Review and Measurements of Benchmark AHB2 Amp

[SIY]

That should be fine unless the Oppo is unusually noisy. Otherwise, break out the soldering iron and connect pins 2 and 3 of an XLR plug together.

 

[peng]

What is the recommended method for shorting an XLR input connection?
Is this necessary, If I connect the input to the Oppo UPD-205 (powered on) and muted?

- Rich

If that does not work (it may be muted/isolated via a relay), try turning the analog output and turn its volume to minimum. Regardless, that 170 mV, if it is a steady reading, my best guess is that it is ultrasonic noise (as mentioned before) leaked through from the switching power supply. If it is not ultrasonic then you should be hearing something, hum, hiss etc.. So if you put your ears near the speakers and don't hear anything then it may be just normal, by design. Have you tried contacting ATI tech support yet?

 

[spaace]

Here is something i found when i was digging up more data on the abh2 ....can someone comment whether it is a technically sound statement ?

"SMPS in the AHB2 is regulated (deliberately limited) such that the amplifier stays within its sweat zone for distortion. Whilst maintaining the good distortion numbers this does affect its headroom (dynamics), it doesn't allow instantaneous volume peaks that exceed the predetermined limits. This is unlike, say, a "normal" linear power supplied Class AB amplifier. They do allow for much higher volume peaks than their continuous power rating would indicate, and sacrifice a small amount of distortion as a result. Most consider this a non issue due to the overall loudness and the fact that the duration is so short that any additional distortion is inaudible."

 

[zalive]

Policy of Benchmark is obviously a good benchmark (measurements). Limited dynamic headroom won't add distortion, while it will impact the quality nevertheless - it's just distortion numbers won't reveal it.

It might be a personal angle on what the better quality is (lower distortion before dynamic headroom), or it might be a marketing approach where lower measured distortion numbers promote sales to objectivists. Or it might be both. Take your pick. On some things you just can't escape having beliefs simply because you'll never know the truth behind

They do allow for much higher volume peaks than their continuous power rating would indicate, and sacrifice a small amount of distortion as a result. Most consider this a non issue due to the overall loudness and the fact that the duration is so short that any additional distortion is inaudible."

Or you can have it all, both low distortion numbers and dynamic headroom, when using a power section of a proper headroom. This comes with a price, of course.

 

[wynpalmer]

Policy of Benchmark is obviously a good benchmark (measurements). Limited dynamic headroom won't add distortion, while it will impact the quality nevertheless - it's just distortion numbers won't reveal it.

It might be a personal angle on what the better quality is (lower distortion before dynamic headroom), or it might be a marketing approach where lower measured distortion numbers promote sales to objectivists. Or it might be both. Take your pick. On some things you just can't escape having beliefs simply because you'll never know the truth behind



Or you can have it all, both low distortion numbers and dynamic headroom, when using a power section of a proper headroom. This comes with a price, of course.

I own an AHB2 coupled with a pair of electrostatics that are rated at 200W with a specified load resistance of 4 ohms, even though the actual impedance varies from a few kohms at LF to 0.9 ohms at about 30kHz. I've previously used the speakers with a variety of amps, including some class AB ones, most of which boast that they have pretty stiff, if not regulated, supplies with low dynamic droop, so I'm not sure where the extra headroom comment comes from.
In general I've been careful not to expose the speakers to excessively powerful sources for fear of damage, so my other normal amp is a Rogue M180 which supposedly delivers 180W into 4 ohms and which had an upgrade from Rogue to increase the storage capacitance for the supplies in order to "stiffen" them and improve the "sound".
This suggests that the practice of having non-stiff supplies is not a usual one for Hifi amps. Perhaps in the professional arena, where the AHB2 was designed to play, having stiff supplies is less common and what matters is the dynamic power available.

 

[RichB]

Policy of Benchmark is obviously a good benchmark (measurements). Limited dynamic headroom won't add distortion, while it will impact the quality nevertheless - it's just distortion numbers won't reveal it.

It might be a personal angle on what the better quality is (lower distortion before dynamic headroom), or it might be a marketing approach where lower measured distortion numbers promote sales to objectivists. Or it might be both. Take your pick. On some things you just can't escape having beliefs simply because you'll never know the truth behind

Or you can have it all, both low distortion numbers and dynamic headroom, when using a power section of a proper headroom. This comes with a price, of course.

Prior to the AHB2's, I had ATI AT6000's which were massive. The power difference between them and the ATI AT4000 series was 200 versus 300 WPC, or 1 dB. These are not regulated so they have about 1.5 dB of headroom. I don't know if the AHB2 has dynamic power, I suspect it does while not voltage clipping. The power-cube measurements posted earlier in this thread are an indicator.

The AHB2 bridged is going to provide similar power to the ATI's.
If you are listening on the edge of clipping any of these amps, you probably need 2kwatts to be safe

In my system, the trade off is obviously tilted to lower distortion since I am not clipping music or movies.
Clipping indicators per channel are a wonderful feature.

- Rich

 

[RichB]

I have no experience with the 115 but the 87 V is excellent. A little pricey at over C$500, but it will definitely do a good job for you on audio stuff.
170 mV is crazy high if there is no inputs even connected. The 115 can measure frequency so I would suggest you do it and see what it shows. Switching frequencies are way too high for such multi-meters but that could be the reason for the crazy reading.

The Fluke 87V is providing much better results.
The AHB2, AT522NC, and leads together all measure approximately 0.4 mV, essentially nothing.
The Fluke 115 may have been confused by AT522NC high-frequency noise.

The 115 could not measure frequencies above 1kHz.

The 87V was frequency measurements are interesting.
With the AHB2, it had no problem measuring the sine-wave FLAC files tested: 50, 250, 400, 1k, and 2k Hz.
With the AT522NC, it could not measure any frequency without the low pass filter engaged.
Without the low-pass filter, all the above sine-wave files measurements were bouncing around 1kHz.

The 87V measured the AT522NC idle high-frequency noise at 425kHz, which must be from the NCore modules since the power supply is linear (non switching). The AHB2 measurement was zero mV, no noise.

- Rich

 

[Digital_Thor]

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:



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.

Thank you. My intention was never to say that the AHB2 was bad or anything like that. I just did not find much difference - in practical listening subjective terms.
I also had the opportunity to try and swap between a Behringer EP4000 and a set of Dan D'Agostino mono blocks on a set of Magico Q7. Cant remember the pre or the DAC - but they were very expensive too. The mono's did sound a little nicer than the EP4000 - which I kind of hoped too, since the price difference is - big. But I think I could live with the Behringer, when I think of the importance of the speakers in comparison with the importance of the amplifier - also with some serious consideration towards my financial situation.
Again - the mono's played really good. But since few of us have the possibility to pay up so easily, then compromises has to be made.
I know I should have read the manual. But the guy who brought it to our little gathering, forgot too.
The Marantz played nicely and I always enjoyed it and did not even think of looking at the specs. I used to think of specs all the time, but maybe I just grew older and started to ask the question - "Does it work - for me?".
The science of technology is one thing. But trying to make science of human experiences and perception - that's one hell of a big subject too.

 

[maty]

Thank you. My intention was never to say that the AHB2 was bad or anything like that. I just did not find much difference - in practical listening subjective terms.
I also had the opportunity to try and swap between a Behringer EP4000 and a set of Dan D'Agostino mono blocks on a set of Magico Q7. Cant remember the pre or the DAC - but they were very expensive too. The mono's did sound a little nicer than the EP4000 - which I kind of hoped too, since the price difference is - big. But I think I could live with the Behringer, when I think of the importance of the speakers in comparison with the importance of the amplifier - also with some serious consideration towards my financial situation.
Again - the mono's played really good. But since few of us have the possibility to pay up so easily, then compromises has to be made...

Another very limiting factor is the quality of the reproduced recordings. As I write many times, with the current commercial music, so badly recorded, it is not necessary to spend a lot of money on the equipment.

What kind of music did it sound during the test? Jazz, classical... or electronic with synthesized instruments, voices after Autotunes.

Although the equipment was expensive or very expensive, any existing bottleneck in the chain can act as a very limiting factor. Almost always they are not easy to discover.

 

[Sal1950]

Thank you. My intention was never to say that the AHB2 was bad or anything like that. I just did not find much difference - in practical listening subjective terms.

And that is to be as expected. I don't think anyone here has claimed magical sound qualities to the AHB2. IMO if listened to in a bias controled DBT against any number of properly designed amps from the last few decades, you would be hard pressed to hear any difference.
It is a amazing design that has brought together relatively high power with low heat creation and AC power usage. Then added some of the best measurements that have ever been attained in a power amplifier. If your in the market for a new amp and $3k is in your ballpark, you can purchase it secure in the knowledge you now own the very top of the line in modern amp design.
But your absolutely correct that if you have to chose between a $3k amp with a $300 speaker, and a $300 used well designed amp with a $3k speaker, there shouldn't be a moments debate. Spend the big money on a speaker.

 

[anmpr1]

Another very limiting factor is the quality of the reproduced recordings. As I write many times, with the current commercial music, so badly recorded, it is not necessary to spend a lot of money on the equipment.

Generally, the better the system, the easier it is to tell poorly recorded sources. I never worried about it, or even noticed how things were recorded, when my source was a fold out suitcase style record player, with detachable speaker. The worst record ever made was the Murray Hill release of Furtwangler's 1950 La Scala Ring. The upside was that you got 40 minutes of horrible sound per LP side. So the portions were large.

 

[Sal1950]

Generally, the better the system, the easier it is to tell poorly recorded sources. I never worried about it, or even noticed how things were recorded, when my source was a fold out suitcase style record player, with detachable speaker.

That's the double edged sword of becoming a audiophile, the better your system gets, the worse a very large number of your favorite music sounds.

 

[Blumlein 88]

Generally, the better the system, the easier it is to tell poorly recorded sources. I never worried about it, or even noticed how things were recorded, when my source was a fold out suitcase style record player, with detachable speaker. The worst record ever made was the Murray Hill release of Furtwangler's 1950 La Scala Ring. The upside was that you got 40 minutes of horrible sound per LP side. So the portions were large.

Yes true. But what also happened once I had a fairly good listening setup is it allowed me to enjoy some types of music that were of no interest over the low quality system.

 

[Digital_Thor]

Yes true. But what also happened once I had a fairly good listening setup is it allowed me to enjoy some types of music that were of no interest over the low quality system.

Indeed.
When I build my own speakers I also went for multi subs. And that was a big benefit for all types of music. Of course I can hear tons of small problems in the higher notes and the bass is still worse, when the recording/mixing is bad - no matter how well I tuned my subs to blend evenly.
But on the other hand. There is so much music in the world - that I can simply skip the worst recordings and move on.

 

[RichB]

And that is to be as expected. I don't think anyone here has claimed magical sound qualities to the AHB2. IMO if listened to in a bias controled DBT against any number of properly designed amps from the last few decades, you would be hard pressed to hear any difference.
It is a amazing design that has brought together relatively high power with low heat creation and AC power usage. Then added some of the best measurements that have ever been attained in a power amplifier. If your in the market for a new amp and $3k is in your ballpark, you can purchase it secure in the knowledge you now own the very top of the line in modern amp design.
But your absolutely correct that if you have to chose between a $3k amp with a $300 speaker, and a $300 used well designed amp with a $3k speaker, there shouldn't be a moments debate. Spend the big money on a speaker.

I don't find it unreasonable to make comparisons in your home, but at a minimum, such comparisons should be volume match them by measuring the voltage at the speakers.

I have done this with the AHB2 and AT522NC and after countless hours of listening, I have developed a firm opinion that these amps are distinguishable when level matched when driven directly by the Oppo UPD-205 XLR outs.

Voltage Target 1.45.
Oppo volume 39, AHB2 measures 1.42 Volts
Oppo volume 28, 522NC measures 1.435 Volts

Voltage Target 2.83 (Approximately 1 watt)
Oppo volume 51, AHB2 measures 2.83 Volts
Oppo volume 40, AT522NC measures 2.85 Volts

Amplifier measurements are not consistently applied and, even when applied within a review site, may not represented worst case example of both linear (amplitude) and non-linear distortions. Distortion tests are looking for distortion not related to the signal and not necessarily to power sags, phase shift that can affect the performance driving a loud speaker.

The AHB2 is one of the most measured amplifiers out there with different methodologies and time and again, displays exceptional performance. Perhaps, that has led to confirmation bias but before any of that, I heard them and found something new...

I don't know if we will ever have the desired DBT, but my expectation, is that they would indeed show a difference with the right system, room, listeners, source, etc,..

- Rich

 

[RichB]

That's the double edged sword of becoming a audiophile, the better your system gets, the worse a very large number of your favorite music sounds.

I listen to a lot of popular music and find that improvements to my system make even over produced and compressed music sound better. When CD players first appeared with HDMI outputs, I used them because digital was perfect and better. I had an Auzentech sound card which really sounded good/better but I assumed there was some processing that must be equalizing or otherwise altering it and dismissed it.

It wasn't until Oppo offered to send me a BDP-105 (I was a beta tester) that I tried the analog outputs and recordings that I thought were middling sounded better.

HDMI has improved since then but with each improvement to my system, I have not found suddenly unlistenable content. Actually, the opposite is true. Usually, the instruments are better defined and the recording is more enjoyable.

To be fair, there are recording that sound better in my car

- Rich

 

[D700]

That's the double edged sword of becoming a audiophile, the better your system gets, the worse a very large number of your favorite music sounds.

I've been using a Scotch filter for years to handle that sort of thing. It seems to work best if I level match the vintage with album release date.

 

[zalive]

That's the double edged sword of becoming a audiophile, the better your system gets, the worse a very large number of your favorite music sounds.

When this happens you need that reset button to forget everything you 'know' since things obviously took the wrong path. With absolutely better system usually all the recordings sound better than with the worse system. There will be inevitable difference with recordings quality of course, but systems 'punishing' for bad recordings are IMO flawed - they need good recordings to mask their flaws which otherwise become apparent.

 

[Soniclife]

I've been using a Scotch filter for years to handle that sort of thing. It seems to work best if I level match the vintage with album release date.

Good plan. The Armagnac adjustment also works well, just retesting this to make sure it still works, yep, system sounds magic now.

 

[Sal1950]

There will be inevitable difference with recordings quality of course, but systems 'punishing' for bad recordings are IMO flawed - they need good recordings to mask their flaws which otherwise become apparent.

Please, most 50-60 rock and blues recordings have just about everything done badly that can be done badly..

To be fair, there are recording that sound better in my car

More so when that music was new and I was playing them on the tube radio in my 56 Chevy. So smooth sounding even with the vibrator softly buzzing in the background.