Review and Measurements of Benchmark AHB2 Amp

[misterdog]

Seems like a well thought out configuration.

Even including slotted mounting holes for the fixing bolts, allowing for extra ventilation from the front....

 

[JP]

Even including slotted mounting holes for the fixing bolts, allowing for extra ventilation from the front....

?

 

[Descartes]

I know amir hates this dude, but this pretty much summed up my experience:

I'm certain the AHB2 is a great amp, but it just wasn't for me.

What was the issue!

 

[misterdog]

Too accurate and neutral for him, he prefers valves.

 

[yzbythesea]

I really wanted to like this amplifier. I ordered this and used my RME ADI-2 DAC straight into it to drive my KEF Reference 3's. The sound was cold, clinical and sibilant. I was hoping I could replace my Naim Uniti Nova, the big brother to the Atom, which was recently reviewed and trashed by Amir. End game amp for $3k? Hell yeah, I thought. Guess I'm one of those "euphonic distortion" guys.

I had the same feeling about this amp. I listened to this amp at my local dealer shop (paired with benchmark dac3 and preamp) with my own speakers (elac vela). It is a very accurate amp with a lot of details, but yes, it sounds cold and boring to me. I guess my music taste prefers more dramastic rendering and "musciality", which distortion sometimes can help

 

[restorer-john]

A rack mount installation brings with it the possibility of reduced ventilation or air circulation above (and below) the unit. So heat sinks are a completely reasonable feature in that configuration. Also note that the silver edges on the sides of each version are different thicknesses: it appears the heat sinks are not merely stuck on to the standard model’s exterior, but instead the rack mount model seems to have different side panels with the integrated heat sinks that run through to the inside walls of the enclosure. Seems like a well thought out configuration.

For sure, but if a rackmount 19" panel is enough to cause the unit to overheat and require the AHB-2s heatsinks, then it was marginal in the first place. I don't believe that, but cosmetic heatsinks are a thing these days- just ask Rotel, they did it for a decade or more and there's plenty of amplifiers using heatsink extrusions as casework with no devices attached.

Maybe the grain finished and polished anodised side panels are actually more expensive for Benchmark than the AHB-2 anodised heatsinks- did you consider that? And nobody is going to care if they mount it in a rack...

The image I posted appears to be a rendering anyway- look at that volume knob- it aint right.

 

[tmtomh]

For sure, but if a rackmount 19" panel is enough to cause the unit to overheat and require the AHB-2s heatsinks, then it was marginal in the first place. I don't believe that, but cosmetic heatsinks are a thing these days- just ask Rotel, they did it for a decade or more and there's plenty of amplifiers using heatsink extrusions as casework with no devices attached.

Maybe the grain finished and polished anodised side panels are actually more expensive for Benchmark than the AHB-2 anodised heatsinks- did you consider that? And nobody is going to care if they mount it in a rack...

The image I posted appears to be a rendering anyway- look at that volume knob- it aint right.

I don't know where you're getting the idea that it's about the addition of the panel - that's not what I wrote, which is clear as day in my prior comment: a rackmount installation brings the possibility of no/minimal ventilation ABOVE AND BELOW the unit, as when someone has a stack of units in a rack with no gaps/blank panel spaces above or below. In addition to misreading my comment, you're also making a suspect assumption that Benchmark adds heat sinks to the sides of the rackmount version because if they didn't, the unit would overheat. A more plausible assumption IMHO is that Benchmark has a certain thermal target, and then they build in a fair amount of safety buffer to that beyond, so their units can be reasonable assured of running cool and lasting a long time in a variety of use environments, and so they also minimize customer service contacts for hot-running units. If a free-standing, non-rackmount unit is designed to a certain thermal target, then the possibility of less passive ventilation in a rackmount application could quite reasonably lead them to add heatsinks to raise the likelihood that the rackmount application will result in a similar thermal situation.

What this boils down to is what it always boils down to when you decide that a manufacturer or a piece of equipment is about marketing BS and bad engineering - you interpret everything you see and read about that manufacturer or unit in whatever way you have to, no matter how implausible or selective, to reinforce your initial conviction.

As for how the volume knob looks in the image, that's just silly - the jpg lacks the resolution to know if it's a photo or render, and whether it's a photo or a render is irrelevant and tells us nothing with regard to the argument you're trying to make. You're just saying it looks like a render to try to cast doubt on Benchmark's truthfulness - throwing everything at the wall to see what you can make stick. Not very scientific.

 

[MaxBuck]

... it sounds cold and boring to me. I guess my music taste prefers more dramastic rendering and "musciality", which distortion sometimes can help

Dramastic rendering and musiciality are always preferable.

 

[xaxxon]

Dramastic rendering and musiciality are always preferable.

I find incredible levels of precision and accuracy to be quite dramatic.

A bad amp will make every recording mediocre. A good amp allows good recordings to sound good. I'll just listen to the good stuff.

 

[Gaussgodden]

Can two of these benchmark ahb2 drive b&w 801 matrix series 2 well enough. With good bass output. I understand the amp is crystal clear, but pairing the b&w with some light weight high watts amps sometimes can't get the bass going.. thanks

 

[restorer-john]

I don't know where you're getting the idea that it's about the addition of the panel - that's not what I wrote, which is clear as day in my prior comment: a rackmount installation brings the possibility of no/minimal ventilation ABOVE AND BELOW the unit, as when someone has a stack of units in a rack with no gaps/blank panel spaces above or below. In addition to misreading my comment, you're also making a suspect assumption that Benchmark adds heat sinks to the sides of the rackmount version because if they didn't, the unit would overheat. A more plausible assumption IMHO is that Benchmark has a certain thermal target, and then they build in a fair amount of safety buffer to that beyond, so their units can be reasonable assured of running cool and lasting a long time in a variety of use environments, and so they also minimize customer service contacts for hot-running units. If a free-standing, non-rackmount unit is designed to a certain thermal target, then the possibility of less passive ventilation in a rackmount application could quite reasonably lead them to add heatsinks to raise the likelihood that the rackmount application will result in a similar thermal situation.

What this boils down to is what it always boils down to when you decide that a manufacturer or a piece of equipment is about marketing BS and bad engineering - you interpret everything you see and read about that manufacturer or unit in whatever way you have to, no matter how implausible or selective, to reinforce your initial conviction.

As for how the volume knob looks in the image, that's just silly - the jpg lacks the resolution to know if it's a photo or render, and whether it's a photo or a render is irrelevant and tells us nothing with regard to the argument you're trying to make. You're just saying it looks like a render to try to cast doubt on Benchmark's truthfulness - throwing everything at the wall to see what you can make stick. Not very scientific.

You're funny, I was attempting to somewhat agree with you. But you can't help yourself.

But what I wrote, I stand by. The LA4 unit is a sealed box. If it actually genuinely needs heatsinks in a rackmount situation (which I don't believe it would), it is marginal for heat disipation in the first place. Can you honestly not agree with that?

Benchmark say: LA4 is identical to the HPA4 except that it eliminates the headphone outputs.

Here's the interior of an HPA4 (so the HP stage at the front will be missing/depopulated):

How exactly are a pair of heatsinks down each side going to benefit this layout? The entire unit pulls only 12W.

Anyway, Benchmark produce some great stuff, nobody denies that, but some of their claims and graphics/papers/methods to market their stuff leave a lot to be desired.

And, if the image was a render, they could have also mucked up the heatsinks- crazier things have happened.

 

[xaxxon]

Can two of these benchmark ahb2 drive b&w 801 matrix series 2 well enough. With good bass output. I understand the amp is crystal clear, but pairing the b&w with some light weight high watts amps sometimes can't get the bass going.. thanks

You're going to have almost 400 watts to play with -- yeah, it'll get the bass going.

I have monoblocks on my wilson alexias and they will shake the floor (though with a little bit more power available as they're 4-ohm)

 

[xaxxon]

some of their claims and graphics/papers/methods to market their stuff leave a lot to be desired.

Curious what you think is wrong/bad/whatever.

It sure seems more fundamentally sound to me than most marketing technobabble. But maybe that's just higher quality technobabble

 

[Ro808]

This Herb Reichert quote deserves some hot light:

«I use Chesky recording sessions to review headphones because I can compare what I hear live to the sound coming off the so-called “mike feed.” The Border Patrol DAC reproduced the church walls, the reverb, the positions on the floor where the musicians were standing, and all the subtle breathiness of Macy Gray’s voice. With the Benchmark, the majority of that information (which is definitely on the master file and appears via David’s $100K MSB DAC and via my Holo Spring DAC) disappeared !!! Your neutral DAC “stripped” away information that is unquestionably on the master file. Not to mention the BM DAC made it sound hard cold and harmonically threadbare. I call this subtractive distortion. Did you measure any of that?

My definition of accurate is: the DAC that makes a real piano in a real room sound the most like a real piano in a real room is the most accurate.

My definition of a neutral DAC is: the DAC that preserves the most information I know is on the file or tape.

What is yours?

Peace, love, and jangling keys,
herb».


Source: https://www.stereophile.com/content/nothing-what-i-want#JT6ykJu1xKKl42dy.99

You won't get many thumbs up, while - or precisely because, this quote touches on the essence of (digital) audio reproduction.

 

[thecheapseats]

I did an experiment the other day. I got fed up of all the audiophool networking aficianados telling me that I needed audiophile switches and cables because ethernet noise pollutes the DAC output. Yeah, whatever....

So I recorded a -120dBFs noise track in REW, converted it to flac and loaded it into Roon. With the DAC3 HGC in calibrated (0dBFS mode), I wound up the volume on the HPA4. At 0dB, there was nothing, zip, nada, SILENCE. At +4dB, I could hear a fain hiss from the tweeter (with my ear against it).

What was I hearing? Noise? A -120dBFS track? So I made another test track, this time with a -120dBFS 1 kHz 50% square wave.

Lo and behold, @ about +4 dB gain, I could hear........





wait for it........









the 1 kHz test tone!!!!!



Need to hook up my digital 'scope to the amp outputs and see what it looks like. Sure, there was some hiss with it, but the tone was unmistakeable. I'm honestly flabbergasted that a Benchmark DAC3 HGC, HPA4, and bridged AHB2s can pull an audibly recognisable 1 kHz tone out of a -120 dBFs test track.

Categorically proved that all this network noise/fibre isolation/LPS stuff is a load of hooey. Not only that, my endpoint is a humble RPi 4B with touch screen running Ropieee and powered over PoE by a PoE HAT which has a little SMPS on it.

Hats off to Benchmark Media for absolutely stunning performance!

great post @gfinlays... to further abstract the silliness ->> to survive, human hearing developed it's keen ability to hear predators - so as not to be eaten by local bears... therefore one must certainly give credit to the aforementioned 'aficionados' for their ability to defeat thousands of years of human hearing evolution and stealthily prey upon those who believe they can hear what isn't there...

 

[Heyu]

Will the Benchmark ahb2 be a better amp for my Magnepan LRS or is my current Parasound hca 1500a amp good enough?

 

[MaxBuck]

Will the Benchmark ahb2 be a better amp for my Magnepan LRS or is my current Parasound hca 1500a amp good enough?

You're unlikely to hear improvement with the Benchmark, though it definitely measures better. Not sure changing the power amp is where I'd be spending my money.

 

[Geert]

my endpoint is a humble RPi 4B with touch screen running Ropieee and powered over PoE by a PoE HAT which has a little SMPS on it.

That's terrible. A $5400 Sean Jacobs DC4 linear power supply would make your 1kHz square wave sound like nightingales whistling

 

[Heyu]

This amp shuts down the unit if stressed. Is this because of its low wattage and current specs at really loud levels it can't manage?

 

[DonH56]

This amp shuts down the unit if stressed. Is this because of its low wattage and current specs at really loud levels it can't manage?

Any amp should shut itself down if operated beyond its specs ("stressed"). What matters is if it can deliver the power you need for the volume you want. You could look at an online calculator to get an idea: http://myhometheater.homestead.com/splcalculator.html

The AHB2 has more sophisticated monitoring and protection features than most amps.