manual - Furman Sound

AR-20 II Voltage Regulator / power conditionerunit’s 20 amp capacity is exceeded at anytime.2. A fast-blow 1/4 amp fuse is located insidethe unit. This fuse will blow if the unit hasbeen connected to a voltage that is abovethe range of the Extreme Voltage Shutdowncircuitry. To replace it, the unit mustbe completely disconnected from all powerand removed from its rack. The six hex headscrews and two Phillips head screws holdingthe top cover must be removed. The internalfuse is located in a holder on the printed circuitboard. Replace the fuse only with the exactsame type (1/4 fast blow).Input Voltage & CurrentMonitoringThe digital meter at the left of the front panelmake up a meter that indicates INPUT VOLT-AGE or CURRENT levels. A switch to the leftof the meter allows the user to switch betweenthese two readings. It is important to rememberthat this is the voltage or current coming fromthe wall before it has been regulated. This isNOT the level of voltage going into the equipmentyou have connected to the AR-20 II.Output Voltage MonitoringA green LED labelled OUTPUT IN REGULATIONindicates proper function (i.e., that the output voltageis within ±5V of the selected output voltage).Your equipment will always work normally whenthis light is on, and often will work satisfactorilyeven when it is off.The AR-20 II offers a digital voltage meter tomonitor the incoming line (the Voltage Regulatoroutput).InstallationBecause of their toroidal transformer design,Furman Voltage Regulators may be positionednear most other equipment without fearthat the other equipment will be disrupted byleakage of a strong 50/60 Hz magnetic field.Nevertheless, suggested rack locations wouldbe either at the top or bottom.As with any rackmount equipment, be sure touse 10-32 machine screws for mounting in therack’s tapped holes (this is not a metric size).In particular, beware of 10-24 screws, whichmay fit if forced but which will strip the threads.To avoid marring the front panel finish, useplastic washers under the screw heads.DesignThe AR-Series uses a design based on aneight-tap toroidal autoformer. The toroidal designassures minimal leakage of stray magneticfields, and, because of its high efficiency, a verycompact size for its rating. The Voltage Regulator’scircuitry monitors the incoming line voltagewith each cycle, comparing it to an extremelyprecise voltage reference, accurate to ±0.15%.If a voltage fluctuation requires that a differenttap be selected, the new tap is electronicallyswitched exactly at the zero-crossing, to avoiddistorting the AC waveform. If necessary, it canswitch taps as often as once each cycle. Mostcommercial voltage regulators using multipletappedtransformers switch taps at uncontrolledtimes, thereby creating voltage spikes andclicks that can leak into the audio! Hysteresis inthe switching circuits avoids “chatter” or unnecessaryswitching back and forth between adjacenttaps. Unlike those voltage regulators thatemploy ferro-resonant transformers, Furman4