In general its frequently thought tubes are a bad amp for electrostatic speakers. Something to do with current delivery that low ohm speakers require. On the other hand there are some tube amps that can do the job. Perhaps a different combination would suite your needs better.
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The Logans are rated at 4 ohms. They might be conservitally be rated at 4ohm, but they do dip to 1ohm in the highs, with "may" see a dulling/recessing of the highs with many tube amps, unless like the Roger Modjeski RM200 Ram Tube amps, that have 1, 2, 4, 8ohm transformer taps, then enough watts become an issue. Because the lower you go in "tap ohmage" the "lower the watts become" also, so a 100w at 8ohm tube amp may become only 25w at 2ohm. Cheers George |
In general its frequently thought tubes are a bad amp for electrostatic speakers. I never heard this before. Perhaps this is true for amps with rather output transformers. But any speaker that dips down to 2 or even 1 ohm is going to cause a lot of amplifiers, tube or SS some serious pain. I have run Sound Lab A1's for 13+ years, and these too dip to nearly 1ohm at the higher frequencies. The 220w Wolcott tube amps drove these speakers incredibly well. And then I changed to CAT JL-3 amps, 150w rated, which also do not have multiple output taps, and the result is stunning. Make a call to ML as well as VTL to learn if a particular VTL amp would be a good match for the 11A's. |
@georgehifi has given you a good lead in the Music Reference RM-200 Mk.2. It is the only tube power amp I know of that puts out 100 watts at both 8 ohms and 4 ohms (do the McIntosh amps also?). The common wisdom used to be that OTL amps were a great match for ESL’s, and the Futterman amps were often paired with old Quads, single and stacked. Lots of Atma-Sphere amps on Quads and SoundLabs as well. MR’s Roger Modjeski, a very opinionated designer/builder, disagrees (and has no axe to grind; he builds OTL’s himself). If interested, go to the MR website for more details, and read Michael Fremer’s review of both the original and Mk.2 versions of the amp in Stereophile (and equally important, John Atkinson’s bench test reports). |
Oops, neglected to include the matter of tube amp output impedance. Many tube amps have a high enough figure to cause considerable roll-off or boost at either the bottom or top (or both) of the audible frequency range when paired with speakers themselves having very low or high impedances at some frequencies, ESLs being exhibit number one. |
bdp24 and georgehifi are absolutely correct. You may want to read Roger Sanders white papers to get a contrasting view. I personally am not a big fan of using tube amps on ESLs which like jafox I have been running for decades. One transformer is bad enough. Two transformers is really uncomfortable for my brain. Now OTLs get rid of the second transformer and Atma-Sphere amps have a storied history with SoundLabs but I have not heard this combo yet so I can not speak from personal experience. But I have had numerous amps in my system and as a rule Class A SS amps fair the best the two outliers being The JC-1 and strapped AHB2s. I also cross to subwoofers at 125 Hz so the ultimate low bass performance is not an issue for me. You also cross to woofers I think it is somewhere around 250 Hz but don't quote me on that. Biamping would be a consideration but that still does not negate the issue with low impedance at high frequencies. Trick: put a 1 ohm 200 watt resister in series on the + side of the speaker. This will not decrease the efficiency of the speaker all that much and frequently makes the amp more comfortable with the high end. Digikey has them. These are not little devices. They are mounted in 3 inch X 2 inch heat sinks. I always do this if I have trouble with amps overheating and it solves the problem 100% of the time. |
The following may appear to contradict what I said about Modjeski's opinion of OTL's paired with ESL's: Roger is making his own ESL loudspeaker (which includes an 8" woofer for each side; another pair can be added, of course). But dig this: he is also offering it with a direct-drive OTL amp for extra $. "Direct-drive"? The mono OTL for each speaker has no output transformer, of course, but the ESL has no input transformer. The OTL output tubes drive the ESL panels directly! Modjeski worked for Harold Beveridge, who had Roger redesign the power amps that were integral to his ESL, also direct-drive. So this is not new to Roger, but it sure is unique. It takes a lot of engineering knowhow to pull off, involving the disciplines of power amps, tubes, transformers, ESL design and construction, and extremely high (lethal) voltages. No kids or pets allowed in the room ;-) . |
The answer could very well depend on which Manley amp is being considered. For example the Manley Neo-Classic 250 has a specified output impedance in the vicinity of 0.5 ohms (John Atkinson’s measurements reported in Stereophile were 0.6 and 0.7 ohms for triode and tetrode mode, respectively). Those are extremely low numbers for a tube amp and suggest that the effects on tonal balance resulting from the interaction of that output impedance and the speaker’s impedance vs. frequency characteristics will be relatively solid state-like. (The RM-200 mentioned by George and bdp24, by the way, has a comparably low output impedance on its lower impedance output taps). On the other hand the Snapper has a specified output impedance of 1.5 ohms, which everything else being equal will result in a less extended upper treble, compared to the Neo-Classic 250.
I have no idea which of those presentations is likely to be preferable with this particular speaker, or how desirable either presentation might be, or how problematical the deviation from the recommended 5 ohm load might be for the amplifier, but as Jafox suggested it would be a good idea to contact the manufacturers and solicit their thoughts about the specific pairing. If you already haven’t, I would also try to find user comments about amplification others have used with the ESL 11A or with its larger brethren in that series (the 13A and 15A). I would not extrapolate much if anything from generalities about ESLs, or from experiences involving other makes of ESLs, as in most cases the Martin Logans are different animals than other ESLs in terms of impedance characteristics, inclusion of powered woofers, and other respects.
Good luck. Regards,
-- Al
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this is the full spec sheet for the Manley Neo-Classic 500 mono blocks. some of which I do not understand. - LL-TUBE monoblock design 10 x KT90EH Electro-Harmonix Russian output tubes
- High current double 12BH7EH driver stage
- Tungsol 12AT7 large plate input tube
- BALANCED & UNBALANCED inputs
- MUTE switch
- TRIODE / Ultra-Linear switching
- SOFT-START/ EVER-WARM standby mode
- MANLEY Precision output transformer
- Factory set for 5 Ohms nominal
- Front panel bias measurement and adjust (hiding under the black insert)
- Large filter / reservoir capacitors 3800uF x 2
- Angled rear of chassis provides for easy connections
- WBT binding posts
- Input sensitivity: 1V
- Gain: 32dB tetrode; 30dB in triode
- Input Impedance RCA: 116 kOhm @ 1KHz
- Input Impedance XLR: 270 kOhm @ 1KHz; 20 kOhms @ 20KHz; 38 kOhm @ 20Hz
- Noise Floor: Tetrode: -67dB; Triode -65dB typical
- S/N Ratio: -80 dB
- Dynamic Range: 96dB
- FLAT frequency response: 10 Hz - 30 KHz continuous
- Power Consumption: 30 Watts in "EVER-WARM"
- Full power (tetrode): 500W
- Full power (triode): 275W
- Factory set for 100V, 120V or 220-240VAC operation for original destination country's mains voltage.
- Operating Mains Voltage changeable with power transformer re-wiring and fuse value change.
- Mains Voltage Frequency:
- Dims: W=19", D=13", H=9"
- Shipping weight: 82 lbs. each
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I was about to provide the same counsel as mijostyn above, and am gratified to read it here before I posted it. Roger Sanders excellent white paper on tubes vs transisters explains a lot.
My .02 is that you probably can pair Manleys with the Martin Logans, but at what cost? Which model in the range? I think you might find the Magtech equal or superior, at a very reasonable cost. |
Two transformers is really uncomfortable for my brain. Why the two transformer phobia here? Years ago, I auditioned a pair of Sound Lab U1 speakers with three amps: Atmasphere MA1, CAT JL-2 and Parasound JC1. First up was the JC1 and the sound was boring. Had this been the only amp I heard that day, I never would have bothered again with the SL speakers. Next up was MA1 and the sound was truly beautiful. Dimensionality and harmonic structures was truly incredible. The JC1's were absolutely broken in comparison. Last was the JL-2 which did not have quite the lushness of the MA1 but with the CAT came far greater dynamic contrasts and a bigger bolder presentation. The choice between the 2 tube amps was not easy, as both had excellent tonal coherency with the MA1 just having a little more presence in the lower mids. But I went with the CAT as it controlled the SL speakers with incredible authority and I knew I could get some of that MA1 "magic" back with the right preamp and tube rolling efforts. And ultimately I did with Aesthetix and later Aria preamps. So the whole notion that transformers are "bad" was clearly disproven to me that day. I still suspect that the VTL or Manley amps might be outstanding here as they too bring on an outstanding 3D quality that might work beautifully with the ML's. If you want to consider SS amps that won't break your budget, look for a good deal on a BAT VK 600SE. I have a pair of these in mono configuration and they are outstanding with the Sound Lab A1s. But I gotta believe a single VK600SE would be plenty. The result is not at all like I heard with the JC1's. Why the obsession with the JC1's in these forums is beyond me! Oh, and I did hear the RM200 amp several times at a dealer and every time, his system sounded wonderful. So this too may be an option, but it might run out of steam when you require a louder volume setting or are in a big room. Again, call VTL, Manley and ML to get the advice on these exact products and not be focused on white papers of other products. |
jafox, I have listened to JC-1 extensively. You can not find one even a little iffy review. They are all dramatically positive. My review is exactly the same. The only amp I have heard on ESLs sound better is the Pass XA 200.8 and I suspect the Atma-Sphere MA-2 is up there also. My assessment is that your review samples were hooked up incorrectly. It would be the only way you would hear something as bad as you relate.
I also understand that SoundLabs was using JC-1s in it's sound room. Transformers have all kinds of problems associated with their use. I am not educated enough to fully understand the issues but you can google this and like me you will probably be dizzy after the first page. The one I understand for sure is saturation. When the transformer saturates you hit a brick wall. It is pretty much like an amplifier clipping. But in the end it is the sound you like that matters. In my system tube amps can sound lovely but they have all lacked the dynamic punch necessary to recreate some music. This is only on ESLs mind.
bdp24, you know darn well that Jim Strickland was the first designer to put that stunt. I happen to know somebody who uses Jim's high voltage amps on his own ESLs:) I would love to see how Roger tackles this design. |
@mijostyn, I’m not sure of the year Strickland and Beveridge each introduced their direct-drive ESL (the first Beveridge ESL, the Model 1, was invented in 1965), but I do know Strickland discontinued his amp and went with a transformer because of reliability problems in the amp. Modjeski says he has repaired a few of them, and found it’s design weaknesses, designing a mod to correct them. One of his services is to rebuild the Acoustat amp, for which owners send him their broken ones. Roger was hired by Beveridge to solve the reliability problem in his direct-drive amp. Roger worked in an electronic repair shop in high school, and learned how NOT to build an amp. If a circuit calls for a 2w resistor, he uses a 20w. Trouble-free operation is a very high priority for him, in contrast to some more widely-owned high end brands who put other priorities first. When I bought my first ARC electronics, turning on the SP-3 pre-amp for the first time blew a resistor. I couldn't believe it. My dealer (Walter Davies, who co-developed his patented Last Record Care Preservative---which is NOT Freon ;-) put it on his workbench and had it up and running in a coupla minutes). That was a long time ago, and Bill Johnson did eventually learn the lesson he should have known long before (he too started his career as a repair technician). At a seminar I attended in the 1990's, Johnson talked about how a batch of bad parts almost put ARC out of business in the 1980’s. |
pvmike,
One assumes having posted the specs for the Manley 500 monos, these are the amps under consideration. I've not heard them, but am a long time owner of the Mahi Mahi and can attest to them being scary fast and able to handle many different speakers with ease within their power limits, about 40wpc, 25wpc triode depending on the speakers.
Manley tends to over build and invests heavily in power regulation. I would tend to believe these monos would handily power anything thrown at them. I took a pair of VTL Tiny Triodes to a shop once and powered their smaller ML speakers and they were shocked at how easily they drove them, how smooth they sounded and how quick it made the MLs.
I would not back away from the Manley amps.
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The Acoustat Model X was released with the direct drive amp in 1976. He came out with the Transformers somewhere around 1979 because the dealers were telling him that people wanted to use their own amps plus without subwoofers the direct drive amp would at best push things to 85 dB on Monitor 4s. I though the amps sounded beautiful but also wanted more dB which is why I jumped into subs way back then. The RH Labs sub was perfect for the Monitor Fours. You just took them off those silly plastic stands and plopped them right down on top of the woofers. Perfect fit. A set of Kenwood LO7-M mono amps and 95 dB was your playground. I never had any trouble with the direct drive amps. They were discontinued because nobody wanted them. I sold my system when I moved from Florida to Ohio. Jim Strickland had already set me up with a dealer in Akron who would deliver my first set of 2+2s at dealer cost + 5%. John Ashe of Golden Gramophone and I would become good friends. I got my Krell KMA 100s at the same time. Now 30-40 years later I am sure whatever direct drive amps remain are in need of help. Those oil filled Caps are probably leaking all over the place.
Roger is an interesting character. One thing I can say for sure is he knows how to find quiet 6922s. Last? Who said anything about Last? |
My assessment is that your review samples were hooked up incorrectly. No. The JC1's were not review samples. This was at a dealer for Atmasphere and Parasound products. The rest of his system was top notch. The only way to incorrectly connect an amp to speakers would be to reverse the speaker cable polarity; the result is immediately obvious with all instruments conveyed at the outer edges of the speakers rather than within the speakers. It would be the only way you would hear something as bad as you relate. Compared to the Atmasphere and CAT amps at that moment, the JC1's were severely dimensionally flat. That was just how it was. The dealer downplayed the result but to me, it was not subtle at all. Going back and forth between the two tube amps was an incredible experience. Nobody had any desire to return to the JC1's whose performance was in the mid-fi zone. I recently purchased a Symphonic Line RG1, a model near the bottom of the SL product line, and this amp is phenomenal with the A1's. This mid-sized, mid-powered amp portrays space and harmonic structure in a most impressive manner. Directly comparing the baby SL with the mighty CATs shows me how well engineered the SL amp is. As for Sound Lab dealers or show demos using JC1's as part of their setup is not surprising. I heard SL's at a So Cal audio show some years back and the system result was mediocre at best. I could not believe the midfi gear in that setup. One of those head-shaking moments. I wanted to go home and bring my tube preamp for his demo as it would have transformed the result. |
