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Tube Amp for Martin Logan Speakers

Hi, I love tube sound through my Martin Logan Aerius-i fronts and Cinema-i center. I currently have a Butler 5150 which is a hybrid, but it busted on me and would cost $700 to fix. I've had china stereo tube amps that were pretty good and gave true tube sound, but not enough drive for higher volumes. I live in condo, so not like I can blast music anyways but still. I got the Butler because I wanted 5 channel tube sound for home theatre (The piercing sound from my Denon 3801 receiver was not pleasant to my ears). It appears there are only three multi-channel tube amps around, from Mcintosh, Butler 5150, and Dared DV-6C. The latter two are hybrids, and the last one was one of the worst tube amps i've ever heard. I have no clue why 6Moons gave the Dared a 2010 award, but maybe it's because it produces only 65W.

So since multichannel tube amps are hard to come by, and they tend to be hybrid, I was thinking maybe it would be best to get three true tube monoblocks to power my fronts. Thing is I wonder if they will be underpowered for my speakers, and not sure which ones are decent for the price. Maybe China made ones would suffice, and they still go for pretty expensive price. I'm wondering if anybody knows of a decent powerful tube monoblock that is affordable, because I can't pay $3000 per block. or maybe best to just repair my Butler. Thing is, I'm not confident that it is reliable. The tubes are soldered in which is weird, and i've taken it to a couple repair guys who both said that the design is not good, because it's very tight inside and more susceptible to being fried from DC voltage areas. it's too sensitive.

Any suggestions for tube monoblocks, even if china made ones? the holy grail for me would be Mcintosh tube amp, but they are hard to come by. Thanks.

smurfmand70
bifwynne
2,206 posts
 
Tom, you quote the ML manual as advising that "an ideally stable amplifier will typically be able to deliver nearly twice its rated wattage into 4 Ohms and should again increase into 2 Ohms."

My take-a-way is that ML recommends using a rock-solid stable SS/Voltage Paradigm amp, which as discussed above has a very low output impedance. Stated differently, the ML ESLs in question were likely voiced to be driven by a SS amp.

Hence, based on what Al explained, using a tube amp which has a "high'ish" output impedance will likely result in sonic coloration to some degree. As Al also said, some may not find this to be a problem and that's ok. :)

So ... after all that has been written, I think the best answer to the OP's Q is that if he/she really wants to use a tube amp to drive his/her ML ESLs, consider a low output impedance BEAST that can deliver serious current.

Frankly, I would be biased (pun) in favor of using a high quality/high power SS amp e.g., a Pass, Ayre, Bryston, inter alia.

Regards,

Bruce
georgehifi's avatar
georgehifi
10,312 posts
 
03-31-14: Tomcy6
Of course not every amp can handle the job when you've got a speaker that has an impedance of .5 ohms at 20khz. But you don't need a lot of power to reproduce most musical content at 20khz either.

True, but if the amp cannot keep constant voltage at 20khz it will result in the treble being shelved down no matter what volume level you are listening to, resulting in a softened treble, some unexperienced might call this smoother, but their having themselves on.

(as the sterophile test reports state)
Quote Sterophile: " The shape of the impedance trace will result in the Montis's top octaves shelving down when the speaker is driven by a tube amplifier having a high source impedance. This is why Robert Deutsch found that his Audiopax amplifier sounded too soft and lacking in definition."

Cheers George
mapman's avatar
mapman
22,389 posts
 
"Hence, based on what Al explained, using a tube amp which has a "high'ish" output impedance will likely result in sonic coloration to some degree."

Yep. The specs give you guidelines but cannot answer what sounds best in each case. The key part is "to some degree". The question is always which colorations and to what degree. The answer will be different likely in each persons case though the specs might indicate certain approaches to yield the best results overall.
mapman's avatar
mapman
22,389 posts
 
Its funny how there are always two ways to look at good sound.

1) technical
2) practical/case by case

Nothing guarantees each perspective will resulting the same choices/solution. Why should they each case is different even if for no other reason than room acoustics and how each person hears. Would we expect two people to choose the exact same pair of shoes? No. But we all kinda know what makes some shoes better than others. That's the technical perspective and the only one of global value. But then , the shoe gotta fit....
mapman's avatar
mapman
22,389 posts
 
"In otherwords it will do the classic thing that can happen with low current or high output impedance tube amps "behave like a fixed tone control" instead of being flat into all loads."

That's a very interesting analogy!

I suppose, its a question of who is in charge, ie which component is going to dictate the parameters of the overall system that works best.

It makes sense that from the perspective of the amplifier or specifically the designer of a tube amplifier, they want their baby to be the one in charge.

The speaker designer trying to make a compact quality speaker with extended flat bass response that most might be willing to put in their rooms has a different perspective. The price paid in this case is more demand on the amplifier to help deliver the desired results.

Two different paradigms/ways of approaching things as Ralph likes to point out, each with unique strengths, weaknesses, and tradeoffs. Its good to be able to have the choice.
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