Page 1
DO NOT attempt to open this equipment unless you are qualified to do so, have the neces- sary test equipment and are operating the Circle 5a from an ISOLATED POWER SUPPLY. Ensure that only the correct mains voltage is applied, as marked on the module.
Page 3
Contents Page 1: The cover and warning Page 2: Section 1.0 External arrangement and comments on connectors/controls Page 3: General arrangement, notes on testing Page 4: Opening the Circle5A Page 5: Circuit diagram: active filters Page 6: Circuit diagram: power stage Page 7: Circuit diagram: mains input Page 8: PCB silk screen, top view Page 9: Parts list...
Page 4
1.0 Externals This is a view of the external controls on the Circle5A. The function of the Master Volume control is to scale down excessive input signals. In a set-up where the signal level is scaled so that set to maximum (fully clockwide) an input of 0.775vdBv, on the loudest peaks, will fully drive the power amplifiers.
Page 5
Removing the Circle 5a active module from the cabinet It is absoluletely essential that before removing 1. A 3.0mm cross head screwdriver of the the module you have the necessary tools, a clear space, and sufficient uninterrupted time to work. Rushing leades to mistakes, and mis- tekes can be dangerous and impair the excel- lent performance of your Circle 5a speakers.
Page 6
2.0 General arrangement NOTE CAREFULLY: DO NOT CONNECT EITHER OF THE BASS All the signal processing circuitry of the OUTPUT TERMINALS TO GROUND SINCE Circle5A amplifier module is contained on one THIS WILL INSTANTANEOUSLY DESTROY double-sided plated-through PCB. There are no ONE OR BOTH BASS POWER IC’S.
Page 7
inside Photograph of the amp module viewed from the Version 1d: 01.99 Page 7...
Page 8
Mute-relay modification A modification involving improving the switch on/off threshold of the mute relay was introduced shortly after production commenced. This involves the changing of resistor R46, initially fitted as 100kR to 200k or 220kR. It is not practical or necessary to remove the PCB, and the fitted resistor can be cut out, and a substitute resistor carefully soldered in it’s place.
Page 9
Be sure to return the preset adjuster to the analysis equipment is available. original level or to make a note on the outside of the module that the Circle 5a is no longer As despatched, the tweeter control is normal- standard.