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......:))