McIntoshMI-3usedMcIntosh MI-3 Tuner Maximum Performance Indicator**Please click here to check out our newly launched SkyFi Audio website with additional items for sale** If you have a McIntosh vintage tuner then this accessory is an absolute must!The built in os...1999.00

McIntosh MI-3 Tuner Maximum Performance Indicator

Listing ID: lisa0b77 Classified 
 Listed  · 440 Views
Time Left: 15 Days


Buy It Now
Payment methodsPaypal card

Contact seller after sale to pay via Certified check, Personal check or Wire Transfer

Ships fromGlen Rock, NJ, 07452
Ships toUnited States
Package dimensionsunspecified
Shipping carrierUPS
Shipping cost$79.00
Agon miniAverage Research Pricing

**Please click here to check out our newly launched SkyFi Audio website with additional items for sale**

If you have a McIntosh vintage tuner then this accessory is an absolute must!

The built in oscilloscope illustrates the performance of the signal, which also happens to be incredibly entertaining to watch!

This example is the cleanest we have ever seen, and also very rare.  These are usually found with a faded 3" CRT display tube, or damaged glass which is no longer available from McIntosh (or anywhere).

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

*Note this MI-3 is actually tube powered - VS the later model solid state MPI-4.

More Information from the McIntosh Owner's Manual:

The Mclntosh Ml 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 Mclntosh Ml 3 Maximum Performance Indicator makes it easy for you to attain professional broadcasting quality FM listening.

The Mclntosh Ml 3 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 Ml 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 Ml 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 Ml 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 Ml 3 picture tube display.

The Ml 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 tuning occurs when the display trace is centered hori- zontally on the screen. Since the display trace effectively follows the tuner I.F. response curve, centering the trace tunes the de- tector to the center of the I.F. curve.

The Ml 3 Maximum Performance Indicator is a versatile instrument.

When used with either a stereo preamplifier, or power amplifier the Ml 3 when switched to the L+R AUDIO position will show you the character of the audio signals present. The Ml 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 de- livered.
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 bal- ance control you can change the angle of the L+R or L — R display.
6.  A stereo program will be a 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.

MI3 Specifications:

Signal Strength (vertical) Input:
— 700 MV
Left Audio (vertical) Input:
20 MV
Deviation (horizontal) Input:
±350 MV
Right Audio (horizontal) Input:
20 MV

Front panel: 
16 inches wide by 5-7/16 inches high

Chassis (including PANLOC shelf):
15 inches wide by 5 inches high by 13 inches deep, including connectors

Clearance in front of mounting panel, including knobs:
1-1⁄2 inches

1— 3RP1, 3 inch cathode ray tube
4— 6EA8, horizontal and vertical deflection amplifiers
1— 6EA8, electronic voltage regulator
2— OB2, voltage regulators
1— Selenium rectifier, high voltage rectifier
6— Selenium rectifiers, low-voltage supply
4— Silicon planar transistors

Chassis only, 23 pounds
In shipping carton, 30 pounds

Anodized gold and black glass front panel

50 watts, 105 to 125 volts
50 to 60 cycles

1 Ampere Slo-Blo

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

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

Thanks for looking and please click here if you would like to receive a list of the equipment we receive from time to time.  We promise not to bombard you with junk email.



This item will be professionally packaged and insured for safe transit to your home. 

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

If we don’t have the original manufacture's packaging, we use heavy duty double ply corrugated boxes with Instapak expanding foam custom inserts.  In many cases this has proven to be better than the original packaging.  We also use high quality fiber reinforced tape to seal our packages.  Lightweight items will be bubble wrapped and shipped in a high-quality box. 

This item is available for pickup in Glen Rock with convenient parking near our building.

NJ Residents or anyone picking up without a resale certificate will need to pay NJ Sales Tax.

Use the Buy It Now button and we will cover the PayPal fees.

Thanks for looking and be sure to call us at 201-879-0000 with any questions. 

Please also click here to visit our Audiogon store to see the rest of the items we have for sale.



SkyFi Audio is a small startup business specializing in the purchase, reconditioning, and reselling of select high-end audio equipment.  We only buy equipment the we admire and are passionate about. No mid-fi, no gimmicks, no junk. 

Each piece of equipment is cosmetically restored and fully tested in our well-equipped lab by an engineer with 30+ years of experience in the HiFi world. If it does not meet or exceed the original manufactures specifications, it will not be sold.  We are very selective about the equipment we purchase, focusing on mostly analog, high-build quality, American, and European built units.

Through our sister company, which is an authorized dealer for McIntosh, Audio Research, Sonus Faber, ClearAudio, Pro-Ject Audio Systems, and Sony ES, we have access to OEM parts, service, and support.  If you are local and looking for new equipment from the above-mentioned manufacturers, please drop us a line as we can arrange both sales and professional installation in the tri-state area.


We do not accept or review any offers that do not go through the official Audiogon system. We have too many items for sale and it’s nearly impossible to keep track of offers outside of the official system. Please don’t message, email, or text any offers. 

If you do not see a “Make an Offer” button, it means we are not considering any offers on that item.   


We prefer working through PayPal which allows you to use a credit card or bank transfer. We do not charge extra for any payment fees if you purchase the item at the asking price.  You can also send us a personal check (which will need to clear before shipping), certified check, money order, or wire transfer. International clients without access to PayPal should use a bank wire transfer. 

If you are picking up an item we do not accept PayPal.  You must pay in person with cash, certified or bank check, or wire transfer.  If you make a PayPal payment and are picking up the item, it will be returned. 


We accept trade-ins of equal or lesser value under certain conditions.  Simply ask and let us know the exact model, condition, and the accessories that are included (such as the original box, remote, cables, manual, etc.).  We will only consider high-end equipment from mainstream manufacturers such as McIntosh, Mark Levinson, Audio Research, Krell, etc. and will typically pass on displays, projectors, receivers, dated surround processors, and mid-fi equipment of any type.  We will offer a fair value for your equipment, but keep in mind we are running a business and will need to be able to resell the equipment at a profit after investing a great deal of time and resources in testing, certifying, repairing, cleaning, and packaging the incoming equipment.  If you are looking for top dollar we suggest attempting to sell it directly to an end user on your own.

SELL US YOUR GEAR (Working or Broken)

We will also purchase your used or broken gear and arrange pickup if you are in our local market. Just drop us a note for a quote but be sure to include the condition and what is included. 

HOW TO VISIT US                                                                                                        

We are currently operating from our shop located in Glen Rock, NJ.  You are welcome to make an appointment if there is a piece of equipment you would like to see in operation before or after purchase.  We have a well-equipped, dedicated listening room with tons of equipment of all makes and models.  We are not a store, so please don’t make an appointment if you are just curious as to how a speaker or piece of equipment sounds.  In essence, no tire kickers please.

You can call 201-879-0000 with any questions or to schedule an appointment.  We can also arrange to install, calibrate, and tune the gear in your listening room if you’re local to our area.  This is super useful when purchasing large speakers or heavy amplifiers.  It’s also great for ensuring your new turntable is setup correctly in its final resting place.  


No questions have been asked about this item.

Ask the seller a public question

You must log in to ask a question.

Return Policy
Return Window

Returns are not accepted on this item.


member since December 2000

SkyFi Audio  Verified Dealer

Last 12 months

2 Watchers