WolfX700 Measurement of Benchmark AHB2 Power AMP

[anmpr1]

A) No doubt this is an excellent amplifier! Although it is not cheap in my opinion, considering that the price often increases exponentially with performance...

B) In fact, more than one Chinese manufacturer has stated that they are developing a power amplifier that is less than half the price of AHB2 and meets or exceeds its performance)

A) On an absolute level, the AHB2 is not an expensive amplifier. Given what is generally available in the 'high end' it is in fact a very cheap amplifier for what it offers.

B) When discussing manufacturing costs, we must always be cognizant of the 'cost' of doing business. In America, in New York state, the cost of business has to be significantly higher than, say, Shenzhen. Since most folks just look at the sales receipt, this intrinsic 'cost' is always hidden, and most do not consider it when assessing overall product value vis-a-vis retail price.

 

[WolfX-700]

A) On an absolute level, the AHB2 is not an expensive amplifier. Given what is generally available in the 'high end' it is in fact a very cheap amplifier for what it offers.

B) When discussing manufacturing costs, we must always be cognizant of the 'cost' of doing business. In America, in New York state, the cost of business has to be significantly higher than, say, Shenzhen. Since most folks just look at the sales receipt, this intrinsic 'cost' is always hidden, and most do not consider it when assessing overall product value vis-a-vis retail price.

You're right, AHB2 is a fairly cheap unit for so-called "high-end audio products". That's why I broke my own values and decided to buy it.

But for me personally, it is not very happy to spend so much money to buy a power amplifier-my value is that the cost of the power amplifier should be less than 20% of the price of the speaker.

 

[anmpr1]

But for me personally, it is not very happy to spend so much money to buy a power amplifier-my value is that the cost of the power amplifier should be less than 20% of the price of the speaker.

That is a good point. One has to establish their own value hierarchy. The only two reasons to spend money on an AHB2 are 1) because its tiny form factor is just down right cute and cuddly; 2) it is the best amplifier in the world, spec-wise. Perhaps another reason would be company support, but in China that has to be problematic.

Disclaimer--I own an AHB2. I bought it because it was the best, measurement-wise. Soon, whether in China or Malaysia or somewhere, someone will come out with a 'better' amplifier. At that time, we hope an AHB3 will be on the assembly lines. In the meantime, it is the last amplifier I will purchase.

 

[WolfX-700]

That is a good point. One has to establish their own value hierarchy. The only two reasons to spend money on an AHB2 are 1) because its tiny form factor is just down right cute and cuddly; 2) it is the best amplifier in the world, spec-wise. Perhaps another reason would be company support, but in China that has to be problematic.

Disclaimer--I own an AHB2. I bought it because it was the best, measurement-wise. Soon, whether in China or Malaysia or somewhere, someone will come out with a 'better' amplifier. At that time, we hope an AHB3 will be on the assembly lines. In the meantime, it is the last amplifier I will purchase.

It was because AHB2 had near-perfect measurement results (posted by Amir) that made me determined (albeit a bit difficult) to break through the PowerAmp price ceiling I set myself (about $ 1,000)

 

[VeerK]

Oh man, if there are some AHB2 alternatives on the horizon, I’m super excited. You’re giving me some hope here @WolfX-700 !

 

[restorer-john]

The Benchmark has excellent performance right up until it shuts down and that is hardly perfect is it? Again this unit shuts down at the low end and realistically there's no excuse for that. Run the test from LF to HF at full power and see what happens.

What power were you running on that test (it's not marked)? 180W@4R?

John Siau skirted around in the last AHB-2 review thread with excuses and hand waving, but none of it convinced me or others. It's over-zealous protection prevents the product reaching its rated specifications.

 

[WolfX-700]

The Benchmark has excellent performance right up until it shuts down and that is hardly perfect is it? Again this unit shuts down at the low end and realistically there's no excuse for that. Run the test from LF to HF at full power and see what happens.

What power were you running on that test (it's not marked)? 180W@4R?

John Siau skirted around in the last AHB-2 review thread with excuses and hand waving, but none of it convinced me or others. It's over-zealous protection prevents the product reaching its rated specifications.

Yes, the purple line (I actually marked it) is 180W @ 4R. This is a place that I am very puzzled or that I think does not meet the specifications-180W @ 4R should be within the specifications of the device, but it has activated the protection circuit.

I did it a few times to make sure it wasn't an accidental problem-it was the same every time.

 

[Wes]

Thank a lot for the review and a few more metrics tested Wolfman! Also nice to see more images

I got into audio a year and a half ago or so. I saw this amp reviewed, and looked up the company and the product, and realized it was the thing that brought THX to the consumer fore-front. We've now had headphone amps that have made THX a serious name, while also others like Geshelli and JDS proving they can make perhaps an even cleaner amp without their feed-forward error correction approach perhaps (unless they are also doing it themselves in a custom manner).

One thing I simply do not understand is, seeing as how this power amp was being shown off nearly half a decade ago. Why not a single contender has shown interest in surpassing it, or if they have, they've failed in some fashion or another. Is the scaling of the typical power usage that power amplifiers are made for, simply something that doesn't scale very well with the massive fidelity disparage between them, and headphone amps? I understand it plays a factor, but is the factor THIS BIG where for essentially half a decade no one has been able to dethrone this Rolex of the amplifier world?

I have never seen a piece of electronics maintain it's supremecy for this long, especially considering no newer SKU's or revisions of it were ever released(aside from blacked-out front plate).

But more interestingly, how hasn't anyone used the THX tech in any other power amp? We have multiple in other types of amps, heck even in mobile DAP devices now as well. But power amps, it seems just this only one, for some reason.

Benchmark has an exclusive license with THX - no copies until it expires

 

[Tks]

Benchmark has an exclusive license with THX - no copies until it expires

License for what? The modules themselves are purchasable last I saw. Also when does this license expire anyway? Also, what do you mean copies? No one is asking for Benchmark's schematics >_>

 

[Wes]

THX designed the feedforward circuit that reduces crossover distortion (from A to B) - it is protected IP

 

[Rja4000]

I'm a bit surprised at the large difference of -89.5db versus -108db THD+N at 1W.

The multitone level for each frequency is much lower than the single frequency sine.
The sum of all the peaks should be at the same specified level than the single frequency peak, so obviously, each peak is much lower.

How much so depends on the used multitone signal's specific Crest factor
For a 32 freq log signal, it's above 12dB for sure.

 

[lszomb]

Thanks for this. I am currently debating on buying an ABH2 to drive ATC SCM20psl or just buying a pair of SCM20asl. If I went beyond 20 for ATC, I would go for active for sure.

 

[boXem]

License for what? The modules themselves are purchasable last I saw. Also when does this license expire anyway? Also, what do you mean copies? No one is asking for Benchmark's schematics >_>

Where did you see that amp modules could be purchased?
As far as I understood, THX is licensing their patent(s) and provide reference designs for low power stuff like headamps.

 

[Tks]

THX designed the feedforward circuit that reduces crossover distortion (from A to B) - it is protected IP

This is a bog standard reply, doesn’t really answer my questions adequately.

Where did you see that amp modules could be purchased?
As far as I understood, THX is licensing their patent(s) and provide reference designs for low power stuff like headamps.

Which is why I asked the questions I ask. You said it yourself, they provide reference modules to be used in various devices. Their highest spec offering doesn’t seem to only mean headphone amp implementations. Lastly their whole patent notion on the matter seems very ambiguous, I never managed to find what that patent actually is, seeing as how tear-downs revealed no custom parts, just seemingly their own discrete configuration that could technically be copied without much issue I presume (though I’m not sure completely). As for feedforward error correction, this is tech older than the Second World War when I looked into it as opposed to negative feedback designs.

My point is, if there are companies already making use of their tech (obviously they pay THX for the right to use their name), it’s just puzzling why non power amp design has come out of it as well in half a decade. I doubt it’s a cost issue.

 

[Frank Dernie]

my value is that the cost of the power amplifier should be less than 20% of the price of the speaker.

And the DAC/ preamp half of that at most? So 10% of the speaker cost?

 

[Frank Dernie]

The Benchmark has excellent performance right up until it shuts down and that is hardly perfect is it? Again this unit shuts down at the low end and realistically there's no excuse for that. Run the test from LF to HF at full power and see what happens.

I tend to agree. It is only in the low end one needs all the power IME. look at the spectrum of any recording.

 

[Frank Dernie]

THX designed the feedforward circuit that reduces crossover distortion (from A to B) - it is protected IP

Yes but I remember a BBC programme about Chinese companies making copies and as part of it a Chinese Government spokeswoman was interviewed.
"Ah!" she said, "in the West you have copyright, in China we have the right to copy" That was the end of it. It was several years ago but if that is the official line there will be copies sooner or later.

 

[JohnYang1997]

Yes but I remember a BBC programme about Chinese companies making copies and as part of it a Chinese Government spokeswoman was interviewed.
"Ah!" she said, "in the West you have copyright, in China we have the right to copy" That was the end of it. It was several years ago but if that is the official line there will be copies sooner or later.

Chinese won't copy THX AAA circuitry because it doesn't require the patent circuit make just as good if not better performance.

 

[Frank Dernie]

Chinese won't copy THX AAA circuitry because it doesn't require the patent circuit make just as good if not better performance.

Actually the point at issue in the programme was copying the styling and packaging of a well known brand, and probably not the internals, since the problem had been a company going bankrupt due to a sudden increase in warranty claims which turned out to be Chinese copies being sold through some of their official suppliers who had, equally dishonestly, sourced them illegally and sold them as the real thing at full price.

 

[boXem]

Which is why I asked the questions I ask. You said it yourself, they provide reference modules to be used in various devices.

I said they provide designs, not modules. Hypex or Purifi provide modules implementing their IP. Designs are paper, modules are hardware. It means that the user of the design has to implement, test, debug, ... and doesn't benefit from the volume effect when sharing the module with other. So not simple and expensive.

Their highest spec offering doesn’t seem to only mean headphone amp implementations.

Rails at +/- 18V => max theoretical power in 8 Ohms is 5W.

Lastly their whole patent notion on the matter seems very ambiguous, I never managed to find what that patent actually is, seeing as how tear-downs revealed no custom parts, just seemingly their own discrete configuration that could technically be copied without much issue I presume (though I’m not sure completely). As for feedforward error correction, this is tech older than the Second World War when I looked into it as opposed to negative feedback designs.

https://patents.google.com/patent/US8004355B2/en, chapter "claims". It's a pain in the @ss to read, but this is where everything is.
All the art of patent is finding the little detail that makes a process, an assembly, a method, new. Not related to custom parts. The patent went trough the EPO process, which usually is much more stringent than US or Australia, so I guess there are some novelties. If not, I am surprised nobody tried to invalidate the patent.

My point is, if there are companies already making use of their tech (obviously they pay THX for the right to use their name), it’s just puzzling why non power amp design has come out of it as well in half a decade. I doubt it’s a cost issue.

You are mixing patents and trademarks. THX will sue companies using EPO patent 2401811 without licensing the same way they will sue the ones using the THX AAA trademark without licensing.
Cost drives 99% of business decisions. For the remaining 1%, @Wes provided a valid hypothesis (exclusive license).