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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
unsound
7,327 posts
 
"...IOW the ML ESLs are a low impedance Power Paradigm loudspeaker..."
Perhaps I'm missing something here, but do these graphs seem to suggest something else?
http://www.stereophile.com/reference/810/index.html
bifwynne
2,206 posts
 
Unsound ... I found that same point confusing too, especially in light of ML's recommendation to use an amp that increases power as speaker impedance drops. That sounds like a Voltage Paradigm/SS amp. But our other "enthusiastic" techie members wore me out. Glad you picked up on that point too.
almarg's avatar
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almarg
9,670 posts
 
Unsound and Bruce, as you may have noted TJN's article that Unsound referenced addresses how impedance interactions affect frequency response at the speaker's INPUT terminals. In itself that says nothing about what the speaker's acoustic output will be like in response to those inputs.

I have no knowledge as to whether optimal frequency response of the acoustic output of the Martin-Logan Aerius would result from a flat frequency response at its input, or from a frequency response at its input that is non-flat in some manner. But see the comments in my previous post regarding the Quad ESL-57, and take a look at its impedance curve that I referenced.

Best regards,
-- Al
jandidden
8 posts
 
So, to recap, what did we learn:

- output impedance of a 'box' is *defined* as the change in output voltage divided by the current change that caused the voltage variation;
- nfb makes the output voltage change smaller for the same current change, so *by definition* lowers the output impedance.

We also saw that nfb does not change the 'internal' output impedance of an amp - nfb operates strictly outside the amp proper. Also, we saw that (to a first order) this change in output impedance due to nfb does not change the amps output capability. Lowering the output impedance towards zero does not all of a sudden produce an amp that can deliver gobs of power in very small loads. The as-designed amp capability does not change.

A corollary we did not discuss but should be quite obvious: since damping factor is *defined* as load impedance divided by output impedance, output impedance drop due to nfb consequently increases damping factor in the same measure.

This was a good exchange!
wrm57
1,034 posts
 
Yes, fascinating thread, even for a non-techie like me.

If I may ask a corollary question: is there a relatively simple rule of thumb to determine whether a speaker might prefer a Power Paradigm or Voltage Paradigm amp?
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