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Old 15th March 2010, 02:33 AM   #1
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Default Pleas help identify this McIntosh valve amplifier

In short, I got this from a friend. It looks like commercial product that uses two massive (OEM?) McIntosh amplifiers. It's really heavy

The tubes are 12AU7, 12AX7, 12BH7, 12AT7 and two KT88. The input is BNC and the print next to the potentiometer (with switch) reads "2.0V setting for McIntosh preamp. There is a speaker output-strip with labels "GND,COM,4,8,16". There is also an output-socket that seems to be feeding some higher-impedance loads.

I can make more pics tomorrow. Can anyone identify this beast?
Could the amplifiers be operated @ 240VAC 50Hz with a sufficiently large step-down transformer or would the 50Hz cause trouble (less efficiency)?
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Old 15th March 2010, 02:43 AM   #2
Glowbug is offline Glowbug  United States
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Looks like some kind of lab-grade signal generator...maybe you could remove the frequency-determining part of it and run them full range
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Old 15th March 2010, 02:53 AM   #3
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Looks like a pair of MC 75 monoblocks.

Click the image to open in full size.
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Old 15th March 2010, 02:54 AM   #4
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You lucky dog!! They are in fact McIntosh MC75s The output and power transformer numbers clinch it. I'm sure because they are the same as mine.
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Old 15th March 2010, 02:57 AM   #5
Glowbug is offline Glowbug  United States
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Rodeo, do you have a better photo of the faceplate?
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Old 15th March 2010, 03:00 AM   #6
munorc is offline munorc  United States
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I do not think it was uncommon for them to be used for non-audio applications. The one I showed above was from a collection we had in a University engineering department. They were used, in our case, as small shaker amplifiers for vibrations testing.

Click the image to open in full size.

(An MC 40, 60, 75 and 275, not in the order pictured)
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Old 15th March 2010, 03:02 AM   #7
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Here you go.
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Old 15th March 2010, 03:09 AM   #8
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I'll venture a guess and say that's some sort of instrumentation, with a pair of MC75 based amps in it. The MC75 schematic is here.

McIntosh did not skimp on "iron". I don't think you need worry about 50 Hz. mains. Buy a pair of Allied 6K175VCP or equivalent 2000 VA step down autoformers. "Mac" circuitry is Class "B" and you don't want adverse regulation effects in the autoformer. Thank Kevin K. for that tip.

The "iron" in your possession is GOLDEN. Do a full stem to stern refurb with modern parts. Then play those monoblocks regularly. You will be smiling.

That's quite a find and I'm jealous.
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Old 15th March 2010, 03:12 AM   #9
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This is from the estate of the late husband of a friend's kindergarten nanny who called him up to clear his garage after 40 years of hoarding...we spent the whole day there assessing the vast of his collection. Mind boggling. We'll be back in two week with a van. I remember a 1.5kVA step-down transformer that'd go nicely with the twins...
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Old 15th March 2010, 03:30 AM   #10
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Would you guys use WD-40 to clean the amp?
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