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Review and Measurements of Benchmark AHB2 Amp

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It's $3000 now, which I find to be a little excessive.
Value wise, the B60 is pushing boundaries. Very good quality but at a price that's too high by about $600-800 if you ask me. I think Simaudio/Moons are better value, especially in the $2000-3000 range.
The Moon 240i (DAC integrated) was also in my upgrade shortlist, as well as the Hegel H190, also a DAC integrated. But then the AHB2 "came along". I can pair the Benchmark with a Topping D70 for about the same coin as the Moon and Hegel.

I've only discovered the Bryston B60 in this thread but the $ per watt is arguably encroaching high end territory.
 

GrimSurfer

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The Moon 240i (DAC integrated) was also in my upgrade shortlist, as well as the Hegel H190, also a DAC integrated. But then the AHB2 "came along". I can pair the Benchmark with a Topping D70 for about the same coin as the Moon and Hegel.

I've only discovered the Bryston B60 in this thread but the $ per watt is arguably encroaching high end territory.
So would you be running the Benchmark without a pre-amp?

My value choice in the Simaudio line would be the Moon 250i. Basically the same as the 240i, less the DAC.
 
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So would you be running the Benchmark without a pre-amp?
Yes. The D70 has a volume control plus an extra pair of outputs for a subwoofer. All my sources are all digital.

My value choice in the Simaudio line would be the Moon 250i. Basically the same as the 240i, less the DAC.
My concern with the Moon 250i/240i is the low power at only 50w. Plus their branding/marketing seems to have a subjectivist vibe. :p

The Hegel H190 however, made me really curious. The specs (below) look good, plus they talk about their SoundEngine technology which supposedly cancels crossover distortion and uses feed forward technology. I'm not an electronics engineer but aren't these the same tech in the AHB2 described by John?

Power output 2 x 150W in 8 Ohms, 2 x 250W in 4 Ohms
Minimum load 2 ohms
Frequency response 5Hz-100kHz
Signal-to-noise ratio More than 100dB
Crosstalk Less than -100dB
Distortion Less than 0.01% @ 25W 8 Ohms 1kHz
Intermodulation Less than 0.01% (19kHz + 20kHz)
Damping factor More than 4000

By the way, I'd like to ask a favor from the AHB2 owners: would you mind posting the box (carton) dimensions?
 

Xulonn

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FWIW, I own a 2B which resides in a closet because the mechanical hum from the power transformer is so obnoxious.
I once owned a McIntosh Mac1900 receiver that had a bad mechanical hum, and had only 4 bolts holding the power transformer core laminations together. Although McIntosh engineer Dave O'Brien denied that there was a problem when I took it to a clinic at a California Mac dealer, I noticed that later versions had 6 bolts holding the laminations together. Even McIntosh has cut corners at times.
 

GrimSurfer

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Yes. The D70 has a volume control plus an extra pair of outputs for a subwoofer. All my sources are all digital...

My concern with the Moon 250i/240i is the low power at only 50w. Plus their branding/marketing seems to have a subjectivist vibe. :p
Understood. All my sources are digital too.

I'm not concerned about the wattage. Am currently running a 30W high current (30A) amp with a high slew rate. It does just fine driving my 87 dB/W B&Ws to my typical listening levels.

WRT the subjectivist vibe, that's an intrinsic part of the industry... practically every manufacturer spews this kind of tripe.
 
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DDF

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My ~ 30 year old 2BLP (same amp as in B60):
- had to replace main PSU caps at 20 yrs. Bryston was great and sent freebies that I swapped in
- developed transformer hum as well. I made this inaudible (sits below my desk in my office) by tightening the xfrmr mounting bolts and by removing the lid (not safe if you have pets or kids). The steel lid creates a closed magnetic path that made the transformer hum too audible

I'm still enjoying this amp a great deal: purely seat of the pants subjective, it sounds dynamic and zero fatigue if a touch bright (but clean). It's no where near the detail, resolution or power of my Ncores that I put together for less, but they took a bit of work
 
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The Moon 240i (DAC integrated) was also in my upgrade shortlist, as well as the Hegel H190, also a DAC integrated. But then the AHB2 "came along". I can pair the Benchmark with a Topping D70 for about the same coin as the Moon and Hegel.

I've only discovered the Bryston B60 in this thread but the $ per watt is arguably encroaching high end territory.
Speakers are not a passive load. They generate its own voltage which then feeds back the amplifier. Amplifier then tries to damp these parasite signals the best way it can - but it's never perfect and various amplifiers do this with various success. Measurements being done with passive resistance don't cover what will happen with real speakers. Does it generate additional distortion, this feedback from speakers? Why, of course it does - there's a parasite signal that should not be there at all in an ideal case - which never happens in reality.

Also, music is by its nature is full of transients, short bursts of peak current being drawn from the amplifier, while relation of transients power to RMS is said to be 10 to 20 times. Meaning, if you listen at the average power of 15W, peak power may get as high as 300W. While some amplifier may have, say, 100W RMS (all numbers per channel) - and still it will be asked to deliver those 300W peak power - and a as a listener, you want the amplifier to deliver those transient without clipping them, with as little distortion as possible (of all kind, both harmonic and intermodulation distortion). If the amplifier was only measured up to its RMS (or lower), you still don't have the info what happens with those peak music signals with power above declared RMS (unless it's already pretty bad below declared RMS).

On top of this all, speakers impedance will vary which further increases demand for peak power...while at the same time it may have its capacitive/inductive part of the load (phase), which make things yet more demanding to the amplifier.

And this is not nearly all.

All in all, one who looks in whole complexity of amplifiers, understands that set of measurements performed simply cannot seriously cover all what it takes to make a correct, objective evaluation of the amplifier. The only proper way to assess the amplifier is to actually connect it to the speakers you want to pair it with...and listen to it. Best when using a variety of music content and enough time span to evaluate it properly. The traditional way, still unbeaten. But whoever trusts those few graphs to tell him all he has to know about the amplifier...well, good luck to you, folks :) you're gonna need it...
 
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if you listen at the average power of 15W, peak power may get as high as 300W.
It seems more likely that in most residential rooms with speakers of typical sensitivity and efficiency, average amplifier output power is probably more like 2 watts or less. I think your estimates are high, unless we're discussing sealed subwoofers in large rooms used for actions movies with audio special effects.
 
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It seems more likely that in most residential rooms with speakers of typical sensitivity and efficiency, average amplifier output power is probably more like 2 watts or less. I think your estimates are high, unless we're discussing sealed subwoofers in large rooms used for actions movies with audio special effects.
Well, at average 15W those transients (peaks) will likely be clipping if the amplifier is not quite a powerhouse, so no wonder we actually don't listen at those levels. No such issues when average power is couple of Watts or less.
 
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Assuming the VU meters on my Sony amp were correctly calibrated, I usually listened between 0.001W - 0.1W. When it was really loud 1W. Never saw more than 10W on the meters. Then again, VU meters are integrating over time by the inertia of the indicators, so any short peaks will not visible.
 

amirm

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Do amplifier test measure dynamic performance or infer it using steady state resistive loads?
Does distortion always remain low at all frequencies when driving difficult reactive loads?
Are amplifiers always linear or do they have momentary sags?
Perhaps, amplifier measurements are complete, but I'm not so sure.
We could do more with respect to measurements. Question is whether we confuse the readers and overwhelm them with information. For example, some reviewers use square wave and show those waveforms. The ones that don't know what they are doing use fast rise-time square wave which cannot happen in our audio-band music.

With respect to difficult loads, we could add reactive ones. I tried to build one but faced resistance on them being too difficult than typical speaker loads. At the end of the day, they just lower the impedance of the load at higher frequencies.

Note that sine waves are more difficult load for the amp than music. They have every low crest factor, pushing the amp to deliver more power than music would. So our simplistic test here is actually more extreme than the real application. The capacitors in the power supply for example work a lot more effectively with ups and downs of music than sine wave we use for measurements.
 
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Nothing like the power of the internet to move products in an extremely niche market.

I hope benchmark send you a gift basket Amir
 
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The capacitors in the power supply for example work a lot more effectively with ups and downs of music than sine wave we use for measurements.
That's for sure, since most amplifiers cruise along at a watt or two of output per channel most of the time with music. Sometimes I wonder how amplifiers would be designed if sine wave testing was not a factor at all. On second thought, I think I know the answer; many might come out looking like Nelson Pass's First Watt amps. I'm only kidding. Or am I? ;)
 
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Congrats! Can you please post the carton dimensions?
Sure. The Benchmark box is 39x33x18. cm that is. I'll leave it to the americans to convert it to freedom units :D It was delivered to me in a larger box that measures 50x40x30.

e: Here's what it looks like opened:



It's surprising how heavy this little thing is, then again it weights nothing against other 'serious' amplifiers.
 
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Thanks. We at ASR should leave no measurement unmeasured.

In all seriousness, there is no Benchmark dealer in my country, so I'm thinking of creative ways to bring one home.

Thanks for the bonus unboxing too.
 

Sal1950

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DUE TO HIGH DEMAND WE ARE CURRENTLY OUT OF STOCK.

Fake news to justify a price increase for the next batch. :eek:

Just teasing John. ;)
 
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