1st Mcintosh... MC60 Monoblocks. Advice please.

biggal76

biggal76

Active Member
Hi,
I've been wanting a vintage MC amp for a long time and finally got a pair of MC60's. Right now I have them preamped from my Sansui G901 through my Klipsch Forte II's. They sound better than the Sansui's power amp section, but not as big a difference as I expected. I have to turn the preamp's bass up all the way to get the sound I am looking for and then it seems a little thin in the mid-bass. I think I need to upgrade the preamp to something with tubes that is more well-matched to my power amps. I know everyone wants to recommend a C22, but I'm not ready to spend another $4K or so on the system just yet. Any recommendations for a preamp? I'm open to brands other than Mcintosh and vintage or newer gear. 2 things that would be a plus but not dealbreakers would be a switched 3 prong power outlet (or a pair would be even better) for my power amps and an integrated tuner.
I am also considering recapping my speaker's crossovers, but am not convinced that it will make much of a difference.
I should post what tubes I am running as maybe that is part of it. I'll do that this weekend.
Lastly, for some reason, when I hooked them up in my basement, they both hummed terribly and sounded pretty flat. I had them hooked up to my Denon home theater pre-outs set on Bipass mode, so that the sound path is supposed to be direct from my Blu Ray player into my amps and speakers are Klipsch Cornwalls. I cannot figure out why, but I have a Sherwood tube amp that also hummed and didn't sound as good down there as I thought it should. I believe the problem is in my electric line, because it hums even when a source is hooked directly into the amp, not through the preamp. Any thoughts on what would cause this? Would a power conditioner fix this?
 
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Hi cant help with your basement power issue but I can mention what my buddy runs in his Mac 60 system,he also is a tech and weve both collected gear for yrs and moved up the audio ladder together
He runs a fully refurbished Harman Kardon Citation 1 tube pre and a hhscott tube tuner with his Mac60 mono's,turntable is a Thorens and a hi end modern CDP
For speakers he swears by the more modern Tannoy 15 inch dual concentric DMT series,

hunter
 
Try flipping the plugs over to tame the hum. Also try plugging everything into a power strip so everything is grounded the same way. If these MC60s are not restored they are overdue! That could make them hum. Try plugging the CDP directly into the MC60s and see if you get the sound you are looking for.
 
chef free said:
Try flipping the plugs over to tame the hum. Also try plugging everything into a power strip so everything is grounded the same way. If these MC60s are not restored they are overdue! That could make them hum. Try plugging the CDP directly into the MC60s and see if you get the sound you are looking for.
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Hi,
Thank you. They were restored/recapped, etc when I bought them. I wish I had specifics on exactly what was done. I am going to contact the seller and see if he has paperwork from the tech or any specifics. The cords were replaced with 3 prong and they don't hum in my upstairs living room, so I think the hum problem is with my electrical wiring, not the amps. I will try putting a source right into the amp and see what they sound like.
 
hunter00 said:
Hi cant help with your basement power issue but I can mention what my buddy runs in his Mac 60 system,he also is a tech and weve both collected gear for yrs and moved up the audio ladder together
He runs a fully refurbished Harman Kardon Citation 1 tube pre and a hhscott tube tuner with his Mac60 mono's,turntable is a Thorens and a hi end modern CDP
For speakers he swears by the more modern Tannoy 15 inch dual concentric DMT series,

hunter
Click to expand...
Thanks!
 
Tubes:
6550 tubes are Ruby 1402ASTR. They are Chinese but supposed to be a remake of vintage GE tubes. Smaller tubes are assorted but matched between the two amps. All appear vintage USA.
Will rectifier tubes affect the sound much? In one amp, they are old looking GE and the other amp are Rad Tel. I assume they don't matter much as long as they are working properly.
 
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Go to the local hardware store and buy a "3-wire receptacle tester" ($5-$10) and figure out whats going on downstairs. It could be as simple as a swaped wire
 
chef free said:
Go to the local hardware store and buy a "3-wire receptacle tester" ($5-$10) and figure out whats going on downstairs. It could be as simple as a swaped wire
Click to expand...
I thought of that as well. Outlets test fine. I'm going to run an extension cord from downstairs to the amps which are now upstairs and do some troubleshooting over the weekend. Anyone have opinions on the Ruby tubes? Preamps that are under $1500 that will pair well with the amps? I need tone controls to correct for bad room acoustics. Considering using an EQ. I'm not a "signal path purist". IMO, there is no way that one amp can sound it's best in any type of listening area without bass/treble correction.
 
Using a 3-prong cord on an audio component designed 30 years before 3 prong cords were first used in audio components isn't a good idea at all. Pull the bottom of one of the amps to verify if the green wire from the cord is indeed connected. If so, to where?
 
Congrats on joining the MC60 club! Listening to mine right now. Agreed with above comments about hum, particularly if it's on a specific circuit.

Hard to believe this hasn't been mentioned, but what is the service history of you MC60s? Your description of the MC60s being thin in the bass doesn't seem right. These are amps that do need some routine work to meet spec, 50 years after they were produced. Otherwise, they almost definitely aren't - and if you design your system around their current characteristics, you may regret it once you have them worked on at some point.

The crucial service includes:
  • Replacement of Selenium diode and bias resistor
  • Replacement of electrolytic caps
  • Probable replacement of the 12k carbon comp resistors, which require very tight matching. I've never seen an original set of these that still meets specs.
  • Strongly consider replacement of all Bumblebee-type capacitors, which leaked and almost always need it.
The first three are the most important. When I serviced the bone-stock pair I bought, I went further and replaced all of the carbon comp resistors as well (in my amps, the only original components under the hood are the Black Beauties, xformers, and chokes). They sound simply stunning.

In short, if they haven't had work done, that's what I would consider first.
 
Found the hum. It was a bad set of RCA cables I used from preamp when it was downstairs, so hum is not an issue.

The amps were serviced and "upgraded" but I do not know the details of what was done exactly I am going to email the seller today and see if he has any paperwork or knows more details, but I have a feeling he won't have any additional info.
 
Mc 60's were always known for that special tube sound. Mine were warm with detail an could shake the room using my Bozak speakers with out the need of any bass boost. So I would guess you either have severe room placement issues or your speakers are either not the right ones for you or have been damaged by clipping under powered amplifiers. But then it might be something simple as updating your crossover parts as a return to happiness.
 
SilverTpt999 said:
A couple pictures of the inside of the chassis would help us tell what has been done.
Click to expand...
The seller said he'd go see the tech that did the work on Monday and get specifics for me.
twiiii said:
Mc 60's were always known for that special tube sound. Mine were warm with detail an could shake the room using my Bozak speakers with out the need of any bass boost. So I would guess you either have severe room placement issues or your speakers are either not the right ones for you or have been damaged by clipping under powered amplifiers. But then it might be something simple as updating your crossover parts as a return to happiness.
Click to expand...
I'm using undamaged Forte II speakers with Crites tweeter upgrade. I do have some bad room placement issues that can't be corrected without a divorce, but my solid state gear has more bass than the MC's, in the same space, so I'm thinking issue is with Chinese output tubes, caps, or something in the amps. They sound good, but i expected more bass and a tubier sound. Basically, they sound a little smoother than my Sansui receiver but with a little less bass, but the difference isn't anywhere near as drastic as i expected.
 
"Tubey" sound isn't what McIntosh is known for - their tube amps are literally lab-grade, and they had clients throughout the military and science labs. They should reach well below audible before rolling off. The damping factor isn't as low as many solid state amps, which can result in slightly less tight bass depending on the speakers - but the actual amount of bass should be unaffected. Your Klipsch speakers should not have this problem.

My first and second thoughts are the electrolytic caps, especially the two silver cans that rise up next to the tubes. If your amps don't have the reserve in the power supply that they'd like, this can result in lower bass response as the bass usually requires more energy.

That is, unless your receiver is very bass-heavy for some reason, and what you're hearing now is actually accurate sound. Worth keeping in mind as an outside possibility.
 
Sorry to be blunt here...but....you spent a bunch of money on MC60's, why not give them the tubes they deserve? In my experience, Ruby tubes are crap, again, my experience and opinion. Get some good small tubes, Tele's or RCA black plate. And, get some good rectifiers. Now, as far as a preamp, I'd go with a C11 or an MX110Z.
 
I had a feeling better tubes would help so am glad to get some feedback about that. I hooked up an EQ to compensate and just had a great listening session. Love "She Caught The Kady"- Blues Brothers version. Also, "You Don't Love Me-Soul Serenade" (Allman Bros) at about 8:30 Soul Serenade part. Sounded fantastic but cranked low frequencies way up with EQ to get audio bliss. Best sound I've ever had no one of my systems...maybe best I've ever heard, so I'm psyched. When I replace tubes, does it matter if I get quad match, or just matched pairs for each individual amp? Again, part of the problem is room positioning. The sitting area is a few feet in front of a wall, so I don't get that extra bass from the sound reflecting off the wall. I know people love passive preamps, but different recordings are mastered differently in addition to differences in room acoustics, so I don't understand why some people don't like tone controls. I guess that's another topic though.
 
How far in front of your Forte II's are you sitting? Are they toed in, or firing straight? What is behind them? As you've discovered, Forte's can be very finicky placement wise, and given everything else, I think this is the biggest issue to try to rectify in some fashion. Your statement about sitting a few feet in front of a wall, and missing the extra bass is interesting. That extra bass is not exactly good bass, really...it's reflected, it's distorted.....With MC60's and Forte's, you want most of the bass hitting you in the face, not from behind. And, unless I've missed it, you haven't really described your overall room situation...such as length/width/ceiling height, side walls, windows, furniture, flooring (rugs, tile, wood, etc?) I guess a couple of photos would answer most.

It might be slightly more difficult to find a quad match, but shouldn't be too hard. And, it's not going to cost a bunch more either. As far as signal tubes, go for same manufacturer (within types), preferably very close dates, and same construction.

Jim Mcshane has some nice 6550's that won't break the bank...

http://www.mcshanedesign.net/tubes.htm
 
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