The Consumer Electronics Hall of Fame: McIntosh MR 78 Tuner
- Thread starter Capt.Willard
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After they told him he was nuts?
Only joking—great reply thanks.
If that were the case nearly all engineers would be out of work!
Gregory
Soundco Kid
Printed inside the front cover of the MR 77 Owner's Manual – RIMO filter code – from IBM punched card input.
https://en.wikipedia.org/wiki/Punched_card
-Greg
https://en.wikipedia.org/wiki/Punched_card
-Greg
Gregory
Soundco Kid
Yep, I'm out of work and away from Gov. Fortunately there's AK.If that were the case nearly all engineers would be out of work!
Gregory
Soundco Kid
Yes, we were both working on the same topic.
I remember seeing these TUNERS and MPI-4 on the shelf at Soundco, Roosevelt Ave in the summer of 1974, playing with the scope and seeing my reflection in the glass of the MR 77 in the darkened sound room.
- MR 77: sold from 1970-1978, last retail 699
- MR 78: sold from 1972-1979, last retail 1699
- MPI–4: sold from 1973-1977, last retail 599
Let's make it Sept 1974—just starting Jr year in HS.
-Greg
KentTeffeteller
Gimpus Stereophilus!
MR 74 better than the MR 78 or the MR 80. MR 74 had each stage designed by the McIntosh engineer who did that stage best. MR 74 not as selective, but far better sonics.
Gregory
Soundco Kid
See this thread:
https://audiokarma.org/forums/index.php?threads/mr74-vs-mr77.625188/
This AC webpage says Modafferi can update ANY Mc tuner or any age.
https://www.audioclassics.com/mods
-Greg
KentTeffeteller
Gimpus Stereophilus!
MR 74 is also more repairable, the MR 75 and 77 have aged less well.
I've had/heard a lot of tuners in my 40+ years of audio experiences, including a few Mc's, although not a 74. But I must say after spending some time now with a recently purchased 78, I'm satisfied that it's easily one of the best I've ever heard. I can pick up my priority small college stations that are 35(500) and 45(250 watts) miles away, and a very small community station(160 watts) that is 23 miles away. All very clearly, with a rooftop antenna.
I would love to hear the 74 one day, but for now this one will do fine.
I would love to hear the 74 one day, but for now this one will do fine.
Gregory
Soundco Kid
Only a few AK'ers have posted describing use of their Mc tuners as they were designed by McIntosh to be used. This guy is one of them. Hey SB, can you describe your antenna system?
An antenna is the input device to your tuner, just as a tuner is for your preamp. One positions and points their speakers in the room for best results, likewise one positions and points their FM antenna for best results.
-Greg
The antenna is a standard, old non directional rooftop type that was on top of the house when I bought it in 1998. In other words nothing terribly special or unique, but it does the job. I would think that if I upgraded to a modern, directional version I would probably improve my signal some, but as I indicated the 78 does a great job of pulling in the stations I care about so I'd rather spend the money on records
I use a rooftop Magnum Dynalab ST-2 omnidirectional which works reasonably well but a directional rotatable antenna is the ultimate. Location to desired station dictates how good an antenna is needed however. I've gotten much better reception with nothing more than a freebie dipole wire antenna than with the antenna system I have now at my present location.
I'm surprised that we're 3 pages in and there's been no mention of a Modeferri modded MR78. For the longest time that seemed to be the thing to do with these units.
What is the general consensus on improved SQ as well as it's impact on desirability and value?
What is the general consensus on improved SQ as well as it's impact on desirability and value?
Gregory
Soundco Kid
What is SQ? sales, selling quality?
Was looking at that AC webpage the other day: https://www.audioclassics.com/mods
Modafferi Mod
- B- power supply - improved regulation, less hum.
- RF selectivity improved for better spurious rejection.
- IF regeneration fixed - better weak signal reception.
- IF 'tailbiting' fixed - this eliminates degraded reception at 96.3 and 107.0 MHz from ninth and tenth IF harmonics.
- Stereo decoder slew-rate optimized by modifying op-amp feedback circuits; reduces distortion, improves separation.
- Diode D307 installed (this was left out of MR78 but was used in MR77); this reduces 'klunk' noises on fixed output jacks when tuner is turned on and off.
- IF phase trimming - 'gimmick' capacitors added as needed in NORMAL IF filter for improved stereo separation.
- RF oscillator emitter tap re-dressed for minimum leakage inductance; reduces drift and eliminates oscillator pulling on strong signals.
- Jung-Marsh capacitor upgrade in MPX and audio circuits.
- Cardas audio output, Midas scope output jacks installed.
- Muting ground changed - improved muting performance.
- 19 kHz stereo pilot circuit change, reduces stereo distortion.
- Buffer resistor installed in pointer lamp circuit, prevents lamp heat from burning red light filter material.
AC charges a grand (1,000 bucks) for those mods.
https://audiokarma.org/forums/index.php?threads/modafierri-mod-mr67-mr71-is-it-worth-it.16304/
-Greg
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Gregory
Soundco Kid
The ST-2 is a quarter-wave monopole with no ground plane radials. A quarter-wave element is narrow band, so a loading coil is used at the base for 88-108 MHz coverage.
Since FM is transmitted in CP (circular polarization) it doesn't matter if you have vertical or horizontal elements, except for the directivity pattern. H vs V antennas simply have different patterns and gains.
The ST-2 will have an omni pattern similar to the one below, with nulls at zenith and straight down.
I used a basic Channel Master turnstile antenna as an omni reference in the MR80 Chicago FM experiment. They're usually two folded dipoles strapped close together, like the wire folded dipole that comes with your radio or tuner.
You could stack a pair of turnstiles for higher gain (tighter elevation pattern).
I went nuts and installed stacked Stereo Probe 9 antennas, but moved away before the experiment was complete. A Yagi antenna has a `beam´ in the optical sense, so it's like pointing a `beam´ at the FM transmission tower (think optics), think of an antenna as if it was a light source, transmit and receive having reciprocity.
http://www.antenna-theory.com/definitions/reciprocity.php
Everyone talks about their speaker patterns, speaker position, and speaker pointing (tilt back, toe in, corner, etc), but not so much with FM antennas, which are MUCH less expensive than speakers!
Ex: a corner reflector antenna is similar to placing a speaker in the corner, directivity wise. There are horn antennas similar in concept to horn speakers.
-Greg
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Sorry, SQ is sound quality. Thanks for the info.
I would have no interest in this mod. It would be overkill for a component that gets used to listen to small stations that are not terribly high quality to begin with. Plus I mostly use it to listen to music that is not even close to audiophile grade(maybe some of the classical stuff, but again, small, compressed station). My system is humble anyway, so even if the stations were delivery the highest quality signals and sound, I doubt I'd hear much of a difference.
A lot of rabbit holes to fall into with this hobby.
Desirability and value definitely higher, usually translating to ~ $500 premium for units so modded from what I observed on the auction site.
I cannot comment on SQ benefits.
chuckworkb
Super Member
Typo in the article - MR 78 was a trailblazer, the first AM/FM tuner precise enough to tune in the weaker of two radio signals broadcast on very close frequencies.
There is no AM on the MR78. It is a fantasic FM tuner that is for sure. I mostly listen to classical stations on Sunday mornings, and there are a few good university radio stations still out there I listen to.
There is no AM on the MR78. It is a fantasic FM tuner that is for sure. I mostly listen to classical stations on Sunday mornings, and there are a few good university radio stations still out there I listen to.