McIntosh MI-3 Maximum Performance Indicator. McIntosh audio scope. Unit looks very nice. There is some small bubbling in the glass faceplate mainly around the edge as shown in the images. The scope has a bright display and works very well. Great for monitoring audio signal and multi-path adjustment for tunes. The unit has mostly McIntosh tubes inside which look to be original. Buyer pays $50 shipping in CONUS

Up for sale is a very rare in very good condition Mcintosh MI 3 Maximum Performance Indicator with manual. Buyer to pay $200.00 Shipping within the 48 Continental United States. Payment due at time of purchase. The built in oscilloscope illustrates the performance of the signal, which also happens to be entertaining to watch! More information from the McIntosh Owners Manual: The McIntosh MI 3 is five laboratory instruments combined into one compact instrument. It is a professional oscilloscope, relative signal strength indicator, calibrated FM deviation meter, calibrated balance meter, and phase indicator. These instruments are used by FM stations to determine the best possible performance for your listening enjoyment. The McIntosh MI 3 Maximum Performance Indicator makes it easy for you to attain professional broadcasting quality FM listening. The McIntosh MI 3 shows you what you need to do to improve your systems overall performance. It is designed to be used with an FM tuner and stereo preamplifier. When the MI 3 is used with an FM turner it will detect and display multipath reception. Multipath reception is the result of a reflected signal arriving at the tuner antenna slightly later than the direct signal. By rotating or repositioning your FM antenna it is possible to reduce the multipath reception. The MI 3 Maximum Performance Indicator makes it easy to know when the FM antenna is oriented for the best reception of any station. To show multipath reception the MI 3 displays instantaneous signal strength versus frequency deviation. Signal strength is shown as vertical deflection of the indicator display beam. Frequency deviation is show as horizontal deflection. Multipath reception appears as a peak or valley in the MI 3 picture tube display. The MI 3 is a very effective tuning indicator: 1. Signal strength is shown by the vertical position of the display trace. The higher the position of the trace the greater the signal strength. 2. Correct turning occurs when the display trace is centered horizontally on the screen. Since the display trace effectively follows the turner I.F. response curve, centering the trace tunes the detector to the center of the I.F. curve. The MI 3 Maximum Performance Indicator is a versatile instrument. When used with either a stereo preamplifier, or power amplifier the MI 3 when switched to the L + R AUDIO position will show you the character of the audio signals present. The MI 3 will: 1. Display a trace along the L+R line when a monaural program is playing. 2. Will display along the L-R line when a monaural program source has one channel out of phase. 3. Display a vertical trace if only the left channel is being delivered. 4. Display a horizontal trace when only the right channel is being delivered. 5. Helps you set the precise balance of your system. With the balance control you can change the angle of the L+R or L-R display. 6. A stereo program will be complex and varying circular or elliptical display of irregular outline that depends on channel separation or on the phase amplitude relation of the left and right channel.