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McIntosh "Samra Style"

Posted by mr9iron (A) on January 17, 2017 at 01:49:09

Many of you inmates have seen some of my Citation restoration posts; something a little different this time...I was wondering if I could get my hands on a pair of McIntosh mono blocks and see what kind of a project it would be to restore and upgrade a pair. Those large chassis seem nice and room-y underneath, easy to work on :).. Of course trying to find something one can afford for that name is tough sledding for a man of "modest means" -Luckily, over the summer, when audio is not so hot on the e-bay market, some bidders fell asleep and I picked up these Mc40's for a decent price. They sat around for little under a year while I researched a restoration plan..

I say "research" but I already had a good idea of what I wanted to do..I had seen Samra's posts on his Mc30's and the like, he's done quite a number of "Macs" recently. I asked him about his "devious methods" and parts selections. Mikey, as per usual was more than helpful, and lent his suggestions. His beefed up power supply with poly-films will really bring out the potential of the "Mac" so I studied his set ups and found sources for the parts. I know you can get the kits, and drop in replacements for these, but those parts do not necessarily yield the best results.

Mikey didn't have to hold my hand as much on this project, as it seems I am getting better at trouble shooting and picking better restoration procedures. However, it always feels like I will succeed when I know he's there to answer specific questions, or even just talk theoretically or in general, he lives for this stuff, and it's almost as if he's a regular help line operator.. :)

Here are some of the highlights:

Panasonic Poly-film filters replace the original B+

Nichicon 820 UF doublers like the Citation mods..

Poly-film bias supply filter

Cree Schottky Diodes

Of course, K40 and Vitamin Q coupling caps to replace the old Spragues.

This is how they arrived, of course I did my usual clean up and spit polish.

With a decent quad of Russian KT66 and all this work, I bench tested these amps with a perfect 1khz wave and they easily put out 57 watts RMS. The amps are dead silent at idle, thanks in part to the power supply and a 12 gauge ground bus I installed..

Now I know the MC 40's are not the darling of the McIntosh line up, but when you use the "Samra" formula these guys "shit and git".. and at the same time remain quite musical. Tight control on the bottom end for a tube amp, yet graceful clear and very "layered" from the mid to the highs. I prefer the solid state rectifiers in tube amps. I know many of you will say that's sacrilege, but I like the firmness it provides. It's like you get the best of both worlds. The Schottky Diodes are pretty amazing, this is my first time trying those..

When I first got into tubes I picked up an MC 240, I had it brought up to "working" by a good tech, but I never heard the true potential of the amp, I just thought it was "alright". I ended up selling it due to financial reasons, plus it just didn't quite hit home. Now years later after learning how to do my own restorations, I feel like I finally got to hear what the McIntosh sound is all about, and what these amps can do.. As always a big huge thanks to Mr. Samra.. (Mikey) for showing me the way and making me a "Mac fan"

J

• MC 40 test run   (Open in New Window)

Edits: 02/07/23 02/07/23

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