Discussion in 'McIntosh Audio' started by sancho22, Feb 10, 2018.
As 62caddy says, a properly rebuilt MC30 will put out 45+ watts.
yes, the MACs are conservatively rated. for all practical purposes, and they are overbuilt since they were designed to put out that power level all day long....not many amps will do that.
25-40 watts is not much different in power. What is different is the sound of the tube 6L6GC vs. 7591, and sand rectifier vs. glass for the '30.
I had a pair of MC75s and MC60s, basically the same amp; but one has tube rectifiers, the other has sand....the tube rectifiers to me do sound a bit more musical....so sold off the 75s and bought another pair of MC60s....
and I know this is sacred ground for some, but the MACs can be scary good if you replace those bumble bees with some Jensen copper foil caps. very organic type sound, and tremendous hold your butt in the listening chair power.....
There’s another significant but frequently overlooked difference betw the 60 and 75 (275): The 75’s OPT employs a tertiary CT winding in same turns ratio as the two primarys. The “ends” of the winding supply the anodes of the 12AT7 CF drivers while the CT is supplied with ~ 1/2 B+ (235V vs 460V).
Not sure how this OPT/circuit difference contributes to the “sound” of the 60 vs 75 compared to vacuum vs SS rectifiers. Probably difficult to separate the two factors from a practical perspective.
I have multiples of both ..... you can not lose - these are the best Mcintosh amps in my opinion
Slight preference for the MC30 but would not wait if I saw a 225
How does the 240 rank vs the 30s and 225?
Short Answer: Just more of the same .
Despite my snarkiness, once restored well, you'll be hard pressed to tell the difference with any of these amps when fed with music sources and speakers that can reveal them.
In this thread, I believe we're talking about nuances and impressions from many different perspectives. Further, the fact that, 50+ years after they were introduced, we can be here debating these amps in this way is amazing.
MC60 are bass monsters
240 is a fine amp but not as good as the MC30 or 225 in my opinion
In all stock form, would tend to agree, but once hot rodded the 240 takes the top notch of the three, but we're not talking huge differences here.
For all MAC amp users, another inexpensive thing to try is replacing that first stage 12ax7, with an AT7. You will lower the forward gain of the amp slightly, but at the same time reduce the level of GNFB. The amp will sound more relaxed than stock. If you like that sound you can rebias that first tube socket by cutting the 100k plate load resistor down a bit to bring up the plate voltage back to around 100VDC.
And as long as you have the bottom cover off, replace that OEM 100uf 3V polarized cap in the feedback loop with something newer and better and add a .47 film bypass cap in parallel with it....that change alone will improve the focus of the amp, and make a bigger change vs. comparing any of the models to each other in stock form.
Also, women's hearing tends to be better than men's after age 35 or so.
I am in Mendham. Really appreciate the generous offer!
I agree women do have better hearing. My wife can pick up subtle nuances when I swap cables better than I can...
225 is a special unit with a very special sound. But that said separates normally trump combined units. A 225 will put out 34 watts while a MC 30 will put out close to or just over 40 watts. But the MC 30 used tube rectifiers which add to giving the MC 30 that special warm sound some tube owners demand. 225 I always found to be less colored than a MC 30 and the highs superior to a MC 240. But you must have efficient speakers with a 225. I would say 98 db 4 ft 1 watt as a minimum. 225 worked Great with Altec, JBL, EV and Klipsch with higher sensitivities. TWO of my favorites were EV-6 or Klipsch Cornwall. In a smaller room you could squeak by with any of the Bozaks as long as you don't need big bass. Thats 275 and 2105 territory for 305's, 4000 Symphony, and Concert Grands. I have a 2505 and its a 70 watt amp if up to snuff. Its a great amp. I use it to drive my Signet Electrostatic and smaller Stax electret headphones. The Lambdas have their own dedicated Stax unit. I tried one of my 240's as a headphone amp and the 2505 was much superior so I can understand why you prefer your 2505. I would like to try a 7100 though. 10 or 15 db more signal to noise and ,005 maximum distortion versus 0.1 at the extremes with the 2505.
My view is simply this: If you really want and can afford a McIntosh tube amplifier in top grade condition, by all means go for one. It will last for many years, will outperform many tube amplifiers being produced today, will always maintain its value while being a thing of beauty. However, an MC250, MC2505 or pair of MC50 will perform just as well for significantly less money, will maintain value just as well, while requiring far less maintenance.
Whatever sonic differences that may exist between all models mentioned here are on a very small order of magnitude. I would not recommend buying into tubes with expectation of any dramatic performance transformations. One man's opinion.
Concerning power - Forgot to mention I run two MC225 bridged - I will say I never had an issue when I used a single unit as stereo. Outside of electrostatic speakers i feel the general "lack of power" argument is not valid.
Lots of nice info.... I can only comment that I LOVE my mx110z paired to the MC40’s.... they are stock and use all the original tubes.... feeding my usher be-10 and the sound is outstanding.... very very engaging, I can listen for hours and hours without fatigue...
Will look into restoring them... but meanwhile they are performing so nice that it breaks my heart to make them go though major surgery....
Slightly <more> off topic, but perhaps relevant to some of the sonic quality & preference comments here regarding certain amps.
Since I recently bought a cap analyzer (Sencore LC77) I've tested most of the original mylar caps in my vintage gear and 80% of those caps are leaky at rated voltages. I'm not talking about Bumble Bees, they go right in the garbage, but the 160P Black Beauties that most people assume are fine in these amps. After completely rebuilding these amps I had left 4 of these caps in two pieces of my gear assuming they were fine. I now intend to change them to modern equivalents that are in spec.
I hate the idea of rebuilding a vintage, virgin piece of gear, but it just has to be done to get true performance out of them. Unless rebuilt to spec, any judgements and comparisons of these amps should be taken with a grain of salt. Just my 2¢
Arizona caps are great replacement for Bumble Bees.
Agreed, as are Russian K40Y's and many film/foil caps. K40Y's test so close to rated spec it's scary, but then again they are mil spec caps.
Consider contacting Jim McShane for his recommendation on replacement caps.
I'm considering replacing the oem Goodall caps in my Marantz 8, but haven't made a decision since it is quite clean otherwise and biases properly, and would seek his recommendation if I decided to do so.
I am thinking piggyback using 50/50 of Mundorf gold silver oil and Arizona blue
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