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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
mapman's avatar
mapman
22,510 posts
 
YEs, but realize that tube amps in general will distort even more than SS amps into 4 ohms, so if 4 ohms is part of teh puzzle, the answer is clear.

Any good amp, SS or otherwise can drive an easy load easier.

SO you have to look at all the pieces of each puzzle together in the right way , not take one piece from one puzzle and try to insert it into the the other and then blame it for not working.

Likewise, there is always good, better and best in any case/scenario. Its important to understand impedance and phase related issues in order to assemble the right pieces. Then you can assess system/puzzle A versus B however one likes, but better to look at the overall results than the relative deficiencies or strengths of any one element of design.
georgehifi's avatar
georgehifi
10,312 posts
 
03-27-14: Atmasphere: do so despite George's remonstrations

Are you kidding, far from pleading with you Ralph.

I agree that an Autoformer is a great (pseudo) bandaid fix for whatever amp that cannot drive a speaker that is not a good match, because of it's inability to deliver current/wattage or is working out of it's SOA (safe operating area) A FAR BETTER FIX IS TO CHANGE THE AMP/S OR SPEAKERS!

You state that even a good solid state amp will measure less distortion on it's output from using a Zero Autoformer into a 4ohm load compared to 8ohm.

Yes I agree that with the Autoformer even a good solid state amp will measure slightly less distortion at it's output terminals at 4ohms (this is not to say it's out of it's SOA)
But it's what happens after the Autoformer (things like phase shifts, damping factor etc) that is far more detrimental to the sound than the slight increase in distortion before it without the Autoformer.

EG: What one would basically do to a good amp say like a Pass Labs, Krell, Gryphone or similar amp by sticking an Autoformer on it, is to turn it into the solid state series MacIntosh's that also use a type of Autoformer on their outputs, but without the benifits of using them within the amps feedback loop, to keep the (damping factor, phase shifts, etc) in check.

Cheers George
unsound
7,336 posts
 
There are many, many speaker cables to choose from. I'm confident that one would find many (if not most) will work just fine with a 4 Ohm load speaker.
pryso
1,955 posts
 
This is for Ralph, since I'm quoting him. But any others are welcome to jump on it as well.

"I am not stating that 4 ohm speakers are bad speakers. I am stating that any amplifier driving them will sound harsher and less detailed as opposed to the same amplifier driving the same speaker that was 8 ohms, were all other matters to be equal."

I admit my knowledge of electronics is very limited, but this raises a question for me. Is the singular impedance rating of any speaker worthwhile or even all that important? Or is a better question what is the impedance plot across a speaker's response range?

I ask this because for many years I owned Duntech speakers which were rated at 4 ohms. However, reviewing Duntech's impedance plot, it dipped close to 2.5 ohms at two points, the most troublesome being between 60 and 80 Hz as I recall. Considering the power called for at that frequency range and the dip below 3 ohms, well, not ever amp rated to drive a 4 ohm load got off easy!

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.
georgehifi's avatar
georgehifi
10,312 posts
 
I do not manufacture amps that may or may not need the Zero in circuit, so there are no ulterior motives for me to hide or protect.
I just don't like to see blanket statements like the Zero will improve all amplifiers regardless of topology.
They have their place in that they make an amp that has trouble to drive certain loads with relative ease, able to do so.
But it is not the definitive answer, it is a bandaid fix, changing the amp/s or speakers is the way to go in these cases.

Here is another point made from Dick Osher's review of the Zero Autoformer that was conveniently left out of the link to the excerpt of the review.

"T-Rex 300B SET, a DIY design project in the works (still unpublished) using Plitron output transformers with only 8-ohm taps, and the Lowther DX4 BassZilla - a 97dB.
At his point, it became clear that although bass lines still benefited from the ZERO, overall the T-Rex - BassZilla interface sounded better with the ZERO out of the way."
"Small, but noticeable errors of commission crept in. Soundstage transparency diminished, which reduced the music's intimacy. Microdynamics now sounded slightly over damped, releasing some of the music's tension. The midrange, which for me paints a window onto the music's soul, became slightly cloudier. On balance, I would rather give up 20% of bass definition for a 10% increase in midrange clarity.":

As you can read the 300B set amp (and others eg OTL's) not known for good drive current, was improved in the bass area with the Zero, but the midrange diminished by 10%
The same 10% detriment will happen to the midrange using a Zero with a good solid state amp or powerful tube amp that have no problem in delivering good bass without the Zero.
The word Dick Olsher used "cloudy" in reference to the midrange is also what I heard in my system with the Zero's attached to a good SS amp that could drive the speakers with no problems, and as well as the bass tightness and drive diminished just as much with it in.

Cheers George
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