Benchmark AHB2 - To 'mono' or not to 'mono'

You likely have the settings wrong/not optimized. Have you read up on the Owner's Manual to understand how to use the three position output switch in the back? I always tried all three positions with speakers, and there is a world of difference in performance/sound between the three positions. If you are using the wrong setting, then the amps will inhibited, weak on the bottom end, etc.  

I recall that if you are using XLR ICs there is one output position that is not recommended to be used. Perhaps this is the problem. If you haven't read the owner's manual, read it. Also, can you be sure that the internal output pads have not been adjusted? That is another aspect of the amp that you will want to read about. 

Also, most definitely work with the interconnects and power cords. Try at least three different power cords on the amps. 

Lastly, read up on the Schroeder Method of Interconnect Placement. Doubling the IC transforms the performance of the AHB2. It is a "do at your own risk" activity, but excellent results are being reported under the thread that bears my name in the Cable forum. 

No need to freak out; there are many settings and many permutations before you declare the amp is not good in Mono. If you work through all the permutations I'm sure you will find it to yield superb sound.  :) 

BTW, I advise you ignore break in and work actively to do changes that you will hear immediately.

I deleted my post earlier above, but it essentially mirrored douglas’ first paragraph.

Hi @douglas,
Thanks for your comments.
I had been using Benchmark DAC2/3 with single AHB2 for the past one year and couldn't be happier. I am very comfortable with the different input/output configuration and settings on DAC and AMP. The XLR jumpers are at factory setting of 0db, and ahb2 gain is at lowest setting (as per user manual). I never had to change the settings and now with 2 amps in bridge-mono mode, it is the same.(using same set of inter-connects and speaker cables what I was using earlier). I want to stay within manufacturer recommended settings and not do anything which will breach the warranty terms & conditions.

After being disappointed with mono-bridge SQ, I have now tried @georgehifi's suggestion of verticle bi-amping. I still do not have all the splitters/connectors/speaker cable to test that theory to its fullest, but put the amps in stereo mode and using one amp each speaker (bi-wiring at speaker end). I can already see, what @georgehifi was saying, and where I can go with this approach.

With this approach, the sound-stage is just mind blowing, which has +ve impact on overall enjoyment/experience. I am hearing things which I never heard on the familiar tracks and that too on the very low volumes. The overall SQ has improved. Its just more musical (to my ears). 

For me (and my ears) bridge-mono is definitely out. My next steps are to get to verticle-bi-amping setup.

I do want to thank all the experienced and knowledgable people on this forum. Its a great place to learn about this passion. I am amazed by the level of commitment of members on this forum to help other fellow members. A big thanks to you all! 

(May be one day I will try mono again......:)) 

ssnkssnk
After being disappointed with mono-bridge SQ, I have now tried @georgehifi’s suggestion of vertical bi-amping.
I can already see, what @georgehifi was saying, and where I can go with this approach.
With this approach, the sound-stage is just mind blowing, which has +ve impact on overall enjoyment/experience. I am hearing things which I never heard on the familiar tracks and that too on the very low volumes. The overall SQ has improved. Its just more musical (to my ears).
For me (and my ears) bridge-mono is definitely out.

Glad you found that out, as I’ve said many times all you gain from bridging (mono’ing) amps is extra wattage, but every other measured parameter that makes for a good amp take a hit for the negative.
Please let us know once you’ve got vertical bi-amping setup with better cabling that you want to get, how much further the sound quality progresses.

Cheers George

Seems a lot of people are bridging these.  I think I understand why people decide to do this.

The amp excels in micro-detail (or "micro-nuance" if you will).  But it also sounds somewhat constricted and anemic in my system, even with 89 dB efficient speakers which don't have terrible impedance swings.  When I use my class A tube amp or class D hypex they both sound more open and powerful.  In addition they both (especially the class D) have better defined bass than the AHB2 - despite the number of people who extol the AHB2 bass.

So I am guessing that if you want to experience the micro-detail and also want to have macro-control over the speakers, mono bridging may be the way to go.

For those of you who have a really good Class A or Class D amps, the AHB2 in stereo mode may sound a bit wimpy, and therefore may not necessarily provide a better listen experience, largely dependent on the type of music you listen to. YMMV.

YMMV indeed.

Most assuredly, the amp is not the only part of the equation.  I use 2-way Joseph Audio Pulsars and am not trying to power a large woofer, and with the AHB2, they give me every bit of bass that I expect and then some. Other people have commented similarly when they listen to my system. 

And just an update: Since my original post, I have been trying different brands of cables and have settled on some that I think have improved the overall sound and dynamics vs. what I had been using - none of which were cheap cables, by the way. I think my next investment is the Graphene upgrade to the Pulsars.

Thanks to everyone for their input.

I also have a single Benchmark AHB2, driving Fyne F-702 speakers from a Rogue Audio RP-1 preamp.  My previous amp was a Macintosh MC2120 that I bought new 42 years ago and had completely refurbed about 12-15 years ago.  When looking to replace the Mac, I looked at Parasound and the Rogue Audio’s Dragon and Stereo 100.  what prompted me to replace the 2120 was that the speakers did not sound quite as good in my home as in the dealers residential style setting.  My first though pt was more power, but the 702s are fairly efficient at 92 db.  After reading numerous reviews and noting that Benchmark has a 30-day audition period, I ordered the AHB2, receiving it four days later—with it having a production date of a few days before arrival.  After getting everything hooked up and listening for several hours, I have concluded that the audition period is not needed.  Even my wife, who likes music but is not “into” listening thought the difference was astounding.  Incredible clarity, silent background, excellent soundstage and reproduction of individual instruments and what I suspect is the harmonica of individual instruments.  Strings sound fuller, and I hear the full character of, for example, the different brass instruments—French Horn, trumpet, coronet, baritone, trombone.  Finally, bass reproduction is superb, even at lower volume levels.  The improvement was simply astounding.

Our room is not too large, which led me to consider the less powerful amplifier (100 wpc for the Benchmark vs 120 for the McIntosh MC2120).  However, I can achieve fairly realistic listening levels with my Rogue preamp at the 40/42 (of 60) on the preamp volume control, with no signs of clipping from the Benchmark.  Given the other comments about using the Benchmark in the mono mode, if I were to conclude I needed more power, I would use two in the stereo mode, with one amp driving each speaker vertically, voting for clarity over raw power—although 200 watts per channel is a good bit of power.

Mono is almost always better with the AHB2, except with my hard to drive Thiel CS3.7. The stereo amp is actually better suited than the mono since it can go down to 2 Ohm area. I now use the AHB2 with KEF LS50's but once I get a more AHB2 suitable speaker, I will re-buy the second AHB2 that I sold. 

The AHB2 becomes quieter, plays louder, and stronger in mono. I know from prior experience with other speakers.

I also do not buy expensive interconnects to hook up the AHB2 since it is AES48 compliant. I use 15-foot Benchmark XLR's. The AHB2 benefits from good speaker cable. I use Audience FrontRow with SpeakON termination at the amp end. You can also use short cables when you go monos and use the cheaper XLRs for the longer lengths to the AHB2s from the preamp,

The AHB2 is my favorite amp though I have others that cost much more.