PHOENIX ENGINEERING ROADRUNNER DIGITAL TURNTABLE TACHOMETER
The RoadRunner is a microprocessor controlled digital tachometer used for monitoring turntable platter speed to 3 decimal places of resolution. The internal time base is a temperature compensated crystal oscillator (TCXO) accurate to 2.5 PPM (±0.00025%) with less than 1.0 PPM aging per year.
The RoadRunner Tachometer provides a direct digital readout of the platter speed after only 2 revs and updates the display on each revolution afterwards. This provides a significant improvement over strobes and other devices (i.e. Sutherland Timeline) that are only indicators of fast/slow, not a measurement device. Strobes also lack resolution; often you need to track the "drift" of the marks over several minutes and compute the speed using a calculator. At 33 RPM, a speed error of 0.01 RPM represents a drift of 0.0113" per revolution (about the thickness of card stock).
The tachometer uses a Hall Effect sensor and a small magnet attached to the underside of the platter to sense the platter rotation. The sensor requires approximately 0.25" (~6mm) of clearance to be installed properly. The magnet/sensor assembly can be installed under the platter at the edge or under a sub-platter assembly if present.
The RoadRunner Tachometer can be connected directly to the Falcon digital Power Supply Unit or to the Eagle 15 watt Hi-Power Power Supply Unit (each sold separately) via a 3 wire serial cable in order to synchronize its output with the direct measurement of the platter speed. Operation is completely automatic with no user intervention needed. The tachometer outputs the speed reading once per revolution. The PSU compares this reading to the speed on the display and can make micro-fine adjustments to the output frequency to lock the turntable speed to within ±0.005 RPM. The adjustment is done slowly and evenly over the entire next revolution and is inaudible to the listener (in most cases, the adjustment is <0.0005 RPM per step). The turntable remains on speed independent of the belt tension, bearing oil viscosity, drag from the needle or any other variables that cause the table to drift over time.