Can my MC275 power speakers with 91db sensitivity

I have no experience with the MC275, but from a technical standpoint I suspect that there is some validity to Polk432's point. The current (Mark VI) version of that amp has a specified damping factor of 22, which is unusually high for a tube amp. Correspondingly, its output impedance is unusually low for a tube amp. That suggests that its design utilizes a greater than average amount of feedback for a tube amp.

Everything else being equal, all of that will shift its sonic character in the direction of being more akin to typical solid state sonics than would otherwise be the case. In numerous ways: A reduction in effects on frequency response flatness resulting from interaction between amplifier output impedance and variation of speaker impedance as a function of frequency; reduced Total Harmonic Distortion (THD); better bass damping than would otherwise be the case; increased Transient Intermodulation Distortion (TIM); a reduction in some lower order harmonic distortion components that tend to be numerically greatest but are relatively inoffensive; and an increase in some higher order harmonic distortion components that tend to be numerically smaller but are more offensive.

Elegal, re your last question, if you want to consider going to a different amplifier you should settle on a choice of speakers first, and then choose an amplifier that will be synergistic with it. Some speakers are designed to sound best with solid state amps, some are designed to sound best with tube amps, and some will do fine either way. The Daedalus speakers I use are an example of a design that will do fine either way. Their output will reflect the intrinsic sonic character of the amplifier that is driving them, but there will be no issues relating to amplifier-speaker interactions with either type of amplifier.

Regards,
-- Al

I believe the original Cremona were rated at 90dB and the Cremona M at 91dB. The article that Al linked to was for the original Cremona. I believe the M are in fact easier to drive than the original Cremona. I have the original Cremona and concur that they are picky about amplifiers. I tried many amps and ended up with a Levinson 432, which does 400 watts are 8 ohm and 800 watts at 4 ohmns.

I would be cautious of your amp with the original Cremona, but it might be OK for the Cremona M. Unfortunately, I do not believe that Atkinson ever measured the M.

Jimmy, I have owned the Mac275 and the MC7270 SS amp. Both were good amps, but the Mac sounds more SS than tube especially when compared to my Cary V12R and CAD120's amps. One thing I really liked about the 275 is that it ran so much cooler than the Carys, just didn't have the warmth.

It can but probably not optimally along the lines related by Al.

That's not to say it won't sound good or meet your needs/expectations, only that you have a good chance of doing better in terms of both volume sans clipping and balanced and clean bass response and lower distortion otherwise as well perhaps to the extent that matters if you become so inclined.

So you can look at these things from the perspective of ideal technical matches that maximize performance, ie the perspective of intelligent "audiophiles" for the most part, or from the perspective of does it sound "good" or "good enough". Improving usually comes at some cost.

So its very much the oft cited "your mileage may vary" type scenario.

If that bothers you, then probably better to seek out different speakers that are more efficient and tube amp friendly in general.

Al's speaker recommendations are good ones. I might toss in Triangle and many Focal/JM Lab speaker models as possibilities.

Even Magneplanars could work very well with a tube amp like that, especially if very high volumes are not a concern.

OHM is another line that is perhaps not as tube amp friendly as some, but offers good value and decent performance with a higher power tube amp.

Adding a powered sub or two and offloading the low bass to that opens up a lot of additional popular speakers choices. That's a popular option for many OHM owners that use tube amps in some cases (some might go sans sub)and also for most any good quality speaker, including SOnus Faber.

Also, most any good quality horn loaded high efficiency speaker (mid 90s db efficient or higher) would be very good technical matches for that amp. There are many very good makers of high efficiency horn loaded speakers out there these days. Take a look at Cathedral speakers out of Virginai for an example of good sounding horns I have heard that can be had for very modest cost.

Electrostatic speakers are another good option to consider if that kind of thing might float your boat.

So basically, there are ways to make that amp work very well indeed with most anything if done right.

Hope that helps.

Elegal, ... Al, Ralph (Atmasphere) and I have been around the block on amp/speaker compatibility issues so many times, like the proverbial tiger who chased his tail and turned into butter, I feel like I'm about to turn into a stick of butter too.

As a threshold matter, let me say that Al's advice is spot on. Let me amplify what he said with a real experience. I've use ARC tube amps to drive my Paradigm 8 V3 speakers.

Although the S8s are pretty sensitive, 92dbs, they have impedance and phase angle curves that are so rocky they would make a mountain climber dizzy. To add insult to injury, the impedance curve in the bass through midrange spectrum is 4 ohms and the phase angle dips to a negative 60 degrees at one point. In short, the S8s were designed to be driven by a high current/high power SS amp. Ooopps.

Why the long tale? For some reason, my old amp, an ARC VS--115, was able to drive the S8s. Why? Here's my guess. The VS-115's rated power output is 120 wpc. Plus, its output impedance is "low'ish" for a tube amp. So the amp performed "SS-like" as a "constant'ish" voltage source.

But here's an interesting twist. I switched out my VS-115 for an ARC Ref 150. Now my speakers really sing. Why? Here's my guesses.

First, the Ref 150 has more head room by way of rated power than the VS-115: 150 wpc versus the VS 115's 120 wpc.

Second and possibly the most important. The capacitive power supply in the Ref 150 is 3 times larger than the VS-115: 1040 joules versus 334 joules, respectively. That's a lot. What this means in plain English is that when the Ref 150 is driving my S8s in the rocky road region, it can push some serious juice with its beefed up power supply.

Your take-aways.

(1) More power will not hurt, even with so called sensitive speakers. If in doubt, and your wallet can afford it, opt for more amp power. Even if a "marginally" powered amp seems ok, an amp that can handle the peaks and valleys of power demands, either relating to dynamic swings from the input source material or rough impedance and phase angle curves, I suspect your system with sound even better with more power.

(2) As Al said, first pick your speakers and then your amp. I was lucky because I did it half-arsed backwards.

(3) Read the many threads on A'gon which speak to speaker/amp electrical compatibility. Focus on Ralph's White Paper which discusses so called Voltage Paradigm versus Power Paradigm amps. Try to get your arms around the notion of how speaker impedance (which varies as a function of frequency response) can affect the sonic presentation if the speaker is driven by a tube amp with "high'ish" output impedance.

And, as I came to better understand, not all tube amps are "pure" Power Paradigm amp. If a tube amp uses NF, which as Al said will lower output impedance, the amp will perform "SS-like." Kinda like a hybrid.

(4) The use of excessive NF in either a tube or SS amp to achieve certain operating objectives (e.g., lower distortion, extended bandwidth, higher DF) does not come without sonic costs.

That's it.