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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
tomcy6's avatar
tomcy6
2,589 posts
 
I think that ML designed their current line to be used with either tube or ss amps, the choice being the user's.

Robert Deutsch spoke with Peter Soderberg of ML who told him that of the systems he has set up using tube amps, about half prefer the 4 ohm terminals and half prefer the 8 ohm terminals. So obviously ML approves of using tube amps with their speakers. And with a max recommended amp power of 500 wpc, they also approve of ss amps.

The measurements in the review show some roll off above 5000khz but we all know that a flat frequency response does not mean a good sounding speaker.

In my opinion, these speakers are not beasts to drive and I think you would agree if you listened to them.
bifwynne
2,206 posts
 
Tom, if you read my posts, I framed my question by referring to those tube amps having a "high'ish" output impedance (say 3 or 4, or more ohms).

By contrast, some amps like my ARC Ref 150, have a "low'ish" output impedance, possibly because they use negative feedback. Specifically, the output impedances off my amp's 4 and 8 ohms taps is about .5'ish and .6'ish ohms, respectively. As a consequence, the Ref 150's output voltage regulation is pretty tight: about +/- .4 db and +/- .8 db off the 4 and 8 ohm taps, respectively. So in effect, tube amps that have a low'ish output impedance function somewhat like a low impedance SS amp -- constant voltage source.

I mention all of this because you say in your last post that "ML approves of using tube amps with their speakers." Well ... that may be. But then there are tube amps, ... and then there are tube amps.

Regards,

Bruce
bifwynne
2,206 posts
 
Quick postscript: my posts are not just academic. The OP is asking about matching a tube amp with ML ESLs. My comments are trying to focus attention on whether the ML ESLs in question should be driven by a low impedance amp that acts as a constant voltage source, i.e., a typical SS amp or a low impedance tube amp.

As I said above, "there are tube amps, ... and then there are tube amps." My somewhat tongue-in-cheek point is that if the ML ESLs were designed to be driven by a low impedance amp, then the OP should be cognizant about the output impedance of the tube amp he has in mind. The consequence of using a "high'ish" output impedance tube amp like an Atmasphere OTL is that the sonic colorations may result in augmented bass and shelved treble. Of course ... even a low impedance tube amp may need some serious current capabilities, even if it performs SS-like. Consider the EPDR article and its reference to SOA.

By the way, as I also mentioned, while ZEROs may raise the apparent across the board impedance load presented to the amp (SS or tube), I am dubious that the device will smooth out the sonic presenation of the MLs if the wrong type of amp is used. Perhaps Ralph or one of the other tech members can speak to how much SPL variation will result if the "wrong" type of amp is used. Perhaps, for discussion purposes, we should assume the MLs were designed to be driven by a SS "constant voltage paradigm" amp and the "wrong" type of amp is a Power Paradigm amp.

I surmise that if the tech members respond, we will all gain a better understanding of whether one should drive MLs with a Power Paradigm tube amp if they were voiced to be driven by a SS/Constant Voltage Paradigm amp.
tomcy6's avatar
tomcy6
2,589 posts
 
Bifwynne and everyone else,

Thanks for your efforts to clear up the technical issues involved.
georgehifi's avatar
georgehifi
10,312 posts
 
03-29-14: Tomcy6
I think that ML designed their current line to be used with either tube or ss amps, the choice being the user's.

Yet if you Google images for previous big HiFi shows, and look at specific Martin Logan rooms demo's, as far as I saw nearly evey demo by ML was done with big SS amps like Krell and such.

The only ones I saw driven by tubes were not in a Martin Logan rooms, but were in an tube amp manufacturers rooms, who were using ML powered bass hybrids for their speakers.

Cheers George
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