Review and Measurements of Benchmark AHB2 Amp

[Sal1950]

I played on a small set of speakers, with a Maratnz PM-80 MKII SE wit ha few friends, while trying out different equipment. We then tried the AHB2 with an old high end Denon pre amp - cant remember the details of it. But the Benchmark started clipping easily, before we found out that you need to adjust the load on the rear. But still, there was no real improvement in sound. Maybe the Denon was not up to the job. But maybe, sometimes even good specs, does not equal better sound.

Yep, your correct. Your stellar golden ears have dug out the sonic failings of the AHB2. We will amend our high recommedation and warn all interested parties that the amp really falls down under expert subjective listening tests. Thank you for your contributions.

 

[Deleted member 2944]

2 way home made - SB drivers
DAP 2500
Fairly loud, but clipping started early. Never heard it like this before on any amp.

I know it's not a fair test. I just noted that rather old analog gear sounded fine in comparison with the Benchmark. We have no measurements to prove anything and I myself is a firm believer in specs and good theoretical corrects designs. But for some reason I expected something magical from the AHB2 - from all the reviews - even though I know they are mostly flawed. Maybe the old DAP 2500 is inferior in this situation.

Clearly you didn't understand how to set up the amplifier. The voltage gain of this amplifier is somewhat low even in the high gain position.
With a small set of speakers you certainly weren't clipping this power amplifier. Most likely you were clipping your preamp.

Dave.

 

[cbnbmore]

Something sounds a bit off as the Denon 2500 has a 2V output on the balanced output. Seems strange that the AHB2 would clip with such a low input voltage unless I'm missing something.......

 

[Sal1950]

Clearly you didn't understand how to set up the amplifier. .

RTFM ???

 

[Soniclife]

2 way home made - SB drivers
DAP 2500
Fairly loud, but clipping started early. Never heard it like this before on any amp.

I know it's not a fair test. I just noted that rather old analog gear sounded fine in comparison with the Benchmark. We have no measurements to prove anything and I myself is a firm believer in specs and good theoretical corrects designs. But for some reason I expected something magical from the AHB2 - from all the reviews - even though I know they are mostly flawed. Maybe the old DAP 2500 is inferior in this situation.

Was the clipping light coming on?

 

[etc6849]

The pre-amp is definitely a limiting factor (could be other things too like background noise, less sensitive speakers, etc...). You need one of the top 5 or so DACs measured here to hear the difference with this amp, and even then I'd still go with one offering a pro audio level pre-out. Hook it to a Benchmark DAC3 and then let us know if you hear a difference

In all seriousness, the entire signal chain is only as good as the weakest link. I have very sensitive speakers, so the difference with top quality pro audio gear is night and day to me. Personally, I would want every part of my playback chain to be capable of the best possible dynamic range, and the measurements shown here definitely show that this amp fits my goal. If there are no measurements for a piece of gear, I don't even consider buying it.

Also, the right measurements equals better sound. I can see why someone would say that if it was the 1970's, but measurement equipment has come a long ways and engineers do know what to measure. It's just big financial conglomerates keep buying companies (D&M) and are only in it for the money. They produce stuff over seas as cheap as possible and don't seem to spend the money on R&D or proper test equipment (D&M).

I played on a small set of speakers, with a Maratnz PM-80 MKII SE wit ha few friends, while trying out different equipment. We then tried the AHB2 with an old high end Denon pre amp - cant remember the details of it. But the Benchmark started clipping easily, before we found out that you need to adjust the load on the rear. But still, there was no real improvement in sound. Maybe the Denon was not up to the job. But maybe, sometimes even good specs, does not equal better sound.

 

[STUDIO51]

Standards are important. And the reason for its existence is to follow . But standards are not always absolute. Because standards are always walk slow for reliability. I am working as an audio measurement critic. I have measured the headphone jack performance of Samsung Galaxy and LG smartphones. Since this is a kind of digital-based device, I tried to measure the AES-17 with a few modifications.. However, I have experienced difficult in measuring the load test, and in particular the output impedance measurement has come up with an unreliable value.

Later, in recent smartphones, there is a solution that detect the resistance value at the chip and codec level. This is for to protect the consumer's ear. It was established as the EN-50332 standard. The smartphone searches for the resistance value and recognizes whether the connected device is a line-out, an in-ear headphone or a headphone. And according to the detect result, maximum output is limited to 1Vrms in lineout, 400mVrms in-ear headphone, and 2Vrms in headphone.


Therefore, the actual performance of this unit can not be measured with normal measurement. In order to measure the output impedance, it is necessary to try no-load measurement and load measurement, but the smartphone recognizes the no-load measurement and the load measurement as line-out mode and in-ear headphone mode, respectively, and adjusts the output automatically. Therefore, the output impedance comes out to be a huge value. The method of bypassing this solution varies from manufacturer to manufacturer. As the device evolves further, the standard loses its power. And this is going the right way.


I do not want to admit it, but the measurement by the consumer will lose power. Device will be equipped with various solutions and functions for each manufacturer in the future. This is especially true for smart amplifiers. Klippel and some of the company's patented "smart amplifiers" can detect various information including speaker distortion and voice coil displacement just by being connected to a speaker terminal. The measurement is valid and usable only when DUT is raw . Many devices in the past were raw, so measurements were useful. But not now. And also in the future. Features for the consumer will be added and they make the measurement impossible or unnecessary. But this should not be bad criticized.

The AHB2 is not a smart amplifier, but it is not a completely raw amplifier. As I said earlier, the AHB2 has protection for the consumer's ear or speakers. John siau says that it works in a way that does not affect sound quality. I agree with that. A typical consumer will be completely transparent when using this amplifier. However, it is not completely transparent when it measured by consumer. because they can not bypass protection. But you should not blame AHB2. This is because the protection mode is built for the consumer. Many devices will preclude standard measurements in the future.

There is no need to severe push past standards into the new era.

 

[RichB]

When I first connected the Benchmark LA4, the AHB2 was set to high-gain mode (top position) and the bypass setup left the volume loud in the + range. The sound was awful but I don't think the AHB2 clipping lights were on. It may be possible to overload the input gain.
This is not an experiment I wish to repeat.

Input gain should be set properly.
I suppose the level should be determined by which component has the best pre-amplification.

- Rich

 

[Sal1950]

The AHB2 is not a smart amplifier, b

But the designer is very smart.

There is no need to severe push past standards into the new era.

No need to throw out a great standard either IMO.
If you were around in the days when the FTC rulings were put into place you know what a revelation they were then. If some way of informing the consumer about the special circumstances involved when measuring amps such as this, fine. But I'd hate to go back to the days of "instantaneous power" ratings and all the craziness that's now going on in the multich video world. The FTC rule is a good one that might require just a bit of tweaking.

 

[RichB]

But the designer is very smart.


No need to throw out a great standard either IMO.
If you were around in the days when the FTC rulings were put into place you know what a revelation they were then. If some way of informing the consumer about the special circumstances involved when measuring amps such as this, fine. But I'd had to go back to the days of "instantaneous power" ratings and all the craziness that's now going on in the multich video world. The FTC rule is a good one that might require just a bit of tweaking.

My older bother had a Techniques receiver with .0001 (there may have been more zeros) that sounded awful driving his JBL L105s.
When he add the Phase Linear 300 WPC amp, it was a huge improvement. I assume that was Pre-FTC.

- Rich

 

[zalive]

Gain control is not an issue, except the input stage of AHB2 is obviously not smart (or adjusted to variety of input gains). But it's not least problem to adjust it manually. Like @Digital_Thor did as well:

I played on a small set of speakers, with a Maratnz PM-80 MKII SE wit ha few friends, while trying out different equipment. We then tried the AHB2 with an old high end Denon pre amp - cant remember the details of it. But the Benchmark started clipping easily, before we found out that you need to adjust the load on the rear. But still, there was no real improvement in sound. Maybe the Denon was not up to the job. But maybe, sometimes even good specs, does not equal better sound.

IMO any decent preamd should do its job - some may be bit better, some may be bit worse but you don't need any 'top 5' or hi end preamp to do the job a decent preamp is supposed to do.

If preamp or speakers should not disclose a difference between AHB2 and some other decent amp then one has to think for which system it should pay off to actually pay the money for this power amp. And I'm sorry to say this, but the answer is traditional: test it in your own system and your own room, prior to commiting to it. Otherwise prepare for possible scenario of disappointment (while the objectivist guys will try to explain to you what went wrong and why aren't you thrilled with the result).

Btw. the latter is the reason why I don't want AHB2. There's no 'no' but there's no 'yes' either in my view. I would like to try it prior to forming an opinion.

 

[SIY]

I've been working on a possible design myself. We should all collaborate on this. I know SIY wants one too.

I wish I could just borrow one long enough to open it up and see if it's passive or active. If I can figure out some basic coding (I'm remarkably software-challenged), I can set up an active load for 100 watts and under using the APx1701 sitting on my bench.

 

[svart-hvitt]

But the designer is very smart.


No need to throw out a great standard either IMO.
If you were around in the days when the FTC rulings were put into place you know what a revelation they were then. If some way of informing the consumer about the special circumstances involved when measuring amps such as this, fine. But I'd hate to go back to the days of "instantaneous power" ratings and all the craziness that's now going on in the multich video world. The FTC rule is a good one that might require just a bit of tweaking.

Bob Stuart is smart too.

 

[restorer-john]

This is because the protection mode is built for the consumer. Many devices will preclude standard measurements in the future. There is no need to severe push past standards into the new era.

When it comes to smartphones and the possible long term hearing damage/loss possible from extended high level headphone use, the manufacturers are protecting themselves, with likely pressure from governing bodies the world over about potential remedial costs to their various health-care systems. As the effects become clearer, smartphones may end up with taxes on them to cover future hits to the health system akin to cigarette taxes used in many countries.

We've had amplifiers in the past that used load impedance analysis of the connected load (eg Technics SEA-3mkII from the 1980s) to determine maximum output powers, so the types of adaptive output you refer to are not new or novel. We've had amplifiers that adapt their power supply rails either by ramping up or down or switching between taps to control maximum output. Many AVRs have physical rear-panel hard switches for 8/4 ohm speakers that select appropriate PT taps.

All those amplifiers can still be tested using the Amplifier Rule. Many attacks to weaken the Rule have been attempted, but thank goodness the FTC still has it, largely untouched. The Japanese have their JEITA (formerly JIS) and the Europeans had their DIN (what is it these days?) standards. In this country, nobody took European rated products seriously until they were tested to US FTC standards, as their ratings were, shall we say, 'optimistic'. The FTC rule is the gold standard, still to this day.

The AHB-2 is clearly not a monster powerhouse of an amplifier, but what it does do, is maintain its behaviour perfectly up until it shuts down. That is a valid design choice. But premature shutting down, and an inability to endure its own US standard power rating specs is a serious shortcoming.

 

[Sal1950]

Bob Stuart is smart too.

Yea, he really knows how to make a lot of money, all the while sticking a knife in the consumers back.

 

[restorer-john]

I can see why someone would say that if it was the 1970's, but measurement equipment has come a long ways and engineers do know what to measure.

Sure, test gear is leaps and bounds more easily accessible and in real terms cheaper, but do the 'engineers' really know what to measure? More so than the pioneers of the industry?

Or are they merely standing on the shoulders of giants, rarely acknowledging that 'their' work is derived (borrowed) from the past, perhaps tweaked a little (or not) and taking all the credit for it? I see little humility, virtually zero acknowledgment of past trail-blazers and more 'proprietary' patents applied for, and hidden behind meaningless acronyms.

Tell me, when did you see a full slew of tests for a power amplifier, anywhere, in any magazine or review? When did you last read a full circuit analysis by a reviewer describing the novel (or lack of) circuit elements? You'll have to go back to the 60s, 70s and early 80s for that.

 

[RichB]

Yea, he really knows how to make a lot of money, all the while sticking a knife in the consumers back.

He has really thinned out the snake population extracting all that oil.

- Rich

 

[Kal Rubinson]

But premature shutting down, and an inability to endure its own US standard power rating specs is a serious shortcoming.

On the test bench. I do not know of reports of problems in practical use.

 

[restorer-john]

I played on a small set of speakers, with a Maratnz PM-80 MKII SE wit ha few friends, while trying out different equipment. We then tried the AHB2 with an old high end Denon pre amp - cant remember the details of it. But the Benchmark started clipping easily, before we found out that you need to adjust the load on the rear. But still, there was no real improvement in sound. Maybe the Denon was not up to the job. But maybe, sometimes even good specs, does not equal better sound.

Certainly don't be quick to dismiss the PM-80. It was a great value high powered integrated from Marantz. I have a comprehensive review of it someplace (IIRC it was in Australian HiFi) and it exceeded it specifications significantly in all areas. It's stereo power output is in exactly the same league as the Benchmark. I recall it hit over 300W/ch (or close to it) into 2ohms.

The only downfall with the original PM-80 was the voltage stage driver IC. They are unavailable (easily) when they fail. The PM-80Mk2/SE used a much better power amplifier stage which was completely discrete with optical (optocoupler) based bias switching and rail switching for the Class- A.

In short, the Benchmark may have an order of distortion lower than the Marantz, but other than that, the PM-80mk2SE would certainly not have been embarrassed in any technical way.

But it was built in a different era. Through hole and point to point harnesses. Bowden linkages to remote switches. It's an integrated with tons of functionality. The Benchmark is two boards, sandwiched together in a compact, modern form factor. The Benchmark is a work of art inside, that's for sure.

 

[cbnbmore]

The AHB2 no doubt has the look of a well planned and executed design. With the use of high end parts it’s easy to see why they measure and sound as excellent as they do.