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Review and Measurements of Benchmark AHB2 Amp

dlaloum

Major Contributor
But still none close to specs of ahb2, I mean just like there are many cheap thx AAA headphone amps , why no cheap speaker amp with equal or better specs than ahb2 ?
If you look at the THX website - their AAA amp tech is marketed only to headphone amps...


And the specs don't tell the whole story - a number of reviewers have noted that the AHB2 is not the best for difficult speaker loads (2ohm or less)
Clearly it is a very well regarded high quality amp at a reasonable/competitive price.

And by achieving such exemplary test results in a number of areas, it has set a benchmark, that we hope, many others will feel obliged to follow!!

All of which is good.

But, which of these exemplary specs affect the sound? - at what level of distortion, and/or noise, does any further improvement become academic.... inaudible - Given that the signal to noise of the typical living environment is well below 90db (in most cases below 70db) - how much is to be gained by a 120db S/N amp? let alone one with 130db+

If you have to choose between an amp with S/N of 80db, but very high current capability, which drives your specific speakers with ease - and one with S/N of 130db, but which struggles and strains with your specific speakers.... the decision is easy!

Best not to get overly hung up on the specs - they are worthwhile to a degree - (and could be a deciding factor between two very similar performing amps) - we are still struggling to determine what metrics affect the sound in which way.
 

aj625

Senior Member
If you look at the THX website - their AAA amp tech is marketed only to headphone amps...


And the specs don't tell the whole story - a number of reviewers have noted that the AHB2 is not the best for difficult speaker loads (2ohm or less)
Clearly it is a very well regarded high quality amp at a reasonable/competitive price.

And by achieving such exemplary test results in a number of areas, it has set a benchmark, that we hope, many others will feel obliged to follow!!

All of which is good.

But, which of these exemplary specs affect the sound? - at what level of distortion, and/or noise, does any further improvement become academic.... inaudible - Given that the signal to noise of the typical living environment is well below 90db (in most cases below 70db) - how much is to be gained by a 120db S/N amp? let alone one with 130db+

If you have to choose between an amp with S/N of 80db, but very high current capability, which drives your specific speakers with ease - and one with S/N of 130db, but which struggles and strains with your specific speakers.... the decision is easy!

Best not to get overly hung up on the specs - they are worthwhile to a degree - (and could be a deciding factor between two very similar performing amps) - we are still struggling to determine what metrics affect the sound in which way.
it means you may not have heard ahb2.
 

solderdude

Grand Contributor
a number of reviewers have noted that the AHB2 is not the best for difficult speaker loads (2ohm or less)

Weird.. Amir measured it bridged at 4ohm load (500W continuous) so that would mean in normal usage 250W in 2ohm.
Sure.. its not a doubling
in power (185W 4ohm should be around 350W in 2ohm) and protection may kick in but how many speakers are 2ohm or lower below 200Hz ?
That's where most of the needed music power goes in to.
 

dlaloum

Major Contributor
Weird.. Amir measured it bridged at 4ohm load (500W continuous) so that would mean in normal usage 250W in 2ohm.
Sure.. its not a doubling
in power (185W 4ohm should be around 350W in 2ohm) and protection may kick in but how many speakers are 2ohm or lower below 200Hz ?
That's where most of the needed music power goes in to.
Other way around with my speakers ... 1.6ohm @ 20khz... reactive tweeter... lots of amps end up just not sounding at ease...
 

solderdude

Grand Contributor
That's pretty low. But one has to consider that using music the 20kHz component (when present) is much lower in level than the lower frequencies.
And I mean 20 to 30dB lower in amplitude.
So when bass levels are near clipping (assuming 4ohm) = 25V = 150W in power the 20kHz 'power' is 15W peaks at max.
15W in 1.6ohm = 3A where the bass draws 6A and current limit seems to be 11A.
Also those 20kHz peaks will be very short lived so aren't an issue.
Nah... this speaker doesn't appear to be a too difficult load. Assuming phase is not too crazy.
 

aj625

Senior Member
If you look at the THX website - their AAA amp tech is marketed only to headphone amps...


And the specs don't tell the whole story - a number of reviewers have noted that the AHB2 is not the best for difficult speaker loads (2ohm or less)
Clearly it is a very well regarded high quality amp at a reasonable/competitive price.

And by achieving such exemplary test results in a number of areas, it has set a benchmark, that we hope, many others will feel obliged to follow!!

All of which is good.

But, which of these exemplary specs affect the sound? - at what level of distortion, and/or noise, does any further improvement become academic.... inaudible - Given that the signal to noise of the typical living environment is well below 90db (in most cases below 70db) - how much is to be gained by a 120db S/N amp? let alone one with 130db+

If you have to choose between an amp with S/N of 80db, but very high current capability, which drives your specific speakers with ease - and one with S/N of 130db, but which struggles and strains with your specific speakers.... the decision is easy!

Best not to get overly hung up on the specs - they are worthwhile to a degree - (and could be a deciding factor between two very similar performing amps) - we are still struggling to determine what metrics affect the sound in which way.

Out of interest, have you heard it? If so, some feedback on subjective SQ would be appreciated.
I owned it long before it was even measured here.
 

Donovan

Member
Any word on Benchmark releasing a 3 and/or 5 channel amp? Since they are backlogged currently on their 2-channel flagship model, I suppose they don’t need any additional business.
 

Kal Rubinson

Master Contributor
Industry Insider
Forum Donor
Any word on Benchmark releasing a 3 and/or 5 channel amp? Since they are backlogged currently on their 2-channel flagship model, I suppose they don’t need any additional business.
No word that I've heard. OTOH, I really doubt it is in the works since (1) the mch market is much smaller than the stereo market and (2) the AHB2s are so compact. I have 3 of them and, stacked together, they are still smaller and lighter than most traditional stereo power amps.
 

aj625

Senior Member
Out of interest, have you heard it? If so, some feedback on subjective SQ would be appreciated.
It's what you feed it. I have tried it with very cheap sources like mobile phone to very high end dac cum pre. With high quality source it sounds lot more open, dynamic without being bright. It is like a window. It does not add anything of its own. If someone is looking for extra preference for certain frequencies like bass or vocals or rolled off treble, it won't provide it. So imo try to feed it with ultra clean signal of a well measured dac and it will reward you with unbelievable realism.
 
It's what you feed it. I have tried it with very cheap sources like mobile phone to very high end dac cum pre. With high quality source it sounds lot more open, dynamic without being bright. It is like a window. It does not add anything of its own. If someone is looking for extra preference for certain frequencies like bass or vocals or rolled off treble, it won't provide it. So imo try to feed it with ultra clean signal of a well measured dac and it will reward you with unbelievable realism.
Thanks for the impressions.

I've owned several amps over the years capable of differentiating between different quality sources, and seemingly pretty neutral in terms of balance. I'd be interested to hear an AHB2 to see if it brings anything new to the table subjectively that the others haven't. Will try to get a home demo as soon as it's possible.
 

aj625

Senior Member
Thanks for the impressions.

I've owned several amps over the years capable of differentiating between different quality sources, and seemingly pretty neutral in terms of balance. I'd be interested to hear an AHB2 to see if it brings anything new to the table subjectively that the others haven't. Will try to get a home demo as soon as it's possible.
What i have found over the years that more transparent your system becomes more it is transparent to faults of your power and cable chain. Ie any power emi, rfi noise percolating through power or cables will also be easily evident. So it better to plug those routes of noise. I use few ifi ac purifier in reverse polarity ( it somehow works better in reverse polarity for me ) ferrited power cable, usb cable. I use ferrite everywhere except on analog interconnects. So I am able to suck pretty much last bit of noise from the chain. It has resulted in extremely black background. Instruments don't have any kind of outline and seem to come out suddenly and independently. No information is left behind but everything is still so sweet and smooth.
 
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dlaloum

Major Contributor
I have a collection of different size ferrites that I use on various cables... it's no panacea - but it can help
 

anmpr1

Major Contributor
Forum Donor
What i have found over the years that more transparent your system becomes more it is transparent to faults of your power and cable chain... No information is left behind...
What exactly is 'transparency' in a hi-fi? I am seriously asking. What exactly is it?

In conjunction with that question, can you cite exactly what the 'information that is left behind' consists of? And how do you suppose it is being 'left behind'? That is, the mechanism responsible for deleting information. Does the missing information consist of missing frequencies, possibly an abnormal variance in FR, or does it consist of added noise/distortion, that is audible? A combination of all those, together?

If it is FR/noise/distortion related, and if it is audible, do you think it could be measurable? If you think that it is amenable to measures, do you know of anyone that has measured it, or attempted to? Can you point out any studies that have reliably measured this 'transparency' factor, that consists of varying degrees of 'missing information'?

Finally, can you explain, exactly, the 'faults' in your AC electrical power? What these faults are, and how this affects the DC in your gear's circuits, after rectification? And, do you think these faults can be measured, as above?
 

aj625

Senior Member
What exactly is 'transparency' in a hi-fi? I am seriously asking. What exactly is it?

In conjunction with that question, can you cite exactly what the 'information that is left behind' consists of? And how do you suppose it is being 'left behind'? That is, the mechanism responsible for deleting information. Does the missing information consist of missing frequencies, possibly an abnormal variance in FR, or does it consist of added noise/distortion, that is audible? A combination of all those, together?

If it is FR/noise/distortion related, and if it is audible, do you think it could be measurable? If you think that it is amenable to measures, do you know of anyone that has measured it, or attempted to? Can you point out any studies that have reliably measured this 'transparency' factor, that consists of varying degrees of 'missing information'?

Finally, can you explain, exactly, the 'faults' in your AC electrical power? What these faults are, and how this affects the DC in your gear's circuits, after rectification? And, do you think these faults can be measured, as above?
Transparency is high fidelity. High fidelity means closer to original performance. Details are lost due to distortion and noise. Try ahb2 directly fed by a good measuring dac like d90se or tt2 directly while ahb2 in low gain or rather drive efficient speakers directly out of dacs like tt2. Over the years hi fi is moulded into what is overly colored by distortion or faulty fr. You can't avoid color during recording but you can always minimise it by less processing. Similarly you can minimise color during playback too.
 

rdenney

Major Contributor
Forum Donor
Transparency is high fidelity. High fidelity means closer to original performance. Details are lost due to distortion and noise. Try ahb2 directly fed by a good measuring dac like d90se or tt2 directly while ahb2 in low gain or rather drive efficient speakers directly out of dacs like tt2. Over the years hi fi is moulded into what is overly colored by distortion or faulty fr. You can't avoid color during recording but you can always minimise it by less processing. Similarly you can minimise color during playback too.
I would modify that--high fidelity playback isn't trying to be closer to the performance--that's the microphone and recordist's job. It's trying to be closer to the input signal, whatever that is. And the processing the recordist does may be an effect that is part of the creative process. Or it may be a manipulation demanded by A&R people who think the effect will make it sell better. Or some combination of the two. The processing may be corrective--to overcome defects in the microphone setup. There are a zillion possibilities, with only a half-zillion being negative (and just try getting audiophiles to agree on which half-zillion represents evil).

Of course, sometimes the input signal sucks and people want the playback system to make it sound good. But building that correction into the system without the option makes those recordings that didn't need it sound worse. But that's okay, because audiophiles will then declare those recordings as being poor and won't play them.

As to low gain versus high gain on an AHB-2, it depends on the performance of the input at a given voltage. Some DACs can put out 10 volts, but will they perform as well with 10 V RMS output as the intermediate gain stage in the Benchmark? The answer to that is not obvious to me.

Rick "the amplification has to be done somewhere" Denney
 

aj625

Senior Member
I would modify that--high fidelity playback isn't trying to be closer to the performance--that's the microphone and recordist's job. It's trying to be closer to the input signal, whatever that is. And the processing the recordist does may be an effect that is part of the creative process. Or it may be a manipulation demanded by A&R people who think the effect will make it sell better. Or some combination of the two. The processing may be corrective--to overcome defects in the microphone setup. There are a zillion possibilities, with only a half-zillion being negative (and just try getting audiophiles to agree on which half-zillion represents evil).

Of course, sometimes the input signal sucks and people want the playback system to make it sound good. But building that correction into the system without the option makes those recordings that didn't need it sound worse. But that's okay, because audiophiles will then declare those recordings as being poor and won't play them.

As to low gain versus high gain on an AHB-2, it depends on the performance of the input at a given voltage. Some DACs can put out 10 volts, but will they perform as well with 10 V RMS output as the intermediate gain stage in the Benchmark? The answer to that is not obvious to me.

Rick "the amplification has to be done somewhere" Denney
Tt2 can output 6v out of XLR at -3L with low gain of ahb2 it becomes around 18v. With 8ohm speakers it becomes around 40w.
 

anmpr1

Major Contributor
Forum Donor
Details are lost due to distortion and noise.
Thanks for clarifying. When you were talking about 'faults' in your cable and power chain, and 'information left behind', I wasn't sure but that you were talking about something other than FR, distortion and noise. I agree with those parameters. And certainly ground loop hum can impose difficulties that need addressing.
 
I would modify that--high fidelity playback isn't trying to be closer to the performance--that's the microphone and recordist's job. It's trying to be closer to the input signal, whatever that is. And the processing the recordist does may be an effect that is part of the creative process. Or it may be a manipulation demanded by A&R people who think the effect will make it sell better. Or some combination of the two. The processing may be corrective--to overcome defects in the microphone setup. There are a zillion possibilities, with only a half-zillion being negative (and just try getting audiophiles to agree on which half-zillion represents evil).

Of course, sometimes the input signal sucks and people want the playback system to make it sound good. But building that correction into the system without the option makes those recordings that didn't need it sound worse. But that's okay, because audiophiles will then declare those recordings as being poor and won't play them.
I've been forced to play with various levels of fidelity over the years as I find a reasonable amount of the music I love isn't necessarily recorded well enough to enjoy on a some super-revealing systems, but refuse to let my system dictate what I can listen to. My main rig is very good at walking this fine line between the information being there and no obvious spectral imbalances, but being 'forgiving' (for want of a better description) of less than stellar recordings that I can still really enjoy them. That's a 5.1 system with active DSP speakers and a sub, etc., though, so the amplification is built-in. I'm trying to get a similar kind of sound quality for my passive speaker system in a second room, so hence the need for an amp which walks the same line... Closest I've ever heard was a McIntosh - everything there which I know is on a recording but 'forgiving' enough to sit back and just enjoy the music. But McIntosh are eye wateringly priced in the U.K.

I don't know how 'transparency' is gauged in subjective terms, simply because unless the listener was present at the recording, I'm not sure what they're using as a baseline for that claim. With all the half-decent amps, speakers and sources I've had over the years, once you've heard a detail in one listening session, on one piece of equipment, you can then go and hear it on the others too, so it seems the information is basically there for the most part. In fact, I'm more wary when a piece of equipment/system sounds dramatically different to the norm. The most extreme example of this I personally experienced occurred around 20 years ago, when I was a young guy and when to demo some Naim gear. The dealer paired the CD player with a low-end (by Naim standards) amp and some speaker or other that was en-vogue with Naim gear at the time. Well I took along a few CDs and opened with Buena Vista Social Club, which was also one of the recordings everyone used in the day. About 4 bars into El Cuarto de Tula there's a deep drum which is struck at the beginning of each phrase. Every system upon which I've ever heard that recording, to this day, presents the drum as a fairly softly struck "boooom" sound. On that Naim system, that day, it went BLAM! right through the seat of your pants. It was electric. I'm almost sure it's wildly inaccurate - in comparison to equipment I believe to be pretty balanced, I think the Naim system was actually bass-light and quite 'edgy' which subjectively made it sound very fast and rhythmic. I think I'd have had severe listening fatigue within a few hours of owning it (I bought something else in the end) but to this day I miss it every time I listen to that track and am always disappointed even though I know it likely wasn't recorded that way. Who knows, though, since I wasn't there at the session - maybe the Naim was right and every other piece of equipment I've listened on is wrong.

Ideally, it would be nice to have a system revealing enough for the very good recordings, which would be sublime on it, but be able to store custom EQ for those which aren't. This isn't as easy as you'd think though - a lot of the time, a global frequency tilt won't do it, and neither will general bass/treble cut or boost, you have to try and find specific frequencies to cut/boost - a bit beyond the pale for home use. Other times, most of a recording is well balanced, but they recorded the strings too hot, or the hi-hat, whatever... ultimately I'm not in the studio and just want to listen and not bugger around too much... Another alternative would be to try for a general EQ of a more 'forgiving' system. This, I suppose, might be possible, but I'm not sure it would be completely easy - things such as damping factor, certain THD/IMD at given frequencies, and very slight rounding of square wave response, etc., etc., might not be that obvious to EQ in...?

[Edit: to be fair to the Naim electronics, I believe the speakers also had a decent part to play in this particular sound - can't remember what they were for the life of me, unfortunately!]
 
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