Benchmark AHB2 Review (Updated Measurements)

[kyuu]

Has anyone tried it with a tube pre-amp which is supposedly giving a warmer sound?

Why in the world would you pay a lot of money for an amp that's this transparent just to trash it with a tube pre-amp? Just buy a much cheaper tube amp to color your sound. Or any old amp and use some EQ to get the colored sound you're after.

 

[Julf]

Why in the world would you pay a lot of money for an amp that's this transparent just to trash it with a tube pre-amp? Just buy a much cheaper tube amp to color your sound. Or any old amp and use some EQ to get the colored sound you're after.

Or go DSP.

TAP TubeWarmth plugin
Tube Saturator Vintage

 

[HappyCow]

Just saying might be the cheaper option vs getting new amps

In any case for my own comparison vs ML 5302 I'm doing with and without Dirac Live. Maybe Dirac DSP will remove some of that old school AB warmth.

So far jazz and classic sounds fabulous with AHB2 but for electronic and metal I think the 5302 has a slight edge. Maybe I'm just old school and prefer some coloration :/

 

[SIY]

Has anyone tried it with a tube pre-amp which is supposedly giving a warmer sound?

Key word is “supposedly.” The belief machine is a powerful one.

 

[Chr1]

Once again amusing to see how, within just a couple of posts tube amps are: both, derided for adding warmth...
Then moments later, the same folks question whether they actually do this or not...
Bizarre. Just my 2c.

 

[gfinlays]

I see that many people have found AHB2 as flat, less emotional, less engaging amplifier (when it measures perfect). Could it be due to some, phase/time smear happening at different frequencies, which they are more sensitive too? After reading many posts across many threads, I feel as if AHB2 is performing like perfect CD sound of early 80’s; which was measuring perfect compared to LPs but with anecdotal observations of being flat, less emotional, less engaging. Later, it was blamed on filters, jitter, impulse response, oversampling… all that stuff that was either not measured at that time or not thought to be important to the sound quality.

In the video, at time 10:01, as I understand, using low pass and high pass filters, AHB2 uses feedback at lower frequencies and feedforward at higher frequencies

.
All filters have consequences. Is there something happening to phase across audio band? Nonlinear phase response? Group delay? Does the low pass and high pass filters are doing something which is not being measured but some people are picking up as flat sound or less engaging?

Group delay is measured for loudspeakers, why it is not part of standard set of amplifier measurements?

The AHB2 is utterly transparent and ruthlessly revealing. If someone is using a more "euphonic" sounding amplifier to "tame" their system, switching in an AHB2 is going to bring about unpleasant changes in the sound.

Though as has already been said, the anecdotal claims are never backed up with blind, level-matched listening tests.

For the audiophiles who predominantly listen with their eyes rather than their ears, the AHB2 just doesn't sit right with their biases. It doesn't have bling enough looks, and frankly isn't expensive enough to occupy the space in their racks. So they convince themselves it doesn't sound as good as other amps with better looks/higher price tag/more bragging rights. They also can't compute when a company eschews silly-expensive cables and hyperbolic word-salad descriptions of its products' capabilities.

Which is a shame really. The AHB2 is all the amp you'll ever need.

Need more power? Buy 2 and bridge them.

I love mine. Running a pair in bridged mono at the moment. Adding a third later and switching them to stereo to give me 6 channels for a fully active 3-way stereo pair. Just got to learn how to use Acourate, then do all the measurements and design the crossover filters!

 

[Pearljam5000]

I wonder how it compares to this beast

 

[Purité Audio]

Hoovering underneath will be much more convenient with the Benchmark.
Keith

 

[AdrianusG]

I wonder how it compares to this beast View attachment 391613View attachment 391614View attachment 391615

Pffff what a relieve, for a moment i thought that the price was for just 1
and for "convenience" they put it on spikes, great choice for something with this kinda weight

 

[gfinlays]

I wonder how it compares to this beast View attachment 391613View attachment 391614View attachment 391615

I haven't found measurements for the mono, but the measurements for the Stereo Apex aren't impressive given its price tag......

Edit: There was a previous thread about the mediocre measurements

 

[new2hifi]

Here you go. Although his own amplifiers were unimpressive in Stereophile's measurements (tubes!), but the Roger Gibboni has sound technical background and is making a case about Group Delay in amplifiers.

Analog amplifiers normally don’t use high/low pass filters on incoming signal, apply different corrections and then again sum the signal; AHB2 is doing that. I think Amir, Stereophile or even Benchmark guys should do the group delay measurement tests Mr. Gibboni is to taking about.



I have nothing against Benchmark AHB2 and I trust measurements. But I have heard weird devices making good clean sound (to ears) and vice versa. Thus, I suspect either something is not being measured because we still have not discovered it or we don’t deem it important yet.

Perhaps, like when solid state amplifiers came in 70’s and while they measured better than tube amplifiers, tube amplifiers had better sound as per ears. Then people blamed, feedback, lack of enough feedback, lack of pleasant second harmonics, higher order distortion, intermodulation distortion, unclean clipping behavior,…and now addressing all that has improved solid state amplifiers to the point where, as per listening (I don't want to use listening "tests"), they are better than 70's solid state amplifiers.

 

[SIY]

Here you go. Although his own amplifiers were unimpressive in Stereophile's measurements (tubes!), but the Roger Gibboni has sound technical background and is making a case about Group Delay in amplifiers.

Analog amplifiers normally don’t use high/low pass filters on incoming signal, apply different corrections and then again sum the signal; AHB2 is doing that. I think Amir, Stereophile or even Benchmark guys should do the group delay measurement tests Mr. Gibboni is to taking about.



I have nothing against Benchmark AHB2 and I trust measurements. But I have heard weird devices making good clean sound (to ears) and vice versa. Thus, I suspect either something is not being measured because we still have not discovered it or we don’t deem it important yet.

Perhaps, like when solid state amplifiers came in 70’s and while they measured better than tube amplifiers, tube amplifiers had better sound as per ears. Then people blamed, feedback, lack of enough feedback, lack of pleasant second harmonics, higher order distortion, intermodulation distortion, unclean clipping behavior,…and now addressing all that has improved solid state amplifiers to the point where, as per listening (I don't want to use listening "tests"), they are better than 70's solid state amplifiers.

He's fortunate that there wasn't anyone competent enough in the audience to call him on his bullshit. This is seriously transparent FUD aimed at the technically ignorant.

 

[SIY]

But I have heard weird devices making good clean sound (to ears) and vice versa. Thus, I suspect either something is not being measured because we still have not discovered it or we don’t deem it important yet.

Or it's in your brain, not in the sound waves. This isn't pejorative- ALL human brains work that way, which is why any sonic claims that are valid are arrived at using basic ears-only controls.

Trust your ears, distrust your lying brain.

 

[gfinlays]

Analog amplifiers normally don’t use high/low pass filters on incoming signal, apply different corrections and then again sum the signal; AHB2 is doing that.

I think you've misunderstood what the AHB2 does. It applies feed forward correction to eliminate distortion. There's no high/low pass filtering going on. The measurements speak for themselves. Have a read of Stereophile's review (subjective and measurements). Kal Rubinson owns a handful of AHB2s, paid for out of his own pocket.

There's nothing to be measured that we haven't discovered yet, though that doesn't stop the die-hard audiophools from positing those theories.

 

[Julf]

Here you go. Although his own amplifiers were unimpressive in Stereophile's measurements (tubes!), but the Roger Gibboni has sound technical background and is making a case about Group Delay in amplifiers.

Logical fallacies: appeal to authority

 

[new2hifi]

Or it's in your brain, not in the sound waves. This isn't pejorative- ALL human brains work that way, which is why any sonic claims that are valid are arrived at using basic ears-only controls.

Trust your ears, distrust your lying brain.

SIY, yup you are right, mind does play tricks and our prejudices control our perception. But it can go both ways. Thus, I cannot discount experiences of other people; there could be a scientific reason to that, a missing link. Isn't that what Floyd Toole did in his loudspeaker research? Using double blind tests and data, he found out that the off axis behavior of loudspeaker is also very important in people liking a loudspeaker. I suspect earlier that measure of performance was not that important.

 

[SIY]

Isn't that what Floyd Toole did in his loudspeaker research? Using double blind tests and data, he found out that the off axis behavior of loudspeaker is also very important in people liking a loudspeaker.

Yes he did. Toole’s work made known things (polar pattern matters) more rigorous and correlated better with controlled listening tests.

And unless a guy trying to sell stuff has done the same and documented it thoroughly, put your hand on your wallet. Especially when his claims don’t comport with a half a century of data and are surrounded with incorrect and misleading technical statements.

 

[DonH56]

"...our designs have zero group delay..."

To quote @SIY: uh-huh.

Also, large group delay does not smear the image if it is constant. He's mixing up a few things there. Changing group delay affects pulse response, not sure how much it takes to be audible. @j_j has discussed this and how much change there must be within an ERB (equivalent rectangular bandwidth) to be audible.

Curious what does the mixing in a guitar string that requires 200 kHz bandwidth from an amplifier. He implies it happens in the ear, but from what I recall that is well outside what the ear responds to (but am not a hearing guru or even very knowledgeable about the physiology).

I find it hard to believe any modern amplifier suffers from significant (audible) group delay variance. Speakers, sure...

 

[GXAlan]

@new2hifi

The other possibility is that people are accustomed to a certain level of distortion or coloration and the absence of it is what is problematic.

Sony’s TA-ZH1ES had the ability to introduce phase shift in the bass since they felt like it could make a difference to perceived sound and they felt like many Class AB headphone amps had it and their Class D headphone amp doesn’t. I thought the IMD from DSEE made a bigger difference.

It’s hard to do quick switching but I don’t remember it being that big of a difference.

DSEE HX is free to try. Just download Sony Music Center for the PC and play your FLACs.

 

[SIY]

"...our designs have zero group delay..."

To quote @SIY: uh-huh.

Also, large group delay does not smear the image if it is constant. He's mixing up a few things there. Changing group delay affects pulse response, not sure how much it takes to be audible. @j_j has discussed this and how much change there must be within an ERB (equivalent rectangular bandwidth) to be audible.

Curious what does the mixing in a guitar string that requires 200 kHz bandwidth from an amplifier. He implies it happens in the ear, but from what I recall that is well outside what the ear responds to (but am not a hearing guru or even very knowledgeable about the physiology).

I find it hard to believe any modern amplifier suffers from significant (audible) group delay variance. Speakers, sure...

Even if your amp goes to 200kHz, the mikes, recording gear, and speakers surely don’t. And the intermodulation claim is ludicrous, not just because of the levels in question, but also because intermod products in the audio band are trivially measurable.

What you have here is a standard issue fashion audio huckster.