Review and Measurements of Benchmark AHB2 Amp

[phoenixdogfan]

It is easy to fool oneself over these things, but I can attest, at least subjectively, to the gear's goodness. When my AHB2/DAC3HGC combo arrived I was unprepared for the subjective improvement it made on my system. I'd been using a couple of different tube amps (home made and commercial) along with a Japanese integrated amplifier of good quality, rated at 100/ch. The Benchmark combination was like lifting a haze over my speakers. I have fairly sensitive horn speakers (Paul Klipsch La Scala II) and now am listening to them at a much too loud level. I have to remind myself to turn them down. I attribute it to the very low distortion the amp and DAC produce. La Scalas are known to be 'bass deficient', and it is true as far as it goes, but with this amplifier the bass is tight, overall imaging is rock solid, and highs are not harsh at all (of course a bad recording will always sound bad).

Build quality and fit/finish appears to be excellent. The small form factor is shocking, considering the usual thing out there. I ordered the Benchmark speaker cables, which were reasonably priced, and quite well built. Not the typical snake oil magic wire thing. But you need them for the SpeakOn side, and the expanding banana plugs were quite ergonomic, too.

My final word is that unless you need a lot more power for your particular application, there is not much need to spend more than five large for any DAC/amp combination. If you do need more power, buy two AHB amps. That is that.

PS: as far as the on/off switch? Use the amp's 12volt trigger line into the DAC, and turn the entire system on with the remote.

The speaker cables are just Canare RS411 terminated in speakon connectors at the amp end. You can buy them for half Benchmark's price at B&H,buy some speakons for $10 and reterminate them yourself in 10 minutes and have the exact same thing for half of Benchmark's asking price.

 

[phoenixdogfan]

The new Purifi Eigentakt 1E400A should have THD a little better than the Hypex nCore NC400, but IMD better than the AHB2. Let's see.
https://cdn.computeraudiophile.com/article-images/2019/0517/1ET400A - Product Brief (1.01).pdf

I wish Benchmark had a more powerful version of this amplifier using the same technology, like 600-700W in 4 ohms stable for example.

Could a Hypex Power supply be used and these modules be subbed for NC400s?

 

[phoenixdogfan]

What I like about the brand and the products themselves, is they let the gear speak for itself.

In a previous thread, we looked at the interior shots and found nothing of significance to complain about- it's a glorious looking design.

Also nice to see a currently available reasonably priced product that puts paid to the hype, surrounding Hypex. "Ncore® is the first Class-D amplifier not just to nudge the best linear amplifiers, but to surpass them in every aspect relevant to sound quality."

@amirm Did you precondition the Benchmark for an hour and have you run the full power tests for 5 minutes?

I'm building the HYpex MC400 stereo. My all-in cost will be less than $1100 USD. Seems like a worthy trade off for a slightly less good 105db vs 112 db Sinad.

 

[RayDunzl]

If your wires are only 1.5 m long, there is not issue. At this length, you can get away with just about anything. The inductance will be too low to matter.

Yeah... that was my eyeball estimate...

Though I did measure (in room) a little more HF using the fat wires vs 18AWG twisted magnet wire (too thin) - which I put down to less resistance - low speaker ohms at the high frequency limit (electrostats) would draw a fair bit of current (a boatload of electrons, anyway).

Nevertheless, check your numbers: I doubt that the conductors are just 8mm apart given the fact that the conductor diameter is 7.35 mm. This implies that the insulation is 0.35mm thick (which is very thin).

Oh... Mistake. I should be measuring from the center of the conductor.

Now I see that on the calculation diagram below.

Ok:

Wire spec

Conductor diameter - 7.264mm
Insulation/Jacket thickness - 1.168mm
Minimal Spacing (tight) - 9.6mm

0.000000475 H


Then, loose spacing - say, 26mm... an inch.

Inductance: 0.00000118 H 11.8e-7 H

Almost 3x more with loose spacing.

*scratches head again, wonders how much is a lot... declines further calculations at the moment....


----

 

[Matias]

Could a Hypex Power supply be used and these modules be subbed for NC400s?

I don't know, we will have to wait and see from Purifi.

 

[John_Siau]

20 uH into a 4-Ohm load will be 3 dB down at 32 kHz. This will be 1.5 dB down at 20 kHz. Your inductance is much less than this (even when using the wide spacing). You calculated 1 uH for a 1.5 m length. At 30 m you would reach 20 uH and you may (or may not) begin to notice the high-frequency roll off (-1.5 dB at 20 kHz). The large diameter of your conductors is helping to reduce the inductance.

Here is a tool for calculating the response:

http://sim.okawa-denshi.jp/en/LRtool.php

 

[gvl]

https://www.stereophile.com/content/nothing-what-i-want:

Good read. I used to enjoy NOS DAC sound. It all fell apart when I tried to play some violin music. The violins sounded like mush. That BP contraption a.k.a. DAC is a joke and a rip-off. Apart from a 16-bit budget obsolete DAC part (and claimed 24-bit compatibility), why would anyone want to use a tube-rectifier, part-time, in a DAC?

 

[gvl]

Thanks for posting the photo. The problem with this setup will be inductance. Inductance increases when the spacing between the conductors increases. The large conductors provide a low series resistance, but the spacing creates a large inductance in series with the speakers. This inductance creates a low-pass l-r filter which will roll off the high frequencies. Your solution is excellent for sub woofer applications but will cause some attenuation of high frequencies. It will also cause a phase shift that will delay the high frequencies.
...

Wouldn't the wires that run closer introduce increased capacitance leading to a similar detriment?

I have some vintage 10AWG Monster speaker cable I planned to utilize, it must have awful inductance, but as I recently found I'm now deaf above 14kHz I should have little reason to worry about it.

 

[restorer-john]

If this is based on a THX design, lets hope some chinese like Topping or Smsl can build their more affordable version

I'm sorry, this type of comment I simply don't understand or agree with.

We have a company producing a world class product in the US, using proprietary technology, high quality componentry and construction techniques, all put together by local labour at a price that is extremely competitive for the performance offered.

And you want a cheap Chinese copy?

 

[gvl]

Those who work minimum wage here in the US have to work 5 weeks to come up with this amount. Not eating and sleeping under the bridge. And not paying income taxes. Just to give a perspective.

 

[RichB]

Nice, Amir. This is one of a few and now at the top of my list should I ever upgrade amps.

These have been crossed off my list. I bought 4 and love them.

- Rich

 

[digitalfrost]

But perfect amplifier? No. It excels in steady state measurements, but it isn't as dynamic sounding as other good amplifiers with which I've compared it. Again, this isn't a question of steady state measurements or amplifier power -- I'm not clipping it. But listen to a piano on the Benchmark and another good amp and you'll hear what I mean: it rounds off the attack.

[...]

So the Benchmark isn't a perfect amplifier, but anyone who has never heard a really good amplifier or thinks that all amps sound the same is going to be blown away by the sound. It's a bargain, too, by the standards of high end amplifiers, and with its sophisticated protection circuitry, quite bulletproof!

I have a love for the big amplifiers made at the end of the 80s. Specifically the Sony ES series. I like the soundstage, and the way in which they make me able to hear the air between the instruments. You can almost touch it. They place another acoustical room inside your room. Alas, my 30 year old amplifier is currently broken, again and I'm looking for something more reliable.

Given your experience with the AHB2, do you think it would be good fit for me?

For the last couple of days I've been going back and forth between the Hyper NC400 DIY modules, a boutique NC500 amp, the NAD M22 or the Benchmark. I'm quite disappointed the tech specs of most current amplifiers, when I compare them with what was possible 30 years ago, it's often a joke what you get today.

 

[gvl]

If you have the $$$ and like clean sound then Benchmark seems like a no brainer considering the performance and long-term support should anything go wrong.

 

[anmpr1]

The speaker cables are just Canare RS411 terminated in speakon connectors at the amp end. You can buy them for half Benchmark's price at B&H,buy some speakons for $10 and reterminate them yourself in 10 minutes and have the exact same thing for half of Benchmark's asking price.

If I spend 5 large for the package, I'm not quibbling over the price of their speaker cable. Your suggestion reminds me of someone going to a fancy restaurant, and bringing their own bottled water to drink because it's cheaper than the Perrier. Sorry, at my age I've put away my soldering iron. Go for it, if you like.

 

[gvl]

If I spend 5 large for the package, I'm not quibbling over the price of their speaker cable. Your suggestion reminds me of someone going to a fancy restaurant, and bringing their own bottled water to drink because it's cheaper than the Perrier. Sorry, at my age I've put away my soldering iron. Go for it, if you like.

Agree. But, you could also get that package and also have a nice meal at that fancy restaurant sipping Perrier for the same amount.

 

[restorer-john]

Those who work minimum wage here in the US have to work 5 weeks to come up with this amount. Not eating and sleeping under the bridge. And not paying income taxes. Just to give a perspective.

Oh come on. High Fidelity was originally an expensive hobby for people with significant means and electronics skills. It was not for everyone.

It was democratized massively in the late 60s through mid 70s, and commoditized by the mid 80s. But, the best performing gear was always expensive, incredibly well built, and not something a minimum wage person could, or should be aspiring to.

Now you can pick up Chinese rubbish in pretty anodized cans masquerading as something special, but don't kid yourself, it's not in the same league. It's just cheap, cheerful and disposable, something that will become increasingly less acceptable as we move towards a sustainable (ie keeping things alive) world.

 

[gvl]

Oh come on. High Fidelity was originally an expensive hobby for people with significant means and electronics skills. It was not for everyone.

It was democratized massively in the late 60s through mid 70s, and commoditized by the mid 80s. But, the best performing gear was always expensive, incredibly well built, and not something a minimum wage person could, or should be aspiring to.

Now you can pick up Chinese rubbish in pretty anodized cans masquerading as something special, but don't kid yourself, it's not in the same league. It's just cheap, cheerful and disposable, something that will become increasingly less acceptable as we move towards a sustainable (ie keeping things alive) world.

I was not picking sides, I was just providing a perspective. If anything, I'm on your side, but those less fortunate should have options.

 

[estuardo4]

I have a love for the big amplifiers made at the end of the 80s. Specifically the Sony ES series. I like the soundstage, and the way in which they make me able to hear the air between the instruments. You can almost touch it. They place another acoustical room inside your room. Alas, my 30 year old amplifier is currently broken, again and I'm looking for something more reliable.

Given your experience with the AHB2, do you think it would be good fit for me?

For the last couple of days I've been going back and forth between the Hyper NC400 DIY modules, a boutique NC500 amp, the NAD M22 or the Benchmark. I'm quite disappointed the tech specs of most current amplifiers, when I compare them with what was possible 30 years ago, it's often a joke what you get today.

It is not a joke, you are paying less and less money for less electricity use, less heat, less hum, and less distortion. I don't want to part with my B&K power amp, but I'm happy using a Class D amp knowing that I have almost the same sound I like for less money.

This is something that I don't understand from some people on this forum. On one hand, you have lots of people saying that we are living in the golden age of Stereo reproduction, and on the other , you have several that says that old technology was the best and today all is a joke.

 

[restorer-john]

This is something that I don't understand from some people on this forum. On one hand, you have lots of people saying that we are living in the golden age of Stereo reproduction, and on the other , you have several that says that old technology was the best and today all is a joke.

Isn't that the way it is with all forums?

Old geezers yelling out "get off my lawn", young idealists with no money and no idea, engineers, theorists, marketeers, retired military guys, disillusioned industry executives, manufacturers, and washed up salesmen. It's a wonder it works at all...

 

[estuardo4]

Isn't that the way it is with all forums?

Old geezers yelling out "get off my lawn", young idealists with no money and no idea, engineers, theorists, marketeers, retired military guys, disillusioned industry executives, manufacturers, and washed up salesmen. It's a wonder it works at all...

I guess you are right. Or maybe not...