TurntablePSU.comReviews and Technical Analysis
Pink Triangle Too PSU
Overview
The Pink Triangle Too PSU is a dual frequency dual phase supply that uses 2 fixed frequency crystals to generate the 33/45 RPM sinewave signal. The clock source for 33 RPM is a 3.2768 MHz Crystal (50 Hz). The clock source for 45 RPM is a 4.433618 MHz crystal (67.5 Hz). All crystals have a frequency stability of .01% (100 PPM). A front panel rotary switch is used for changing between 33 and 45 RPM.
The Too PSU is powered by a 120 or 240 VAC input, and the PSU has one output (DIN 5 pin) to the turntable. Like most of the other PSUs on the market, the Too PSU uses 50Hz for 33 RPM and 67.5Hz for 45 RPM, so the turntable belt must be installed on the small spindle of the pulley (33 RPM). The manual advises the user to start in 33 RPM mode and switch to 45 RPM rather than starting in 45 RPM mode. There is no tempo or calibration adjustment for either speed.
Circuit Description
The selected crystal is divided down by a 16 bit digital counter for a total divide ratio of 65536. The crystal frequency used for 33 RPM divides down cleanly to 50Hz, but the crystal used for 45 RPM does not divide to exactly 67.5. A standard value crystal is used and the output frequency is 67.65 Hz. The output of the divider is a square wave so this must be filtered by a 2 stage opamp integrator low pass filter. The output of the 2nd integrator drives a buffer for the sinewave output and a phase shifter for the cosine output. Each output drives one half of a TDA2004 stereo amplifier. The output of each amplifier channel drives a step up transformer to bring the voltage to 115VAC to drive the motor.
Measurements
The output frequency at 33.3 RPM measured 50.00 Hz and 67.65 Hz at 45 RPM.
Specifications
Nominal Speeds............................33 and 45 RPM
Speed Stability..............................0.01% (100 PPM)
Distortion (Freq Generator).............1.25%
Distortion (115VAC output)...............2.65%
Pitch Control.................................Not adjustable
Output Power................................3W
Reduced Voltage...........................Not available
Turntable Connection.....................DIN 5 pin connector
Weight..........................................8 Oz.