OLID-STATE 3-CHANNEL COLOR ORGAN
By DONALD LANCASTER
Construction of a well-designed display device that produces changes in the color intensity and hue in step with musical signals_ Can be connected to hi-fi amplifier and will handle 1 kw_ of light power.
40" . 30. S",
and a "too electronic looking design" have dis(,'Ouraged popu lar acceptancc. It is felt thai the present design overcomes some of these objections. The color organ to be described consists of two units, a control box the size of several books, and its associated display, the size of a bookshelf. The former is capable of handling up to 360 watts per channel of regular nO-volt light bulbs, parallel connected, giving a total power capa bility of around one kilowatt. The control box operates off the loudspcnker terminals of any music system and consumes less than one watt of audio power. Efficiency is over 9i at full output, and control-box heating is negligible. Power "on-off," red drive, blue drive, and green drive are the only controls necessary. The ovcr-all level is adjusted to meet average listening requiremcnts by changing taps inside the unit; once set on a given music system, adjustment is un necessary. The filters that separate the music into its com poncnts arc adjustable to select the portions of the audio spec trum and to compel1Snte for the nature and quality of the progmm materinl. Fig. 1 is a block diagram of the system. It is first neeFig. I. Simplified block dio9.om of the tolo. 0'90" d.... ibed.
organ may be broadly defined as any de vice that somehow relates a lighted display to an associated musical background. This is usually done in such a way that various colors correspond in some manner to certain frc(Jucncics ill the musical selection. A color organ typically consists of three filters separat ing the high-, mid-range-, and low-frequency component of the music, followed by circ\litry allowing the control of the three primary light mlars in a suitable display. In the past, color organs have been either 100 hlrge or too small in scope or pel'fonnal1c:c for average home hi,fi lise; aiso, high cosl
essary to divide the audio spectrum with the r;!ter system. This is accomplished by a high-pass, bandpass, and lo\\, pass filter network. Adjustable LC filters were chosen for thcir availability. their uniformity, and their steep slopes beyond cut-off. Next, it is dcsirable to deri\'e a d.c. control voltage from the filter output. A drive control at this point adjusts the maximum value of a given filter output. This is followed by a rectifler and filter network. The actual illumination level is controlled by varying the duty cycle of the a.c. wave impressed on the load. This is shown ill Fig. 2A. For L'Onvenience, alternate cycles arc im'crted by means of the full-wave rectifier to insure only positive or zero valucs of voltage. This docs not affect load power. A silicon-controlled reetifler (Sen) in series with each lamp load behaves as a simple switch, turning on when its gate is pulsed and remaining on for the rest of the cycle. The scn turns off as its anode voltage approaches zero.
CO. BRILLIANCE "IGI< 91llLLIANCE
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