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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
 
Well that's kind of an important question Mapman because given the wacko impedance plots of these ESLs, hooking them up to a high'ish impedance tube amp could really color their sonic presentation if indeed these speakers were designed to be driven by an amp whose output impedance is measureable in decimals points.

And while in such cases ZEROs may "trick" a tube amp into thinking it's not driving into a short, the sonic presentation will still be skewed because the ZEROs will not flatten or "normalize" the ESLs impedance plot.
minorl
1,016 posts
 
Of course a call to Martin Logan company might answer your question with more degree of accuracy.

enjoy
georgehifi's avatar
georgehifi
10,312 posts
 
03-28-14: Mapman
My understanding is low impedance in treble region does not present nearly as much of a challenge as same in bass in that exponentially less power is needed for flat treble response. I think that is the main reason why tube amps can do well with those.

It will work into that load, but will be "as JA put it" "shelved down in the treble in this instance". This "could" give you the initial impression of a sweeter treble.

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.

This is where the Zero can be a bandaid fix, but I always believe it's better to fix the problem, by changing the amp or speakers to something that are compatible with each other, than to mask the problem by introdcing a pseudo fix that has it's own set of problems.

Cheers George

georgehifi's avatar
georgehifi
10,312 posts
 
Mapman, I just noticed that you have class D amps as powerful as they are don't think they are out of the woods when it comes to driving ESL's
Their achilees heel is driving low impedances in high frequencies, they behave in a similar fashion.
Just look at the black trace that is the frequency response of the Belcanto Ref1000 driving a simulated speaker load, see how it goes all wonky, it should be flat, and that load is no where near as severe as an ESL load in the HF.

http://www.stereophile.com/content/bel-canto-ref1000m-monoblock-power-amplifier-measurements

Cheers George
atmasphere's avatar
atmasphere
11,874 posts
 
So my sense is to consider the full impedance curve, not just a static number. Maybe that is where "all other matters" are not equal.

That is certainly part of it! There is a reason some speakers are considered 'difficult loads' and that is never a good thing as far as the amp is concerned.

The OP was about tube amps that can drive ML ESLs. The issue here is that ML has been really trying hard to make their speakers work better with transistors, which is not easy to do, because ESLs want constant power and transistors are constant voltage (see http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php.

I'm pretty sure I explained all this earlier- a lot earlier:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1394129996&openflup&11&4#11

But if you have a set of ZEROs, its pretty easy, then its just about whether you have enough power, not whether the amp is comfortable with the load. Seems to me 60 watts will make most MLs play reasonably well.
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