OTL Tube Amp for Maggie 3.6?

We've got a lot of customers that like the combination so it must work...

Realdeal, that's a logical question, but it has a logical answer. See the quote in my post above dated 3-25-11.

Also, of course, the low impedance and low efficiency of a Maggie would seem likely to be problematical, to say the least, for the typical low powered SET.

Regards,
-- Al

OTL,,you already avoided output transformer?and why in the world you will put a ZERO in your output?You better off with an SE

Ooops. Okay, 6k and 6 figures are vastly different meanings regarding spending money. Heck, if I had enough money to splurge on a beefy OTL, I would be tempted to evaluate the MA2 or MA3 with my B&W 800'. Perhaps one day when we return to the United States from our European vacation. You don't offer 30 day trials to Germany by any chance? How about military discounts? Just sayin:).

You can see the equipment I am using by looking at my system profile.

Ciao,
Audioquest4life

Audioquest4life, there is nothing about 6K- but he did say something about trying to keep it under 6 *figures* :)

If you are trying to stay below 6K, then perhaps you may need to change your mindset of using OTL's with a pair of Maggie 3.6's. For a beefy enough OTL to create the dynamic swings, and loudness to make these particular speakers sing and swing, I think you are going to be out of your budget. A few suggestions made here for OTL's seem to be way out of your price range, and the few that are close, may not supply all of the power you require. I do not know about you, but I like to play my music at real volumes, not as background music, so having the ability to play louder is important to me, along with the ability to explode dynamically when necessary.

Generally speaking, most users on the forum suggest matching amps to speakers, the Maggies are no exception. The trend in the forums for Maggies seem to suggest high current and beefy power supplies, something you are not going to get with smaller wattage OTL's. I am sure that the Zero's may aid in some cases regarding matching impedance and ohms, something I would like to experiment with, but, how do you get around for the lack of power and or reserves necessary to make music come alive with small power supplies?

If I were you, I would experiment not just with OTL, but, with other options, such as hybrid and push pull.

If you are dead set on an OTL solution, then please evaluate and provide us with your findings regarding dynamic range, explosive power, and how loud you could play without sound degradation before the amp ran out of power.

It would be interesting to hear some feedback of users using lower watt OTL’s with this particular speaker and how loud they play them.

Ciao,
Audioquest4life

Glad to see someone going down this road. I ran 3.6's with my VZN 160's. I have very fond memories of it. I had the OTL's driving them full range and even bi-amped them with various amps for just the bass panel, including the H2O ice audio class d amp. My recollection is that the biamping of the 3.6's in this manner was overkill for that speaker. I much preferred running the 3.6 at full range and augmenting that set up with a sub. As a Maggie enthusiast, I also augmented the 3.6 with Tympani bass panels (single pair and double)driven with the H2O. That was a good system for a while. I always ran the OTL's with the zeros. I don't think I ever turned the volume past 12 o'clock. OTL and ribbons are a glorious sound. But for the lack of imaging, I'd still have that system.

03-25-11: Rushton
While an Atma-Sphere MA-1 certainly works with the Magnepan 3.6 speakers, particularly in smaller rooms and at lower volumes, these speakers absolutely shine when driven by the Atma-Sphere MA-2. A marvelous combination.
Rushton (Reviews | Threads | Answers | This Thread)

I will give a hearty second to Rushton's suggestion. He and I listened to his MA-2s on my 3.6Rs and it was a marvelous combination in a medium sized room (16.5 x 23)

there's a lot of hearsay in this thread, so I won't refrain from adding mine:

A good friend of mine has successfully used Maggies with two ZH270 by David Berning - nowadays you might want to go with the Quadrature Z, that would be heaven!

Said friend later changed to Ambience speakers, but the Bernings are still there..

Response34, I had a push pull amp from McAlister Audio back in 2005 (believe it was called something 140, 70 watts/channel). Problem with his amp was very poor build quality, although the sound was good. The output transformers had laminations missing that was filled in with small pieces of metal and was caked with this greenish stuff that looked like it was oxidized from years of use. The soldering job was by far the worst I have ever seen, looked like a 10 year old had at it. Speaker binding posts were completely loose when it came to me. Fortunately it cost only around $1600 at the time. I was not the first who had issues with build quality of his amps. I sold it after less than 1 year of use for about $700, but it broke down less than a week after sale. He is now charging close to $9000 for his OTL amp. The outside cosmetics has been upgraded, but I hope he has vastly improved his build quality and reliability for this amount of money. He can take a lesson from the build quality and reliability of Atma-Sphere amps. BTW I have no financial or personal affiliation with Atma-Sphere.

Dear Ahendler, I cannot tell whether anyone else has already pointed this out to you. You concede that the Zero is an autoformer (not a transformer) and then you bemoan the idea of using one because you would be sticking a "transformer" in the signal path. So, an autoformer is different from a transformer: (1) The audio signal does not have to be induced into secondary windings from primary windings; no hysteresis; (2) The audio signal does not have to traverse a huge coil of wire; (3) Autotransformers therefore have much wider bandwidth and much lower distortion than even a fine quality output transformer. I am not saying that there is no penalty associated with use of a Zero; you need to listen for yourself to determine that. But otherwise, like Ralph says, you need a herd of output tubes to make an OTL work well into a Maggie, no matter how linear the load may be.

There are two ways to make an OTL work with 4 ohms really efficiently.

The first is to make it so big that 4 ohms is no worries (our MA-2 and MA-3 are examples of that- the MA-2 makes its maximum power into 5 ohms and the MA-3 makes its maximum power into 3 ohms). The second way is to use a set of ZEROs (http://www.zeroimpedance.com)

If you are planning to bi-amplify the latter method will allow you to use a smaller amplifier, which may well be just fine if it is only handling higher frequencies. The ZEROs can be a very effective solution for using smaller tube amplifiers on lower impedance loads.

If anyone knows if it would be better if an OTL tube amp were designed for 3 ohms vs 4 for a Maggie 3.6/3.7 let us know.

Other than that, they seem very suited for what planar speakers do, especially in terms of the fact that planar speakers are so transparent, and then the OTL aspect maintains that through the system.

Another question - because where money is an issue in my systems, I wonder what people would think about matching a relatively cheap ClassD amp, like the Rotel 500 watt ICE in an active bi-amp setting.

I've heard that with active bi-amping amp-matching is important. Remember that the 3.6/3.7s cross over at 200 - 250 Hz, so we are talking low frequencies where quality matters less because of the physics.

Given the high cost of OTL, this would be an interesting option:

24/96 source
Good DAC and Pre
Bryston X-over
Rotel RB-1572 (although I'd love to use the ICE1000 vs 500, they stopped making theirs, I'll poke around for another 1000 module)
Atmasphere MA1 or VZN-160 or The Beast
Maggie 3.6

The OTL amp still consists of most of the cost of all of this, unless one gets The Beast and builds it themselves.

Note that going active bi-amp makes the high-frequency amp at least double in effective power by isolating the range of frequencies it has to deal with at once.

I have to look into The Beast more. The other OTL amps are out of my range at the power required to drive Maggies, for more efficient speakers I'd be there in seconds.

Has anyone heard it recently? Does it really sound as good (or nearly as good, I'm sure it isn't as good) as any of the other OTLs, or is it much more limited in quality? Is it compromised enough that its doesn't that the OTL sound anymore?

First as a disclaimer - I am an audio dealer and manufacturer.

One of my associates run a pair of King Sound "King II" panel speakers with the new McAlister Audio OTL 195 mono bloc tube amps and has no problem with these difficult speakers.

A set of power tubes for a pair of MA-3s is $2000.

Wendal Diller told me once that the best he ever heard the MG-20.1s was with a set of MA-2s. Certainly MA-2s have no problem with 3.6s and the like! Years ago a friend of mine ran Tympany 4s with MA-2s- that worked really well too. IMO the trick is to keep the speaker cables short.

You might need that just for tubes on the MA-3:)

The MA 3s looks good on power, but I'm trying to stay under 6 figures.

03-25-11: Ahendler
I know that the Zeros are an autotransformer but isn't the big reason of the sound of otl's is because they do not have an output transformer. Now we stick one back into the equation. Seems counter intuitive.

Yes, it does seem counter-intuitive, but the FAQ on the Zero's has what seems to be good rationale:

What is the difference between the ZEROs autoformer and a typical tube amplifier's transformer?

The ZEROs have a few advantages over "typical" tube amp transformers:

A) The music comes out on the same winding wire that it goes in on so the music does not have to pass from a primary winding to a secondary winding.

B) There is no DC current to contend with. When a transformer is made to accommodate a DC field, its audio transparence is compromised.

C) The impedance ratio is very small (16 ohms to 4 ohms, compared to a few thousand ohms to 4 ohms). This simply means that it is much easier to achieve things like, frequency response extremes, than with a "typical" tube amp transformer. The ZEROs sport a frequence response of 2 Hz to 2 MHz.

Regards,
-- Al

I mentioned so many things, just to say, lets keep this thread on the topic of OTL amps as applied to Maggie 3.6 or 3.7s (or 10s if there is experience with that out there).

4est - I actually love the Aleph 5 on them. One thing I was thinking of doing is adding a Class D (because the xover point on the 3.6 is so low so the negatives don't come into play - 200 hz) and doing active crossover, and keeping the Aleph 5 for the high end. It sounds quite amazing an Jazz vocals and lots of stuff. The aleph 5 in a lot of ways is as close as you can get to the smoothness of a tube amp with solid-state, but still get higher watts at lower impedances, and the ease of a solid-state.

You are right, however, there are tradeoffs in everything. I have an old Luxman in my garage from the 80s with something like 800 watts at 4 ohms. It is a very different experience, and has plenty of PRAT. That is why I was thinking of adding a Class D device for the bass panel.

But in reading about certain electrostatics that are crazy big-buck, it seems that OTL tube has been considered the 'best' amp that exists (I know, I know...). Just expensive. So seeing what can be done, and as I'm a tinkerer I don't mind putting one together myself and seeing what happens, the Beast seems like an option.

Also, the idea behind using the Beast is that it might be powerful enough as a single amp to just stick with passive xover. I don't see a lot of high power OTL tube amps for reasonable amounts of money. I have a modded passive xover, and also I have a 3.6 late-model refresh xover that basically no one knows about, but anyhow it sounds great. So sticking with passive is fine.

My other options are:

XRV1 with Class D on low end (maybe even NuForce 8.5)

OTL Tube

Pass 60.5 or 350.5

magfan - OTL does something that can't otherwise be done. There is magic there. If you can hear them locally, find some Joule Electra dealer and prepare to be stunned... Also their pre-amps are no slouch :). But I'm trying to find a cheaper way to get the Joule Electra sound.

Atmasphere - I'm not against that at all, although per Ahendler's comment, I'd really like to do it without Zero's.

I guess another option is XVR1 or Bryston with lower power OTL on top end and NuForce 8.5 or other ClassD on lower end. Honestly I suspect that Rotel would be find given the xover point. That all can start getting pretty expensive, though. Bryston xover and Rotel ClassD would help make it affordable.

Atmasphere - would it be hard to have a MA-1 or MA-2 that is made for lower impedance loads? I see this comment on your website: "The MA-2 in particular is noted for its superior performance on Sound Lab, Wilson Audio, JM Labs, Magnaplanar and Avalon loudspeakers (90% of all MA-2s built are running on these speakers)" but still - not knowing electronic details, instead of a 4-ohm switch, maybe a 3-Ohm switch? I don't know if it would in the end make much of a difference, but it sounds like for OTL it might be an important difference. Of course you'd want to check the 3.7 these days and see if it is 3.25 Ohms like 3.6 (see next paragraph).

From 3 kHz to 50 kHz the impedance is around 3.25 Ohms. From 10 Hz to 1 kHz it is more around 5. There is some funny stuff inbetween, it peaks very high briefly.

Phase angle is 0 from 10 Hz to 1 kHz and linearly moves up from -22.5 to 40 between 2 kHz and 50 kHz. Stops at maybe 15 deg at 20 kHz?

If I went with Bryston xover and Rotel ClassD I could use the Aleph5 for another several years and then add an OTL for top end later. That actually could make a lot of sense.

And in terms of going from A to B I could even use the 800 watts in my garage in the short term, so that would just mean getting the Bryston xover for now...

But I really like the idea of OTL. I'm obviously not sure if OTL on top end and ClassD on low end may be too different of a sound, if speed is different, if somehow it would be too different and people could tell.

I know that the Zeros are an autotransformer but isn't the big reason of the sound of otl's is because they do not have an output transformer. Now we stick one back into the equation. Seems conter intuitive

Ah, to have MA 2s...

I can see how with the Zeros it would work.

While an Atma-Sphere MA-1 certainly works with the Magnepan 3.6 speakers, particularly in smaller rooms and at lower volumes, these speakers absolutely shine when driven by the Atma-Sphere MA-2. A marvelous combination.

Even MORE important than sensitivity is the phase angle of the load.
That is to say....how capactive or inductive the speaker is.

Find the Stereophile test of the speaker. The test is in their archives and will have an impedance / phase graph against frequency.
Read the recommendation of stereophile's testers and take in account your experience and needs.
Now, I don't know specifically about OTL, but normal, transformer'd tube amps do not like capactive loads....even if the impedance were fairly flat.

We've had a lot of people use our MA-1s on the 3.6 to good effect. In fact the moderator of MUG (Magnaplanar User's Group) emailed me a few years back saying that the MA-1 was the best amp for that speaker.

However 4est makes a good point about power- in the 3.6, the sensitivity is 86 db. This spec is misleading since the speaker is 4 ohms and it is a line source. I think it is more valuable to know the efficiency of the speaker since that is a power rating and tube amps make power. The speaker is 4 ohms, causing the *efficiency* to be 3 db less. But the speaker is a line source so you add 6 db to that. IOW, the speaker is about 89 db 1 watt 1 meter. An amplifier that makes around 100 watts might be run out of gas at higher volumes, but a lot depends on the room and your listening taste.

Some OTLs cannot handle the load even though they make the power; a popular and effective solution is to use a set of ZEROs (http://www.zeroimpedance.com). Take it from me on this one- the use of such does not obviate the 'OTL quality' of the amp. With our MA-1 it is hard to say if the ZERO would help or not, I suspect you would have to try it and see.

How do you feel about your Aleph 5 on them? I cannot see as how the Beast would work, or really any OTL for that manner. It is spec'd at 160 into 8 ohm, and 110 into 4 ohm. To me that indicates that it will not mate well with Magnepan 1.6s as they seem to like current. I have attempted to use an Aleph 5, and didn't like it on them- lacked PRaT. I attempted several 100 w tube amps and had the same issue. These were not wimpy cheap amps either. It always reminded me of the old days when I first go into tubes. I was trying to run MG 1s with Dynaco ST70s or Mark VIs. There was a hint of greatness, but I was always left wanting. It was not until I installed my Parasound JC 1s (400w/800w) that they awoke. I do not listen loudly either. It is about dynamics and low end control.

I am sure that others are sure to disagree...