McIntosh MC 275 Mk IV or V with Harbeth M-40.1?

I've had my Plinius SA-102 for longer than any previous amp (almost 3 years) and have been very satisfied with it's reliability, musicality and build quality, but I'm very intrigued with finally trying a classic tube amp.

I listen to classical, jazz, vocals & acoustic rock at moderate volume levels, so I'm thinking the 75 WPC of the McIntosh MC 275 (mk IV or V) would work fine in my 15' x 21' x 7' basement set up. The Harbeth M-40.1's sensitivity is 85dB/W/m, 6 ohm nominal. Suggested amplification: >50W (Stereophile's review of the M-40.1's noted excellent success when driven by a 35wpc Shindo push-pull amp)

I've researched other tube amps from Rogue (M120's & 150's), VTL (ST-150), Manley (Snappers), Cary (120S), Audio Research (VT-100 MK III) and Quicksilver (V-4's). Ultimately I'm leaning heavily towards the Mac MC 275 (Mk IV or V) due to its not being a monoblock, it's a classic unit with excellent build quality and good resale value, and it's known to be reliable and is easy to bias.

Preamp is an Aesthetix Calypso with NOS tubes and my sources are digital and FM.

Comments from those experienced with later model McIntosh MC 275 and/or Harbeth M-40.1's would be appreciated.

Thanks - Paul

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I have a (2) MkV (Mac 275) along with the Aesthetix Calypso. The combination of both is quite good. I have two Mac 275's and they are used in mono. However, I had also used one on my system with very good results.
The Mac is a bit dryer then the Aesthetix and therefore they complement each other. My 2 cents!

Rick - are you using stock tubes in the Mac 275... and if not, which ones are the most critical to replace as far as sound quality goes? I use select NOS tubes in my Calypso and the difference is night & day.
The McIntosh has the highest resale of any electronics.
I am using Telefunkens in the 12ax7's and 12at7's bought here on 'gon.
Big (positive) difference. I have not changed the Kt88's butI plan to. Neil (one of the great cotributues here) knows quite a bit about the Mac 275.

Rick (RWD)
I believe Rwd is referring to Nsgarch when he says Neil. He is indeed knowledgeable about the 275.

I also have a 275 mk IV (I love it), with rolled 12AX7 and 12AT7. These signal tubes are said to have the highest impact on sound quality. I have not yet rolled the KT88 so I cannot really comment from personal experience.

About your question: since your preamp has RCA and XLR connections, I'd say if you plan to drive the 275 from the XLRs, then either the mk V or mk IV would be the same. If you are going to drive it from the RCAs, I'd say go for the mk V. The mk IV has volume pots in the signal path when driven from RCAs, which allegedly degrade the signal. Both the mk IV & V add V1 tube to the signal path when driven from RCAs as compared to XLRs.

FWIW, I drive B&W 804S which are 90 dB speakers, and I'm happy. Can't claim to have tried a gazillion amps, though.

My two cents. Hope it helps.

Lewinskih - Yes I will be using RCA cables, so you advise is pertinent... thank you. One question though.... when you said add "V1" tube to the signal path, what do you mean by V1?
Stuck a deal for a MC275 MK V. Really looking forward to rolling tubes in my 1st tube amp!
Good luck with your purchase! Hope it works out for you, I'm a big fan of the MC275.
Pdreher - V1 is the first small signal tube(marked on the chassis), that the signal encounters in the amp(when using RCA cables), therefore it has a great effect on the sound. Balanced sections are very important as is the quality of the tube. The 12AX7's affect the sound the most, followed by the 12AT7's. Roll them in that order, if funds are tight. Good luck and have fun.
Paul, please let us (me) know the results of the GL KT-88 power tubes you plan to use in the Mac 275. I am also considering changing my power tubes but not sure about Gold Lion (re-issue) or Penta??


Rick (RWD)
Rick - On Neil's (Nsgarch's) advice, I plan on sticking with the stock Svetlana KT88's for now (due to limited funds), but have NOS RCA triple mica black plate 5751's and Sylvania tmbp 6201's I purchased from Neil that I will experiment with this weekend when I set up the MC275 mk V for the first time :o)

I may be in position to try the GL reissues in a few months.
So hows the amp working out so far?
Tom - so far, so good. I'm currently listening with all of the stock tubes to get a feel for things, but have the NOS RCA 5751's & Sylvania 12AT7's ready to roll. Surprisingly, the amp sounds really, really good with just the stock tubes... a very pleasant surprise ;o).

The MC275 with the stock tubes is lacking the detail & refinement provided by my previous amp (Plinius SA-102), but it's noticeably more musical, natural and robust sounding without being in your face... I'm really loving it! Will be interesting to see if the NOS signal tubes take the sound to a new level.
Hope it gets even better for you. Does the drop off in power seem to be an issue with the new amp?
The drop in power suits the M-40.1's just fine. I do have to turn up my preamp about 5 more db's to get the same volume, but the speakers are not lacking any grunt. If anything, the sound is more full & robust moving from ss to tubes, at least in my particular situation.
My father had the original 275 for 40 years with never a sick day. I concur with the 40.1s--incredible speakers that will play to the amps strengths. I can also recommend ATC 19s and Spendor A6s.
IMO, I would think the Mac with the 40.1s would be too much of a "good thang".Never heard them together ,only in seperate system and wouldnt own either..guess thats what makes this an interesting hobby..
Toetap - Before making the plunge, I too was concerned that the Harbeth / McIntosh tube amp combo could be "too much of a good thing"... but IME, the two really sound great together.

I know your not a fan of either Harbeth or McIntosh, but I recently left behind several years with Dynaudio C2's & C4's driven by solid state... and while those combos provided exciting & exhilarating sound, I've found I prefer the more relaxed & organic sound provided by the retro combo of the Harbeth & Mac tube amp. I think some of my change in preference has to do with age (I'm 45) and musical preferences.
Glad the McIntosh worked out for you. The 40.1's are truly great speakers and I can imagine wonderful music being reproduced in the room by the glowing tubes of the McIntosh MC275. Hope you would attain an even higher level of sound and musicality with the use of different/higher grades of tubes.

Musical preference always matter in this hobby as everyone hears things differently. Hence it is important to mix and match components in getting the ideal sound that the listener wants. "Too much of a good thing" for one can be "just right" for another.

Have fun rolling the tubes. Enjoy~
Ryder - Thanks for the kind sentiments. I know you've been experimenting with various amplification for your SHL-5's. I highly suggest you buy an MC 275 MK V. I'm still listening with the stock tubes and Miles Davis "Kind of Blue" redbook CD has never sound so wonderful on any of my previous systems. This amp is something special and has really transformed my system ;o)
Hi Pdreher. Thanks for the recommendation. Will keep the Mac in mind. I knew the MC275 was something special since the sonic attributes appealed to me even though I was using a pretty lousy preamp on it the last time I tried the MC275 MkIV. Still trying out some amps to get a feel of things to come. Will get to listen to the Naim XS in my system this coming weekend, hopefully.
Pdreher..I understand that retro thing as at one time I collected vintage Mac tube amps and ran JBL/Tannoy/Altec for years.Much to my surprise I found what was really missing when I drop coin on a pair of Avalons over 10 years ago.Detail,energy,dynamics,huge 3-D soundstage etc and I never looked back.McIntosh has that cult following and yes it has super resale value but certainly not in the same sentence with any of the forementioned attributes.The same applies to Harbeth excluding resale value.Like I stated we all have our opinions and own taste, thats what makes it fun and interesting OBTW ,Im actually older than you so dont blame age for stepping backward LOL.Enjoy the system
You are right Toetap, some of us like the way real music sounds, and the 275 reproduces music in a more realistc and enjoyable fashion than any amplifier I have heard regardless of cost. Unfortunately, for me, it took many years and many lessons before I finally broke down and admitted to myself that McIntosh equipment has a high resale value for a reason. I did not want to admit it to myself for a long time. The 275 is one of their very best and is an absolute steal for the money. Harbeths sound nothing like JBL's by the way. As far as Avalon's are concerned they are good speakers no doubt about it, but the Harbeths sound pretty good and the gap is nowhere near how you put it. Have you ever heard Harbeths? If you did, you would know this. The Avalons have more bass but I am not sure that necessarily makes them better as in a revelation as you put it. Bigger isn't always better.