Review and Measurements of Benchmark AHB2 Amp

[Xulonn]

Even some sellers admit it.

LOL - your example of a reseller/marketer (Audiophonics) who warns about noise in one of their el-cheapo products, is a company that features Audio-GD products at the top of their listing of power amplifiers - with no warnings about possible quality issues. (Of course, Audio-GD may have chosen to limit their lousy engineering to their DACs and apply sound engineering (pun intended) to their amplifiers - but I doubt it.

After testing two Audio-GD DACs and a DAC/amp, Amir had this to say: (I'm sure he would allow Audiophonics to quote his words.)

Needless to say, my advice remains to avoid purchasing these Audio-gd products. They are antithesis to what it means to be an "audiophile." That word better have some meaning left it in.

 

[blueone]

But if the power amp is causing the hiss or buzz or whatever noise, this is obvious in measurements.

That's why I suspect it could be a gain issue between components in the signal path, because I agree in principle that if it's the amp it would show up in the SNR measurement. The hissing that RichB was referring to is pretty low in level; you normally have to put your ear within inches of the tweeter to hear it, though I did hear an example once where you could perceive it in a quiet room standing a couple of feet away from the speaker.

I've noticed over the past several years that power amplifiers vary in gain more than I remember long ago, like from 25db to 34db, and some line-level source components I've run into (or own) have what seem like unusually high or low output levels (especially on single-ended outputs). For example, a couple of Sony Bluray players I've owned seem to have curiously low output levels. So I've wondered if these widely varying gain levels are the issue.

 

[RichB]

Those issues may or may not be related to the power amp (other than transformer buzz). That's something you'll have to track down. You may have some issues with your sources, no way for me to tell remotely.

No doubt equipment and environmental related.
However, there are products that are more susceptible to environmental issues than others.
One manufacturer hand-wound transformers for me that were significantly quieter than other stock versions of the same model.

Susceptibility to environmental influences are not tested and like speaker load are difficult to establish a representative baseline.
There are aspects beyond SINAD worthy of consideration.

- Rich

 

[RichB]

That's why I suspect it could be a gain issue between components in the signal path, because I agree in principle that if it's the amp it would show up in the SNR measurement. The hissing that RichB was referring to is pretty low in level; you normally have to put your ear within inches of the tweeter to hear it, though I did hear an example once where you could perceive it in a quiet room standing a couple of feet away from the speaker.

I've noticed over the past several years that power amplifiers vary in gain more than I remember long ago, like from 25db to 34db, and some line-level source components I've run into (or own) have what seem like unusually high or low output levels (especially on single-ended outputs). For example, a couple of Sony Bluray players I've owned seem to have curiously low output levels. So I've wondered if these widely varying gain levels are the issue.

Hissing has been at a low level. Buzz and transformer hum were audible from my seating position.

The Marantz 8801 was on case where balanced cables helped removed hissing even though unit is not balanced.
This unit did hiss very loudly due to a faulty loose power receptacle which I discovered we the cord was pushed slightly ajar. The hiss was quite loud. This resulted in a second repair of this unit by United Radio for the second failed/smoked trigger and this time the replacement power receptacle. Marantz has reportedly improved the trigger design in the 8805 and other models.

Hissing is a big deal for those with efficient speakers. Of course, SINAD and other measurements provide the data required to select a suitable amplifier.

- Rich

 

[daftcombo]

LOL - your example of a reseller/marketer (Audiophonics) who warns about noise in one of their el-cheapo products, is a company that features Audio-GD products at the top of their listing of power amplifiers - with no warnings about possible quality issues. (Of course, Audio-GD may have chosen to limit their lousy engineering to their DACs and apply sound engineering (pun intended) to their amplifiers - but I doubt it.

After testing two Audio-GD DACs and a DAC/amp, Amir had this to say: (I'm sure he would allow Audiophonics to quote his words.)

They also sell all Topping DACs and Hypex amps. Not a lot of small companies sell those.
The warning appeared after buyer complains to those specific products. What is so LOL about that? Not a lot of companies would do that.
They even link to ASR reviews!! Example: https://www.audiophonics.fr/en/dac-...plifier-bluetooth-apt-x-hd-black-p-13453.html

I have no doubt about Audio-GD measuring bad and probably sounding not hi-fi at all though.

 

[kazsud]

What are the chances of a mkii version or new amp all together? Since this came out so long ago.

 

[Xulonn]

They also sell all Topping DACs and Hypex amps. Not a lot of small companies sell those.
The warning appeared after buyer complains to those specific products. What is so LOL about that?

Just laughing at the irony. I have an overall positive impression of Audiophonics from being familiar with their website, and would not hesitate to buy from them. However, their featuring of Audio-GD as implied high-fidelity products reinforces my belief in checking, as always, for third-party opinions here at ASR or elsewhere.

Audiophonics carries an impressive lineup of audio gear, and they have some very good prices on Hypex and ICEpower amps, including a house-brand assembled Hypex Ncore balanced power amp for $350US. They also sell - as you noted - some of the better Chi-Fi products, such as Topping. SMSL and FX Audio.

 

[digitalfrost]

Audiophonics carries an impressive lineup of audio gear, and they have some very good prices on Hypex and ICEpower amps, including a house-brand assembled Hypex Ncore balanced power amp for $350US. They also sell - as you noted - some of the better Chi-Fi products, such as Topping. SMSL and FX Audio.

I am very happy with them. They are a european source for a lot of the gear that is discussed in international forums, be it equipment from china or the US. They have most of it in stock, so I don't have to wait 2 weeks for stuff to arrive and I don't have to deal with customs either.

 

[amirm]

I know. But you can't guarantee that a certain individual would prefer absolute fidelity to a device which somehow makes sound things nicer (at least to personal criteria).

In electronics/amplifiers I have NOT found that option to exist, not matter how much it is taken for granted. Distortions either are inaudible or make the music less pleasant.

So please don't assume the common defense that "this amp has high measured distortion but sounds warm, has wider soundstage, etc." ALL of those results are uncontrolled, and unreliable observations. This has become so prevalent that objectivists often accept them as explanation.

Now maybe one day I find such a device (measures bad, sounds good) but even if that happens, it shows that it is a very rare thing, not common at all.

Net, net, don't use unreliable data/assumptions to drive at factual conclusions.

 

[amirm]

LOL - your example of a reseller/marketer (Audiophonics) who warns about noise in one of their el-cheapo products, is a company that features Audio-GD products at the top of their listing of power amplifiers - with no warnings about possible quality issues.

Audiophonics links to our site and we get fair bit of traffic from them. As such, I consider them one of the "good retailers," not the enemy. Ultimately they sell what their customers are asking about. I can't blame them for that.

 

[zalive]

This discussion parallels the one on cables.

The cable industry frequently advises that cables be used for a number of hours of "burn in time". Metallurgists and scientists know that, at the voltages and currents used in the audio industry, the notion of changes occurring in the physical or electrical properties of copper wire is utter bunk.

The real issue is psychoacoustic, where the brain requires time to hear what it wants to hear. I think the same thing applies to source material, playback devices, amplifiers, and loudspeakers.

So how is this for an idea: We accept the objective measurement of devices. We audition devices meeting certain performance thresholds (20-20 kHz +/- 0.5 dB, THD+N under -116 dB, etc.). Provided an audition falls within a broadly acceptable range of performance, we then allow our ears to burn-in.

Musicians would call this training one's ear to recognize certain tones, pitches, rhythms. We might call it training ourselves to be objectively better consumers.

I really hope some light will be shed within a reasonable period over cables, in a scientific way.
Cable manufacturers claim it's not the metal that needs the burn-in, but dielectric.
Their general explanation on how dielectric (outside of burn-in time issue) affects the signal is charge-discharge cycle: dielectric charges from the signal from the conductor, then discharges back to the conductor, but with some time delay. Some describe it as a time smear. I imagine it as an echo from the signal.

So to determine whether this is true or not, I'd say we need a specifically designed measurement. Discharge from the dielectric won't supposedly generate harmonic or non-harmonic distortion because it follows the original frequency. Instead, distortion supposedly happens in the time domain only - time delayed artifacts instead of changed artifacts.

So I guess cable measurement designed to prove or disprove whether something like this happens should use something like a signal impulse of a very short duration and then screen whether it generates additional waveform (of a same frequency) in time domain, trailing the original signal impulse.

I point out, these are only my own thoughts/speculations on how the truth about this should be experimentally researched, based on what sounds logical to me.

 

[SIY]

I point out, these are only my own thoughts/speculations on how the truth about this should be experimentally researched, based on what sounds logical to me.

Think of all the modern technology that wouldn't work if this were true.

Then think of the evidentiary support from the scam artists peddling this (i.e., none at all).

Then go worry about something else.

 

[amirm]

I point out, these are only my own thoughts/speculations on how the truth about this should be experimentally researched, based on what sounds logical to me.

As long as the effect is not there (measurable change), there is no reason to search for supposed cause. On the other hand, companies who state these theories should attach measurements to them. Until then, it is a marketing strategy, not science and engineering.

 

[zalive]

In electronics/amplifiers I have NOT found that option to exist, not matter how much it is taken for granted. Distortions either are inaudible or make the music less pleasant.

So please don't assume the common defense that "this amp has high measured distortion but sounds warm, has wider soundstage, etc." ALL of those results are uncontrolled, and unreliable observations. This has become so prevalent that objectivists often accept them as explanation.

Now maybe one day I find such a device (measures bad, sounds good) but even if that happens, it shows that it is a very rare thing, not common at all.

Net, net, don't use unreliable data/assumptions to drive at factual conclusions.

So how do you explain a number of audiophiles who usually prefer tube designs sound?
There should be a scientistic research blind test proof on 'listeners prefer listening to gear which objectively measures better' to accept this as a fact.

 

[SIY]

So how do you explain a number of audiophiles who usually prefer tube designs sound?
There should be a scientistic research blind test proof on 'listeners prefer listening to gear which objectively measures better' to accept this as a fact.

Don't hold your breath waiting for the people making that claim to actually back it up with evidence.

 

[restorer-john]

but certainly reviews at the late great Audio Critic and my current magazine note things like mechanical noises.

Transformer noise is a huge one. I've had many amplifiers exhibiting otherwise excellent performance let down by a physical noise floor you can hear across the room. I saw in a recent post, you also have an amplifier unused in a cupboard for that very reason.

 

[zalive]

Think of all the modern technology that wouldn't work if this were true.

Explain what wouldn't work and why.

As long as the effect is not there (measurable change), there is no reason to search for supposed cause. On the other hand, companies who state these theories should attach measurements to them. Until then, it is a marketing strategy, not science and engineering.

Who says it isn't there? You can't diagnose it using incorrectly designed measurements (for the purpose) which don't detect it. Time domain distortions require different methodology to detect it. Until this is proven or disproved it's just assumptions on both ends.

 

[SIY]

Explain what wouldn't work and why.

I'll even invoke Hillel and do it standing on one foot.

Just remember, using non-voodoo engineering, we can send data back and forth to space probes in the outer solar system. We can count individual photons. MRI. Cell phones. LIGO. Every electronic device you commonly use.

Time domain distortions require different methodology to detect it.

No.

 

[zalive]

No.

It's supposed to be of the same frequency as the signal. If you don't screen the time domain you can't see such in a graph, signal wave overshadows it.

 

[amirm]

Who says it isn't there? You can't diagnose it using incorrectly designed measurements (for the purpose) which don't detect it. Time domain distortions require different methodology to detect it. Until this is proven or disproved it's just assumptions on both ends.

Ah, the "time domain." Why did you not say that before? I could have dismissed the case even sooner.

Who says anything is happening in time domain? And how such a thing would not impact every measurement we are making?

Answer is simple: nothing is happening in time domain. If you think there is, then develop the test and demonstrate it. It is not our job to chase ghosts and made up hypothesis by people who don't know the engineering, measurements, math and science.

Remember, the audible effect is simply not there in controlled testing. So before you even jump into measurements, conduct a controlled test and show that it is audible then I will be the first one to jump on finding out why.