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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
hvowell
13 posts
 
This is all well beyond my understanding and wondering can someone comment on a question concerning the voltage vs power model? I believe I read two, perhaps more, points of view?

Concerning an ESL such as the Quad "57" referenced earlier with a SS amp "doubling" the amps output as the impedance is halved (assume)

25W into 8ohms
50W into 4ohms
100W into 2ohms

would not the output be also "halved" as the impedance rises above 8ohms

12.5W into 16ohms
6.25W into 32ohms

If I understand correctly than, for the Quad ESL this means only 6.25W/12.5W in the lower frequencies while 100W into the higher frequencies?

Now is the reason this type of amp works is (assuming the speaker has a sensitivity (SPL) of 85db/1W into 8 ohms)

.25W into 32ohms = 85db
.50W into 16ohms = 85db
1W inot 8 ohms = 85db
2W into 4 ohms = 85db
4W into 2 ohms = 85db

so the SPL remains constant into all impedances?

Thank you everyone for all the previous information, so very informative!

Lee

zd542
5,339 posts
 
"If I understand correctly than, for the Quad ESL this means only 6.25W/12.5W in the lower frequencies while 100W into the higher frequencies?"

No. Its the opposite.

If I understand correctly than, for the Quad ESL this means 100 watts in the lower frequencies while 6.25W/12.5W into the higher frequencies?"
hvowell
13 posts
 
The quad has an impedance in excess of 32 ohms under 100HZ, with just under 2ohms impedance at about 10KHZ.

Lee
zd542
5,339 posts
 
That seems to be the opposite of what it is for most other speakers. Maybe there's something unique about that particular design.
bifwynne
2,206 posts
 
Going out on a limb here by getting technical than I should. But I recall reading posts from some our tech members that described the "common" ESL impedance function to be like capacitor. That is high impedance at low frequencies and low impedance (sometimes very low) at high frequencies. Indeed, some of the posts said that only amps that are stable driving such loads need apply.

I think another important question to think about is whether the ESLs were voiced to be driven by a SS or tube amp. As Ralph Karsten (Atmasphere) has explained in his white paper, most SS amps operate under the Voltage Paradigm, i.e., these amps have a very low output impedance and maintain constant output voltage. Under this model, power (i.e., watts) delivered to the speaker will inversely vary with the speaker's impedance, i.e., less watts at high impedances; more watts at low impedances.

By contrast, many tube amp have higher output impedances and operate under the Power Paradigm. In such cases, power (watts) will not vary as much with changes in speaker impedances.

The main point is that as long as the amp is operating within its safe operating range, it's more important to know whether the ESL was voiced to be driven by a SS or tube amp.

Btw, I think Ralph has suggested using ZERO autoformers to simulate higher speaker impedance. The theory is that Zeros can help amps manage the very low speaker impedances presented by some ESLs at high frequencies.
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