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

(with the addition of a 3/4 ohm series resistor in the primary) which means they will drive anything.

You have successfully just made the damping factor that was already diminished because of bridging, even worse by installing even more series resistance, good work.

I was thinking that the extra power would improve almost everything about this, particularly in more dynamic recordings.

If you don’t use all the dynamic headroom power with a single stereo amp, you will gain nothing by bridging having even more. Headroom is head room, if you haven’t reached it there’s no reason to make it higher by bridging and taking a hit on everything else.

You just take that was a good stereo amp, send it down the path of becoming a mono P.A. amp because of the reduction in all the other parameters it will take a hit on by bridging.

You guys need to see the forest for the trees, if you want/need more power and want to have two of these stereo amps, just vertically bi-amp them, then you gain the power in the bass and dynamic headroom, without taking a hit on everything else if you bridge them.
http://www.av2day.com/wp-content/uploads/2014/05/biamp2.jpg

Cheers George

talk to Benchmark, then borrow one and find out which you prefer...real listening in your own system, not theoretically why you should or shouldn't...

though they are temporarily sold out...

@wwoodrum - only you can say whether you need more headroom with your room/speakers.
My room size is similar to yours and my speaker sensitivity around the same - and truthfully a single AHB2 drove my ATC’s to high levels without issue. Nonetheless adding a second amp improved the sound in terms of dynamic ease and soundstaging.
My motivation was not only the extra headroom but, as previously mentioned, the placement flexibility that mono blocks offered - allowing me to tidy up my setup using short speaker cables.

As you probably realise from the specifications, unlike conventional amplifiers, there is no downside to bridging the AHB2. The error correction circuitry ensures the Benchmark’s distortion remains vanishingly low as impedance drops/varies. This may well be another reason for the AHB2’s perceived neutrality vs other amplifiers - i.e. distortion in other amplifiers typically varies with impedance (whether bridged or not).
Of course the output impedance does double when bridged which means damping factor halves - in the AHB2’s case dropping from from 350 to 175 (at 20Hz/8ohms). This is still 10x higher than a typical transformer coupled tube amp and is unlikely be of much/any audible consequence. Certainly I heard none in my setup.

If you get a second amp you have the option to try both bridged mono and vertical bi-amping - so why not? For bi-amping you will need an XLR splitter of some sort if your preamp doesn’t have dual sets of XLR outputs.
Both options have the advantage of dedicating a single amp per channel and using short speaker cables. The bi-amp option further allows a seperate amp for woofer/tweeter - though most of the work is still being done by the amp on the woofer, which still has only 100W/8ohms.
You will gain a slight increase in headroom with the vertical bi-amp option while bridged mono will give a significant 6dB more headroom.
With more sensitive speakers, where extra headroom is redundant, the bi-amp option may well be preferable.
I use bridged mono and bi-wire to my ATC speakers (allowing removal of the link at the speakers).

I’m not going to gush over the improvements offered by the second amp as in overall terms they are not massive. Nonetheless, in my setup it does sound better.
Only you can decide if it’s value for money.
Some people spend more on speaker cables than the cost of an AHB2 amp so, if you’re into expensive cables, you could potentially save money moving to mono blocks and short cable lengths ;-)