-end of the Rega RB 300/301 arm resulting in a superb sounding arm at a reasonable price that will fit all Townshend Audio Rock turntables with the appropriate arm-plate – please specify on ordering.

The internal wiring terminates in a standard five pin modified DIN plug in the arm-base that will connect to all standard plug-in arm cables. For ultimate performance, a special version is available wired internally with Townshend Audio’s new proprietary and secret “Fractal” wire.

The icing-on-the-cake is the unique front end damping exclusive to the range of Townshend Audio Rock turntables. The diamond shaped head-shell has the damping paddle mounted to it extremely rigidly, again by very strong stainless steel micro-screws. The fluid coupling between the paddle and trough locks the front end of the arm, and hence the cartridge, to mechanical ground at audio frequencies, 20Hz and up.

The 8-12Hz arm/cartridge resonance combined with the very high low-frequency gain of the RIAA equalization, results in a signal typically 25dB higher than the audio signal in the case of the un-damped arm. This huge subsonic signal causes non-linearity in the cartridge generator, overload distortion in the preceding amplifier stages, huge circulating currents in the output stage of the amplifier severely limiting output, especially with valve amplifiers, and enormous bass-cone excursions frequently visible when playing vinyl. With the damping trough in place, the horrendous 25dB peak is reduced to -3dB at 10Hz. Further, the response at 20Hz is reduced from +4dB to 0dB and the response at 100Hz is reduced from +1dB to 0dB with the use of the trough. The behaviour at 2Hz is identical to that of an undamped arm, so the response of the Excalibur 3 arm to record warps and the 2Hz wobble (due to the four leafed clover shape of a vinyl record caused by unequal cooling of the four steam/cold-water pipes in the record press) is unaffected.