Benchmark ABH2 compared to Merrill Element Series and other ultra high end amps

I haven't made the comparison, but I'll soon be comparing the Benchmark LA4 preamplifier with the Boulder 1012...

@dr_joe I hope you can post some info on the comparison. I am interested in the LA4 vs something in the Boulder 1012 price range, the Mola Mola Makua. 

Just keep in mind the ABH2 only offers up 100w into 8ohms and 200w into 4ohms and 380W into 4ohms if running bridged mono. You’re very much likely to trip the amps protection circuits if you’re driving it into sub 4ohm loads since when running in bridges mode the amp is seeing half that.

Peronally I wish benchmark offered a more powerful version but Perhaps if they did that they couldn’t stick to the “Benchmark” philosophy of having the best stats on the market. There are trade offs with any design of any piece of electronic equipment.

The aforementioned uber amps, by constellation, pass labs, Solution tend to offer much more wattage and stability into 1ohm loads. Not even sure if the abh2 is stable into 1ohm, let alone 2ohm in stereo mode.

At different times, I heard a single AHB2 and stereo Merrill Element 114 at home.  The AHB2 was more neutral at continuous low/moderate SPL's, but it shut down at moderate SPL peaks when driving my inefficient electrostatic speakers.  The 114 was warmer/sweeter, more dynamic, with fuller bass.  Bridged AHB2's are probably more dynamic than a single AHB2, but they shouldn't be used if the inefficient speaker has very low impedance at certain freq.

Thank you viper 6.  I have Martin Logan CLX's and have heard mixed reviews of the AHB2 with full range stats.  Most comments seem to find that bridged mono'ed amps work better than a single amp into full range stats.  Benchmark maintains that bridged mono'ed amps are stable into low impedances.  I appreciate your comments regarding the Merrill 114's.  I am curious as which electrostatic speakers you are using.

soundhound OP
Most comments seem to find that bridged mono’ed amps work better than a single amp into full range stats

Most comments are BS then, as the ML’s ESL's present down to 1ohm loading and this is not nice for bridged amps, let alone good non bridged.

Benchmark maintains that bridged mono’ed amps are stable into low impedances.

So is a 1980’s $299 Nad 3020 receiver stable into 2ohms, doesn’t mean it will sound good

Cheers George

soundhound,
My electrostatics are the Audiostatic 240 from early 1980’s. They are still the most detailed stats I have ever heard, although I admire the ML CLX as next best. My 240’s are mellowing out compared to when I got them nearly 40 years ago, so I have added the Enigmacoustics Sopranino electrostatic tweeter in parallel. This gives me SOTA HF, but the impedance combo at the highest output 8kHz setting is probably 1.5 ohms or so, with a weird phase angle, so most amps are severely limited in the power they can deliver without shutting down. I make this sacrifice in power for the glorious brilliance at lower SPL’s which is doable for most classical music I listen to.

Not sure the Benchmark would be a good match if you want to look at a more modest priced alternative to the Merrills look at the Anthem M1 monoblocks.  

I am sure that the Audiostatics are great speakers and like most full range or nearly full range electrostatics they present the driving amp with a capacitive load with high to very high impedances in the bass and low to very low impedance in the mid to high treble region.  The obvious exception are the Quad 2800 and 2900 series.  John Atkinson measured a minimum impedance of 3.3 ohms at 10 kHz and then rising with an inductive load for the 2912's.  The only impedance curve that I have seen for the CLX's was published by hifi world; the impedance for the midrange/treble panel on the Montis published by Stereophile is probably representative of what a more detailed curve would look like to the CLX midrange/treble panel.  The impedance in the bass is capacitive and over 30 ohms for the CLX at 50 Hz at the lower end of its range and falls to 4 to 6 ohms in the upper midrange and lower treble.  It falls to 3 ohms at 6-7 kHz and then down to 0.7 ohms at 18-20 kHz all capacitive.
I suspect that the impedance in the bass is unusual due to compound bass driver in the CLX.  Also the sensitivity of the CLX as estimated by British hifi mags was closer to 85 dB than the 90 dB published by Martin Logan.  This long discussion likely has much to do with the difficulty many amps have in optimally driving the CLX.

Since starting this thread, I tried out a single Benchmark amp.  It was as advertised extremely transparent and able to resolve small details.  However, it lack lower midrange to bass dynamics compared to many other amps I have had, Pass Labs 100.5's, Krell 402e, and Coda No. 40 and 15.5.  It also seemed to have a lack of tonal color and density.  I have spoken to knowledgable personnel at Martin Logan.  They have used the Benchmark in mono'ed mode with their hybrid speakers which do have a low treble impedance without any problem; however, they did not comment on the compatibility with the CLX.  Other reviewers, particularly Doug Schroeder, found the mono'ed amps to be noticeably better than a single amp.  Other CLX owners have noted sonic improvement with mono'ed amps.  Benchmark has told me that mono'ed AHB2's can handle the low treble impedance of Martin Logan speakers.  A priori, I would not have guessed such a synergy but I have no reason to doubt the observations of several experienced reviewers and audiophiles.  

I remain curious to try two mono'ed AHB2's with the CLX's but am also curious as to whether I would be better served by one of the newer Merrill amps.  

I did own an AHB2 and yes, it’s very quiet, distortion free. I was happy and then a friend brought over his 30 year old Mirror Image Audio amp a to try out. This amp made the AHB2 sound thin and lifeless in comparison. I now have a Coda #8 and It is even better. The AHB2 just doesn’t have enough meat on the bones for me.

I am now using a recently manufactured Coda 15.5 which has the newer low noise input devices.  My perception of a single AHB2 on the CLX are as above  and consistent with lancelock's observations.   The Coda 15.5 is an excellent class A amp and is able to drive the CLX's well with tonal density, dynamics, bass response and excellent detail provided the upstream components including cables can provide such.  My overall impression is that the Coda is more satisfying than a single AHB2, but that the AHB2 may have a small edge in very low level detail retrieval.  In audio, we would like to have it all.

I should add that this small edge was only seen when using an LA4 preamp with the AHB2 input in the lowest gain setting.

@soundhound

I failed to mention that I’ve had the Coda #8 for about 2 weeks and I’m sending it back.  I will be exchanging it for it’s big brother the Coda #16.  I loved the #8 so much that I’m now going straight to the flagship amp as my end game.

I am sure that you will really enjoy the No. 16.  The differences between  the most 15.5's and the new 16 are the inclusion of newer low noise input transistors and an increase in the capacitance in the power supply from 200,000 microfarads in the 15.5 to 280,000 in the 16. I am fortunate to have a 15.5 which has the same lower noise input transistors used in the 16 but I am sure that the augmentation of the power supply will translate to improved performance.  Congratulations.

@soundhound Did you ever try the LA4 and AHB2 with the XLR cables that Benchmark recommends? Such as the low cost Benchmark Star Quad XLR's?

This is info I gathered from the Benchmark website regarding the XLR's to use..

Professional grade XLR, that support 24 dBu signal level and have CMRR specifications on balanced inputs?

I have much more expensive Audience XLR's compared to the Star Quad on my new DAC3B and HPA4 peamp and while it sounds great I want to hear the configuration Benchmark is suggesting is the best combo for their gear. I think Benchmark considers my Audience XLR's consumer grade gear.

BTW - I bought the HPA4 a few days ago and your comments  on how the LA4 sounded with the CODA 15.5 helped me get that instead of the 2 more expensive alternatives I was favoring. I love the HPA4. I am listening to headphones now late at night and it is great musical experience with the HPA4. Slowly starting to buy the gear I mentioned.

I have not tried the Benchmark XLR interconnects as I received advice from other users that they were decent but were bettered by a number of high quality interconnects. Benchmark amps and preamps do benefit from audiophile grade cables - including power cords, interconnects and speaker cables - although their literature does not acknowledge this observation.

The AHB2 is a special amp given the right load. It is not a good amp for ESLs. As soundhound mentioned ESL's drop their impedance as the frequency increases. Even mono strapped AHB2's  do not do well. However with an 8 ohm or higher, efficient speaker say like a Klipsch the little amps kick ass. They are priced lower because Benchmark makes professional equipment and the market is priced differently. They also really have their act together. I have their ADC and it is a little jewel. Beautifully constructed. I have no trouble recommending their equipment under the right circumstances. Don't let the price fool you. Benchmark stuff is as well made as anything out there. 
I have never been close to a Merrill amp. 
As far as ESLs go, and I have been using them for decades the JC 1 is very hard to beat. They make my stats thunder. Pass amps do very well.
The best may be Atma Sphere MA 2s.
 I am not an ML fan. Curving a panel is a silly idea and the man who designed them, Roger Sanders agrees. As far as Hybrid ESLs go Roger makes the best and they are very easy to live with. His amps also do a fine job driving ESLs. Sound Labs currently makes the best ESLs available by a fair margin. But, they are no compromise speakers and even the small ones will dominate a room. The big ones own the room. They are huge but boy are they special. They were using JC 1's to demo their speakers.     

@soundhound Thanks for the feedback. It is what D Schieder (sp?) said in his Dagago review but that was only 1 person's feedback. I am also using good interconnects, Audience Au24SE (not sure of exact model). It sounds great. I contacted Audience to ask if these XLR's can carry a 24 dBu signal and the person responding to me did not know, though I imagine someone there would know.

I can add to the AHB2 with demanding speaker. I demoed a single stereo AHB2 with Magico A3 and compared it to the 2 Mark Levinson amps that were under consideration.  The 585 integrated and the $20K mono blocks. The AHB2 was the worst performer. However, at home on my KEF LS50's the AHB2 sounded much better. I attributed this bad showing to not enough power in stereo for the A3.

I sold the ABH2 after that demo. However, now that I have the HPA4 preamp I will be getting the AHB2 again to pair with the LS50 speaker. On that speaker the AHB2 sounds excellent.

soundhound,
You cannot have it all in any system.  If you like fine stats like the ML CLX, you value accuracy and detail.  The Benchmark AHB2 is an accurate amp in like manner.  There are certainly many amps that emphasize power and large scale dynamics, which will make the stat sound more like a dynamic speaker.  Unlike people who say the AHB2 is lifeless, I find that other amps which are fuller and rolled off in HF by comparison, take away from the exciting subtle musical detail that the AHB2 reveals.  The Merrill 114 is worth auditioning if you want warmth and fullness in lower midrange and bass.

I can see from the comments that there are many opinions most of which are well grounded. I regularly attend live concerts - principally symphonic and opera.  I was fortunate to attend two performances of the Metropolitan Opera in February before the pandemic hit New York.  When listening to recorded music I value natural timbres, the minimization of distortion, and the ability to follow the musical intent of the performers.   I agree that the AHB2 has a low noise floor and so reveals details that help to convey the intent of musical performers; in my system I was disappointed that a single amp did not provide accurate timbres from recordings of artists  that I have heard live. No system that I can afford will provide a perfect replication of all live music.  However, one wants to optimize their system within the limits of their resources. Experienced listeners reviewers, not a single individual, have had good results with AHB2's driving electrostatics, including a single AHB2 driving Quads and, contrary to my naive expectations, good results from mono'ed AHB2's with other electrostatics including the CLX and hybrid ML's.  When I started this thread some months ago, I did not have any first hand experience with the AHB2.  I probably need to audition the mono'ed AHB2's, the newer Merrill amps and probably the Constellation Taurus as well.

soundhound, 
Yes, I agree.  As a violinist, I enjoy the sound under my ear and a few feet away playing string quartets, and playing in the orchestra.  Unfortunately, as a concertgoer sitting even in the 1st row center, my perceptions have been greatly diluted in the amount of musically important detail I have heard, compared to my close encounters as a player.  The first row is approximately the sound "heard" by the microphones in most recordings, so to make a valid comparison between your system and being there, the 1st row is the approximate reference.  Even the 2nd row is veiled compared to the 1st row, because high freq are short wavelengths which are absorbed by any distance.  One day, when playing in the 2nd violin section, I sat close to the French horn.  Usually on recordings played on most systems, the horn is an amorphous glob of vague sound, but sitting close I heard lots of rawness and spiky attacks in the tone even when the music was sostenuto.  Most people think of the horn as a smooth midrange instrument, but James Boyk showed that it has significant overtones as high as 9kHz.  The tuba has lots of bass energy, but it also has significant high freq overtones that enhance its clarity and power.  On most systems, the tuba sounds like wooly muddy thuds because HF are not sufficiently revealed.  

So to reveal the truth, I want an amp to have as much detail as possible.  Since we cannot have everything in any system, I have made the choice to go for components that sacrifice bass extension and fullness in order to get maximum detail in mid bass and higher freq.  The ML CLX is a great example of such a speaker that rolls off bass at 56 Hz, which has the effect of maximizing the clarity where most of the music is.  Although I have never heard the flagship Neolith, my guess is that it does not have the clarity of the CLX in that range, although it appeals to the bass lovers.