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McIntosh MI-3 Tuner Maximum Performance Indicator

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Pickup currently unavailable at SkyFi 479

Mcintosh Mi-3 Tuner Maximum Performance Indicator

McIntosh MI-3 Tuner Maximum Performance Indicator

SkyFi 479

Pickup currently unavailable

479 South Broad Street
Glen Rock NJ 07452
United States


A unique vintage piece from McIntosh and a great match for your vintage tuner. 

Plus it looks super cool dancing in action and we're betting your friends have never seen anything like it.

In good cosmetic condition and very good working condition.

The display tube is super bright and responsive, the glass is free from cracks, and the cabinet work is rust free with great paint quality.

The cabinet has some scratches and a small piece of wood in the upper-right hand corner missing, but it's otherwise very presentable for being 49 years old (50 in 2020!).

*Note this MI-3 was tube powered, vs the later model MPI-4 which was solid state.

More Info (courtesy of

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.

It shows you what you need to do to improve your system's overall performance. It is designed to be used with an FM tuner and stereo preamplifier.

When the MI-3 is used with an FM tuner 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 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 shown as horizontal deflection. Multipath reception appears as a peak or valley in the MI 3 picture tube display.

Signal strength (vertical) input:  700mV
Dimensions:  16 x 5-7/6 x 13 inches
Weight:  23 lbs
Finish:  Anodized gold and black gloss front panel
Year:  1970

Click here for a PDF copy of the original MI-3 Owner's Manual

Click here for a PDF copy of the original MI-3 Service Manual

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.



Original Box








Physical Condition


Working Condition


SKU: McIntosh MI-3