Ideas for Biamp with mc611 and mc275?

Instead of buying one of the new combo Mcintosh solid-state tube amplifiers (mc451 or 901), how practical would it be to get 2 mc275s (each set to mono) to biamp speakers along with the mc611 solid state mono?


Huh? Like 2 amps per side with the 611’s driving the bass and the 275’s driving the mid and treble?

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May work but there could be a gain problem where one of the amps is playing louder than the other.  Call Audio Classics first and see if it can be done.  They are the experts, they will know for sure. 

Excellent point, you have no control over each amplifiers spread of signal to different drivers.

Audio Classics has tons of used gear.

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Active is the only way to go. And don’t forget to bypass the internal speaker crossovers!


How does one go about bypassing the crossover's? Is this a DIY exercise which I guess requires you to go inside the speakers and remove the filters and have the drivers directly wired to binding posts.   

Yes, you will need to access the drivers and binding posts and disconnect the internal crossovers from the binding posts. Or simply add another set of binding posts. 

Men 220

Not sure I understand the value of a men 220.  Unfortunately it doesn't come with Home theater capability, and it doesn't provide a graph of your room situation.  It's a box that requires you to test the room and then it comes back with a room correction for all those pressure amplitudes that may be out of sync. Basically it cost $6000 to treat your room, and then you leave it connected to your system. It does provide crossover capabilities but that's a small piece of it I guess.

It does seem woefully over priced. 

It can be done but you need to preamps/volume controls.

the first preamp needs two outputs. One would go to the less powerful amp and then one would go to the second preamp/volume control then out to the more powerful amp. This way you could adjust the balance with the second preamp then use the first one as a master. 

For what it is worth my local shop was playing around and use a MC275 and MC7200 to byamp a pair or 805D3s. I did not listen in extreme detail but it sounded nice on the surface. 

The Men 220 has crossover controls that you will need to send the signals from the 2 different amps so that they do not try and play the same signals to the speakers. 













I’ve done this for years and it sounds excellent. are use the Macintosh C50 pre.  Speakers are Tekton Moab with the bi-amp crossover. Everything sounded balanced and perfect, except that I had cleaner base, more base, actually and warmer mids and Highs.  I have to believe that the mackintosh MC 451 amp is maybe a little bit better because it was designed exclusively for the task at hand.  I believe it’s called horizontal bi-amping.


What crossover device do you use for bi-amp?

I saw your system, is mc275 used for the higher ends?


My speakers were designed as a bi-amp speaker. There were four connections on the back of the speaker cabinet instead of 2. If that’s what your speakers have been, you’re fine the speaker company has designed it to be crossed over inside the speaker. When the signal gets sent from the amplifiers, they both send a full signal. The crossover is what filters out what the speaker wants. If you don’t have a speaker that is designed with that kind of crossover then you’re gonna need to rip out the existing crossover and use an electronic crossover. 

I looked up your speakers, and you are good to go. Just take two separate outputs from your preamp and put them into the two separate amplifiers. The magic happens inside the speaker. For instants on the back of your preamp, you may have a RCA set of outputs and a XLR set of outputs. Run the XL wires to the MC 275 and the RCA’s to the MC 601. You’ll be good to go because the preamplifier will feed the voltage to each amplifier at the same rate. If you don’t have two different outputs, then just use a Y splitter and runs one of each to the amplifiers. That’s it you don’t need anything else. Hope this helps. I’ve been doing it for years and it sounds great.

So I have been thinking about biamping with two MC601s and one MC275. My pre is the c2300 that has two outputs and my speakers are set up for biwiring. 

Would this work or would I need two Mc275? How do I control the gain differences?  The c2300 allows adjustments of gain for each input but I’m not sure it does for each output. 

I applaud your initiative. Unfortunately, it is clear not many have ventured into this territory. There is very limited guidance, and Many I hear go back to the way it was

I’ve tried to learn about this and most are very unclear what Will happen. There are voltage differences between different amplifiers that will require level adjusting via crossover I guess.

And then you are faced with constant manipulation and in light of all the various recording Quality differences I am not sure if it’s worth going down this path. And you could have a result where it doesn’t sound very good

I looked at the amplifiers designed for biamping from McIntosh, 451 and 901 and they look very good. And expensive. However, these things generate a ton of heat. The 901 is the equivalent of a portable heater set to low continuously.

The 901 uses about 900 Watts from wall when in use which translates to 3000 to 4000 BTUs, which equates to about 10 bodies in a room. A human generates about 300 BTUs  sitting on the couch. And those that buy these amplifiers have dedicated air conditioning to minimize the heat impact. If you’ve ever had a lot of people in a room it gets very hot very quickly, and that’s what these amplifiers do to your room.

Quality tube amplifiers lose their appeal in this situation which is really sad. Maybe a lesser Power amplifier from Mac, ie 275 Will be perfectly wonderful for the upper range drivers. And I would especially be interested to know how biamping works out. I was tempted to try the mac stereo 1501 which is less powerful and generates less heat.

Another huge problem is all the additional cables you need to deal with, which offers all kinds of new challenges especially if you have a great speaker cable that now has to be supplemented with other cables.

So many issues.

There's been multiple questions about this lately. Will be a little long, but hopefully this info will help get some over the hump to give it a try. I've horizontally and vertically bi-amped at least 20 different configurations(lost count) in recent years with varying levels of success, but each time improving with experience. Being a classic Infinity fan, most were with Infinity speakers including Kappa 8,9, Ren 90 and RS2B ending up with IRS Betas. Bi-Amping with the Betas and 2B's were easiest and most successful as both had a Servo or Bass Eq to adjust gain for the low frequencies for ideal match.

Pre-Amps used were Carver C19, Sunfire Tube, Mac C70, C1100 and currently Ayon.

Amps used were several different Carver/Sunfire/Lightstar combos, then McIntosh 275 single and monos with Bryston 7B's for lows; later replacing with MC2301's and Legacy I-V2 all leading to my current Analysis Orions which are actually Tri-Amped using MC901's and Speaker Power Monos on bass panels for time alignment and frequency/level adjustment in a full active set up using the MC901's internal crossover as well. It is true that you tweak until you figure it out, but when you get to your sweet spot it stays pretty consistent.

Simple rule of thumb is to have double the power to your lows as your mids/highs. McIntosh demonstrates this with the 451 and 901. I'll say upfront that the 901's have bested every combo in every way, but they should for the price. The MC275's were one of my favorite for Bi-Amping. They sound smooth and sweet and reduce the chance of overpowering your mids/highs vs some other options. You can save some money going with lower cost but high quality SS A/B or Class D amp/monos for your lows instead of the 611's and apply those funds to an active crossover or even one of the few Pre-Amp options out there with adjustable pre-amp outputs.

Having owned all the Mac tube amps listed above, I can share first hand that heat has never been an issue. I live in the Southeast and listen all I want in the summer months in a listening room above my garage which is a room more challenging to cool with no issue. It's not even a concern.

You will need additional cables and interconnects. Use inexpensive options until you dial in, then upgrade as you want/need. The Mac 451/901's do save you a set of power cords and interconnects with their configuration and really make it easy. They bring a simpler, seamless experience if you are willing to invest in them. Mac is on to something, I wouldn't be surprised if we see a 75/150 option coming at some point.

Thank you very much for such an awesome comment, very helpful.

What crossover Device would make sense absent the Infinity IRS Servo Control Unit Device which I'm not sure can be used separate with other speakers, although it does seem ideally configured.

It is true I am very concerned about 901 heat generation, and I'm surprised you have no problems with that even with your 9 foot ceiling and larger room. Not sure if you've ever measured watts used from the wall when 901s are at idle and in use, but I have learned these things use about 1000 W while both units are in use, which is consistent with a portable heating unit set to low being run continuously..  I find it challenging to understand how these Amps can be used without on going AC to offset the heat. 

I did see you updated your pictures,  the 901 Amps look very nice, and I have noted the racks as well which seem ideal.

I have considered a 1501, or 2 275s, to go along with my 611 amps but the convenience of the 901 would clearly do a better job to achieve the biamp goal.


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@w123ale Interesting little piece. Wish I would have found it years ago. Yes, one for each channel should work. Great if you have two balanced pre-outs per channel, use a good quality xlr splitter if you don't. Good luck!

Forgot to mention in post yesterday that I also used an Infinity RS crossover that worked well with my speakers that didn't have a servo or bass Eq. I believe it was designed for the 4.5's, but can use with any speakers. You can still find them used occasionally.