• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

McIntosh Goodness From Scratch

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Here we go again! A MAC is no big deal to build from scratch, IF you have a source for their rather unique output transformers. I know of nobody except for Plitron that makes any type of output transformer that even closely resembles the old McIntosh "unity coupled" output transformers. And Plitron only has one transformer in their inventory that is like the old MAC units. It would be better suited for making a MC-40 /MC-240 clone, not a MC-75 / MC-275 IIRC.
Do a search on this forum for "McIntosh Output Transformer" or "Unity Coupled Transformer". This has been written about here a lot in the past.
And one more thing... If you decide to do this project, make a MC-40 clone instead. They are good for an actual 60 watts RMS (McIntosh are severely under-rated in their specs) and are probably the best sounding of all the old common MAC tube amps (MC-30, MC-40, MC-60, MC-75).
You can occasionally find old MAC outputs on Ebay, from NOS to old rusty bad units. Good ones go for $200-$350 each depending on what model.
Glad to hear the hum is solved.

Has anybody built something like a McIntosh MC-275 from scratch? Why not?

This question could surely start in interesting discussion on the philosophy of cloning a classic.

When do you stop calling a clone that is not an exact duplicate with original parts by its given model name? Is it a Mac 275 if the power tranny is not the original? Will it ''sound'' the same? Does the builder care, if it sounds the same? A different OPT set? Not the same brand of coupling caps? Not the same driver tubes? Not the same finals? Not the same chassis?

When does an '69 Impala stop being an Impala? You like the body but you think a Ford power train is ''better.'' So you slap in a new motor/tranny/differential Bigger wheels and lower the roof but you still call it a '69 Impala. It won't ''sound'' the same.

Have fun with that game. Everyone has to play it. The winner is normally disputed.
Well, it looks like this sort of project is WAY, WAY beyond my capabilities. My next project will be my first, and I barely understand volts, amps and watts.

But you know.....I am just ignorant enough to question all this scary talk about "don't try this at home." Let's take an example I am vaguely familiar with regarding automobiles. In the late fifties Porsche made a 2-liter, four-cylinder, four-cam (sixteen valve) engine the size of a suitcase that could spin 8000 rpm and make 200 hp. Amazing. They say it takes an expert about eight hours to adjust the valve lash. This is because the cams are not driven by belts or chains, but rather are gear-driven. So.....adjusting them is an interative process of measuring - adjusting - measuring - adjusting - measuring - adjusting......and more measuring and adjusting. The point is that potentially, virtually anyone with basic mechanical skills and a few specific tools could do it, as long as they study and understand the steps.

Again, I am ignorant of electronics stuff. Not dismissive, just ignorant. I just don't understand why an expert could not make a parts list and lay out a build procedure, including whatever testing and adjusting must be performed, that could be followed by anyone with access to the proper tools and equipment.
FWIW, I don't care one whit about originality for originality's sake. My goal is the sound. I have heard early McIntosh tube stuff, and the sound is jaw-dropping. That is my goal. The jaw drop.

I'll use the car analogy presented by 20to20, but with a different make and model. I own a 1978 Porsche 911SC coupe. It is a lovely car in a very dark, dark, dark opaque (non-metallic) chocolate brown. It has lovely curves, not unlike a woman. But you know.....I don't care what it looks like. I kinda wish it looked like a Yugo. I don't revel in the stares I get while driving it. This is not a piece of jewelry. It is a CAR. My sole interest in this car is performance-related. It is like a go-cart coupe with license plates. I have it down to just under 2400 lbs now, with solid suspension bushings, blah blah blah. In a word, this car is the most "obedient" I have ever driven. Stops on a dime, corners like it's on rails, etc. She's a dancer.

This is what I am going toward in this, my latest obsession. Tube sound. I am in the construction industry, and if I can draw a chassis, I can get it fabbed from stainless for almost nothing. Chassis is not a problem. So......if I had one of these specially-wound Philtron (or NOS McIntosh) transformers (or two or three or whatever.....), could I work with an electronics shop to assemble what is essentially a McIntosh MC-240? Is there a special magic potion or incantation, or perhaps some antimatter or fairy dust that is necessary to the process?
My next project will be my first, and I barely understand volts, amps and watts.

Your starting point is very, very much like mine was about a year ago. I saw a photo of a 275 and I was taken by its glory. Then I saw how much one was goiing for and I bought a Dynaco ST-70 instead and took the plunge into learning about tube amps. I had prior training in electronics and 'tricity and have tuned up old radios but getting into the history of old classic tube amps and the amps from old console stereos has really been a fun ''expedition.'' But I've found it's too easy to get caught up in an idea and find out it won't turn out the way you expect. Put everything on paper before you spend a lot of money. It's very hard to seperate the need to know how an amp works from the amp ''kit" / results when you have to troubleshoot what seems like a problem. Satisfaction is NOT guaranteed.
I am 53 years old. Had a fantastic childhood and a wonderful adult life, but I'm starting to get tired and I DON'T like some of the changes I see. At some point in the next few decades, I will check out. Willingly. I feel sorry for my kids.

...and now we have a smartphone with ''SURROUND SOUND"!!! Tomorrow we get a HD / 3-D Ipod that will store all of our medical data and transmit it in the background to all the insurance companies because we ''agreed'' to the usage policy on F***B**k.
I am guessing there is a premium for originality. In other words, you pay for the "McIntosh" nameplate. An MC-anything goes for upwards of $5000. I'm guessing a guy could commission a clone-build for $3000.


Probably some guys posting here could be able to do that but . . . I suspect they are more interrested in new design than copying an old (as good as it can be) one.

About cars, some guys are probably able to rebuid a "Citroën Traction Avant" (I name this one because I'm French) from the scratch but would they do ? And if yes at which price for something that will stay a copy ?

One of the nice things about the Mac amps is the output transformer lets you dial in the impedance of your speakers. If you have this information on hand before you build you can get output transformers which are not multi-filar wound and will drive just the speaker load you need. You may still want Bi-filar windings. This will save money. Also, the early units were Point to Point assembled without complex PCB's which makes diy even easier. If you can get a good legible schematic and a chassis the correct size all of the other components are rather common. You will also have access to superior capacitors, wire, tube sockets, resistors.

You should be able to construct a very high quality Mcintosh clone, will not be cheap, that surpasses you own expectations. Much attention to detail, ask questions here and choose you components very carefully. Also, follow all of the basic practices when routing power and signal wires.

This is a fabulous hobby and very rewarding. Tad
Search DIYaudio for Norman Crowhurst's "Twin-Coupled Amplifier". Probably a few threads here. Same thing as Mac, but using ordinary off the shelf output transformers. Several magazine articles online too. Then you can decide whether to go whole hog for the $$$$ Mac OT, or stick with the Twin-Coupled, or even disassemble it for parts and make ordinary amps using the Twin-C OTs.
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