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Phoenix Engineering Eagle PSU and RoadRunner Tachometer

Phoenix Engineering Eagle PSU and RoadRunner Tachometer

Bill Carlin of Phoenix Engineering, LLC, has created two very useful accessories for turntables. The first is the RoadRunner digital tachometer ($235) which can be used on any ’table to precisely measure the speed in real-time of each rotation of the platter. The second product is the Eagle PSU ($525), a high-power, digital turntable power supply that controls the turntable speed, if the turntable uses an AC motor that derives its rotational speed from the wall plug’s 60Hz (or 50Hz) frequency. When the RoadRunner and Eagle PSU are combined in a system that can use both, the accessories form a fully automatic closed-loop speed controller that creates long-term speed stability and compensates for drive-system irregularities.

With the RoadRunner, the speed setting of any turntable can be observed in real-time all of the time. Installation is fairly straightforward. A small rare-earth magnet is attached via its adhesive side to the edge of the platter. The magnet weighs approximately 0.10–0.12 grams, which is less than 3%–10% of the tracking force of most cartridges; so there should be no concerns about the weight of the magnet disturbing the platter balance. The RoadRunner tachometer is attached to its sensor board via a supplied cable. The sensor board is placed on the plinth so the magnet passes within ¼” (or closer without touching) of the on-board Hall Effect sensor to trigger detection. Once the RoadRunner is powered up, the display will show five dashes and the sensor detection can then be verified by rotating the platter until the magnet is directly over the sensor. When this occurs, a sixth dash will appear on the display verifying proper installation. All that’s left is to start the platter and view the RoadRunner display once the ’table is up to speed.

Phoenix Engineering Eagle PSU and RoadRunner Tachometer

At the heart of the RoadRunner is a microprocessor that is driven by a temperature-compensated crystal oscillator (TCXO) with +/-2.5ppm (+/-0.00025%) frequency stability. The displayed speed of the platter rotation is measured to 0.001rpm resolution. The ability to see a real-time digital speed indication of platter rotation under any condition (unlike most strobe-like devices) is a key advantage of the RoadRunner. With this ability, the effect of the entire drive-system tolerances (belt thickness, tension, slippage, creep, pulley-step ratios), warm-up times (bearing, belts, motors), and drag forces (from different mats, clamps, outer rings, and the stylus) are all revealed by the changes in speed displayed by the RoadRunner.

After several hours of in-house observations, I created a test procedure that allowed me to record the performance of several turntables at remote locations. The procedure entailed measurements during 15 minutes of turntable warm-up and an additional 5 minutes of rotation after the LP was placed on the record, complete measurements of beginnings and endings of songs on an entire LP side, and a few minutes of measurements of the LP runout groove. These steps were followed by an additional set of 2-minute measurements with the stylus removed from the record and then with the LP removed from the platter.

Using this test procedure, I tested 13 different turntables (Acoustic Signature, Basis Audio (3), Grand Prix Audio, Kronos Audio, Nottingham Analogue, SME, TW Acustic (2), VPI, Walker Audio, and Wave Kinetics) with the RoadRunner tachometer alone. All but two direct-drive units and one closed-loop (speed read and adjust) belt-drive unit were subject to system tolerances, warm-up times, and drag forces to one degree or another. Of all the variances, stylus drag had the biggest and most consistent effect; it also had some variance at the beginning vs. the end of the record. (Tip: In most cases, when setting turntable speed, it is best to set the speed with the stylus in the grove playing a record if possible.) With the RoadRunner monitoring the speed, ’tables with the ability to adjust speed could be set for optimal conditions with the stylus playing a record.

The Eagle PSU is a 25-watt AC-voltage-regenerator motor-controller/power supply with speed adjustment of +/-1.0rpm in 0.01rpm steps. The Eagle features automatic voltage reduction (level selectable during calibration) for each speed, a soft start to lessen the stress on drive belts, ability to startup in 33.3 or 45.0rpm mode, speed calibration modes, jumper selectable 115VAC or 230VAC output voltage, 100–260VAC/50Hz/60Hz input voltage, operating-pulley selection mode, and a third speed range selection (untested during the review) for 78rpm records, if the turntable has the correct pulley, with a wider range of +/-6.0rpm in 0.1rpm steps.

 

The Eagle is a two-piece unit with the smaller controller housing the frequency generator, user interface, and logic circuits. On the front panel of the control unit, there are three control buttons (–, +, and STBY) and a display. In normal operation, the “STBY” button cycles between 33.3rpm, 45.0rpm, and standby (motor off) mode when pressed and held. The larger remote amplifier boosts the small signal from the controller to create the 115VAC (or 230VAC) output. One benefit to the two-piece configuration is the ability to place the signal-boosting amplifier away from the cartridge, tonearm wires, and phonostage input to keep AC-generated 60/50Hz noise away from the low-voltage audio signal chain.

Like the RoadRunner, the Eagle is also microprocessor-controlled with modes for standby, sleep, normal operation, voltage calibration, and factory default programming. Carlin mentions that the Eagle is the only commercial PSU to use Direct Digital Synthesis (DDS) technology to create the sinewave for AC regeneration. He also feels other PSUs that are based on Phase Locked Loops (PLL) can have issues with frequency wobble and poor resolution while those using Pulse Width Modulation (PWM) can suffer from poor resolution as well. The DDS function generator is a 28-bit device that feeds the digital signal to a 10-bit voltage output DAC. Technically, the spurious content is reported to be below -60dBC, since the highest frequency output is around 81Hz. The DDS is claimed to generate a clean sinewave with less than 0.04% total harmonic distortion (THD). The minimum step size of the frequency generation is 35µHz—small enough to make adjustments during playback without the changes being audible (more on this later), which is where PLL and PWM can have poorer performance due to the issues Carlin mentions above.

The Eagle PSU and RoadRunner are designed to form a closed-loop system when connected together. There is a single cable interface between the units that allows the RoadRunner to transmit the platter-speed calculation to the Eagle. The Eagle monitors the turntable speed, and if (and only if) long-term drift is outside of a specified error window (unique to each speed setting), the correction is calculated and applied by the PSU within the rotation using the small frequency steps mentioned above. When this correction is being applied, the Eagle’s display will “blink” the decimal point to indicate the function is being implemented. Carlin told me that the corrections will be fewer as the system warms up and stabilizes, and that is what I observed on the six ’tables that could be tested with the complete Eagle/RoadRunner system.


Phoenix Engineering Eagle PSU and RoadRunner Tachometer

Six of the thirteen turntables mentioned above were subjected to a second round of testing (using the same test procedure mentioned above) with the complete Eagle/RoadRunner closed-loop system. All six ’tables showed improved measured results yielding stability within the specified window of +/-0.005rpm under all conditions. The improvement in measured performance due to negating speed-stability variances of turntable tolerances, warm-up, and drag forces was remarkable. Every one of the turntables showed measured speed results that were between 33.330 and 33.338rpm worst case, with the majority of the readings between 33.333rpm and 33.336rpm.

The RoadRunner, by itself, gets a high recommendation for its real-time speed-calculation and display. Whether the Eagle can be used with the ’table or not, the RoadRunner serves a useful function of reporting speed during actual playback under all conditions. It has earned the right to be a tool for my usage during normal turntable playback, reviewing, or setup. Coupled with the Eagle PSU, the combination produces near rock-solid speed control of the turntables that work with this complete system. In listening tests, there were no audible downsides; the Eagle/RoadRunner system’s speed-control implementation only brought peace of mind and a touch of convenience. This combination is also highly recommended if the turntable can use both.

SPECS & PRICING

Roadrunner
Type: Digital tachometer
Case: One-piece extruded aluminum
Operating modes: Standby, sleep, normal
Power requirements: DC Supply 9VDC 100mA nominal, normal; 5mA, sleep
Display: Six-digit LED direct readout of platter speed in rpm
Resolution: 0.001rpm
Frequency stability: Crystal-controlled +/-2.5ppm (+/-0.00025%)
Option: Direct connection to Eagle PSU provides digital synchronization of platter speed to +/-0.005rpm
Dimensions: 2.50″ x 1.1875″ x 3.565″
Weight: 4 oz.
Price: $235

Eagle
Type: Turntable power supply/speed controller
Case: One-piece extruded aluminum
Operating modes: Standby, sleep, normal, voltage calibration, frequency calibration
Power requirements: DC supply 24VDC 800mA nominal, normal mode; 20mA, standby; 5mA, sleep
Output voltage: 115/230V RMS nominal, adjustable from 85 to 115VAC and 170 to 230VAC
Distortion: Less than 0.04% (DDS output)
Speed adjust: +/-1.0rpm in 0.1rpm steps in normal mode; +/-1.0rpm in 0.01rpm steps in calibration mode
Min freq step: 35µHz
Freq stability: Crystal-controlled ±100ppm
Freq accuracy: +/-0.01%
Controller dimensions: 2.50″ x 1.1875″ x 3.565″
Amp dimensions: 4″ x 2″ x 6″
Weight: Controller, 4 oz.; amp, 2 lbs.
Price: $525

PHOENIX ENGINEERING, LLC.
449 Terrace Lake Ct.
Green Bay, WI 54311
(920) 468-3296
[email protected]

Andre Jennings

By Andre Jennings

My professional career has spanned 30+ years in electronics engineering. Some of the interesting products I’ve been involved with include Cellular Digital Packet Data modems, automotive ignition-interlock systems, military force protection/communications systems, and thrust-vector controls for space launch vehicles.

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