Vintage

Tonearm and belt-drive aside [see below], the rumble performance of the BDS 80 was significantly under-rated by BSR. Specified as better than –55dB (DIN 45 500), in practice the steel/phosphor bronze (ball) bearing was capable of a mere –69dB rumble (DIN-B wtd, re. 1kHz/5cm/sec), putting the BDS 80 on a par with many a modern deck. Through-groove rumble, assisted by the thick rubber mat, was similar at –68.8dB. Speed stability was less impressive, however, for though BSR used a four-pole synchronous motor, this was a high speed unit coupled to the belt via a narrow spindle rather than the more substantial pulley used in today's decks [visible at 9 o'clock in the overhead picture, p125]. Absolute speed error was high at +1.5% and wow & flutter poor at 0.28% [see Graph 1, below]. Hence the 'belt-drive wobble and slightly watery texture' reported by our reviewer, Tim Jarman, during his listening tests.

The partnering tonearm has a rigid, square cross-section alloy tube and a compact counterweight assembly, but the large headshell is composed of a thin alloy plate and plastic. While this serves to keep the overall effective mass down below 10g, suiting the high compliance MMs of the day, it also brings some unwanted flexure to the arm as a whole – in practice close to 20-30Hz with other low-Q modes at 85Hz and 140Hz [see Graph 2, below]. The higher-Q resonances at 290Hz and 495Hz appear to emanate from the arm bearing and auto-cue structures where there is evident play in both horizontal and vertical directions. Friction is higher than average too at ~50mg. We now know that the next 10 years would see a significant evolution in the design of both turntables and tonearms. PM