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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
 
Generally yes ... reason ... there's much less energy called for in the high frequencies. If your music source required the amp to push 100 watts of power into the tweeter, not sure what would blow first ... your ears or the tweeter.

Most of the power demands placed on an amp are in the bass/low midrange. Much less power demands in the upper end.
georgehifi's avatar
georgehifi
10,312 posts
 

Once again from the Martin Logan website. They should know their own speakers.

"Quote:
However, it is important that the amplifier be stable operating into varying impedance loads: an ideally stable amplifier will typically be able to deliver nearly twice its rated 8 Ohm wattage into 4 Ohms, and should again increase into 2 Ohms." Quote:

Cheers George
bifwynne
2,206 posts
 
George, that's a pretty clear clue that ML advises that the owner should use a rock stable SS amp. I don't know how low the impedance gets ... but that is a factor to consider when picking an amp.

This issue has come up before .. possibly in this thread. I'm a tube guy, so I'll let the SS guys weight in. I seem to recall that Ralph thinks Zeros can help in these situations. Never used em' so I stop here.

georgehifi's avatar
georgehifi
10,312 posts
 

The fact is they want an amp that are stable and also that can double it's wattage from 8ohms down to 4 ohms and yet still increase even to 2ohms, (which means an amp that can do good current)
This means that if an amp cannot do this, then at the low 1ohms or 2ohms that their (ML) speakers present to an amp, then that amp will then start to behave like a tone control, and not stay flat in frequency response over the entire impedance range of speaker it's driving.

As simulated speaker load graphs will show you of amps that cannot deliver current at those low loads, therefore their frequency response will not be flat.

All you have to do is look at Stereophile speaker simulated load graphs of tube amps especially to see that they cannot give a flat frequency response into those types of loads, especially ones that dip down to 1ohms.
If you need proof I will post links for you to see what happens, but I think you should go and look for yourself.

Cheers George
almarg's avatar
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almarg
9,670 posts
 
Great posts by Bruce (Bifwynne), with which I fully concur.
09-13-15: Georgelofi
... amps that cannot deliver current at those low loads ... cannot give a flat frequency response into those types of loads, especially ones that dip down to 1ohms.
This is true, but I would emphasize the word "into." The frequency response characteristics of the signal at the input terminals of a speaker that will result in flat frequency response in the acoustic output of the speaker will depend on the design of the particular speaker. As Bruce said, it is "important to know whether the ESL was voiced to be driven by a SS or tube amp."

And in that regard it is worth noting that the Quad ESL57 was designed before solid state amps existed. Although admittedly, as I believe you (George) mentioned earlier in this thread or in another similar thread, the vintage Mark Levinson ML-2 solid state amp in particular, rated at only 25 watts or thereabouts into 8 ohms but capable of supplying huge amounts of current into low impedances, is considered by many to have been a good match for the ESL57. While at the same time that speaker has been and still is used with tube amplification by many audiophiles.

Regards,
-- Al
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