The Orban Stereo Synthesizer processes any monophonic sound source into pseudostereo quickly and easily. The pseudo-stereo does not degrade the quality of the mono recording, and possesses many attributes of true stereo, such as depth, space, directionality, stability, and good channel balance. The synthetic stereo is created by a complementary comb filter derived by a patented phase-cancellation technique. The incoming spectrum is divided into five bands of about two octaves each. Bands are alternately placed in the left and right channels, producing a convincing stereo illusion. The two DIMENSION controls vary the relative positioning of the bands. This facilitates achieving good subjective channel balance regardless of the average spectral balance of the program. There is a "best compromise" DIMENSION setting (LGW=3.0; HIGH=7.5) which works well for average program material. This setting may be used if it is impractical to readjust the DIMENSION controls for each new piece of program material. If you wish to set the DIMENSION controls permanently (so that they cannot be accidentally misadjusted), fixed resistors or Beckman Industrial 72PR25K trimmers can be installed in holes provided in the circuit board. A STEREO/MONO switch provides quick comparison between the original mono input and the stereo-synthesized output. A SEPARATION control allows reduction of the stereo separation by partially mixing the channels. This may be useful to permit more natural headphone listening, to reduce the vertical cutter excursion in disk cutting, and to increase mono loudness in FM stereo broadcast ing. A GAIN control is located between the active-balanced input stage and the signal processing circuitry. Thus it cannot prevent overload of the input stage due to excessive drive levels. Up to 9dB of gain is available. Mono compatibility is assured by the following facts: I. The electrical sum of the two output channels is proportional to the mono input to the Synthesizer Thus, a listener can recover the original mono by summing the two stereo channels together. This removes many "purist" objections to pseudo-stereo, since the purist can choose freely between pseudo-stereo and the original mono. It also means that mono FM listeners will hear the original mono source when listening in mono to a stereo FM station, and that the lateral modulation of a stereo disk will represent the original mono signal. 2. The sum of the left and right powers (as a function of frequency) is proportional to the power in the mono input. Thus, the acoustical frequency balance of the pseudo-stereo is identical to the frequency balance of the mono: coloration is not introduced by the synthesis process. Both (I) and (2) hold for ony adjustments of the Stereo Synthesizer operating controls. The output of the Stereo Synthesizer can drive any device requiring standard line levels and impedances. If gain balance is carefully maintained after the Stereo Synthesizer then the following relationships will hold accurately: 1. If the Stereo Synthesizer output is recorded on tape and is later played back on a machine having substantial time delay or phase shift between the two channels, the "phasing" sound in the mono sum signal will be greatly reduced. 2. In disk cutting, the lateral cut will represent the original mono input of the Stereo Synthesizer On playback, if the channels of the stereo pickip are paralleled, the output will represent the original mono source. 3. In FM stereo broadcasting, mono listeners will hear the original mono signal. The input is active-balanced, bridging. The outputs are supplied unbalanced, but can be balanced by installation of a retrofit kit available from your Orban dealer or directly from Orban The kit consists of hardware and two specially-designed transformers. Holes are provided in the chassis for quick field installation. If the "+" input is driven positive, the output will also be driven positive. That is, the device is non-inverting ("in-phase") from input to output.