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Review and Measurements of Benchmark AHB2 Amp

cjm2077

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I have read (here on ASR) how the goal (or at least some listener's goal) is to have a sound system that let's them 'hear' what the recording engineer heard. If that is the goal (it's not my goal, but it could be someone's) then they had better find out what loudspeakers were used on mixdown, where they were positioned, and the loudness level used. But I really think what they are saying is that they want a loudspeaker that is 'neutral', i.e., reasonably flat across the board, and exhibits fairly low distortion.

The argument about the goal of hi-fi being to accurately reproduce the sound of acoustic (unamplified) instruments in a given space more or less took off with Harry Pearson. His 'absolute sound', as it were. The irony is that Pearson used some of the most colored and frankly downright weird audio gear for his reference. But if you told Harry that he'd just call you a rude name.

I'd say I'm in that first camp, trying to get as close to what the engineer heard or intended, but of course realizing the limitations inherent in that. So I try to get everything as neutral as possible, from the electronics to the speakers to the room. And hope that the engineer aimed for the same target as well, knowing that sometimes they probably don't. Some studio monitors are notoriously non-neutral, but engineers who use them usually know that and are using them to check certain features of the mix on them. I also know I'm not playing the music back at studio standard level all the time (which probably varies from engineer to engineer, but also isn't incredibly loud because they have to work at the same volume all day every day), but you live with the volume your environment can handle at the moment. I've got some room treatment, but it is a general living room, so you can only really do so much, and I'm ok with that. I think I'm well into the diminishing returns region of the curve for just about everything in my system, so I'm more than happy with it. The AHB2 performs much better than I actually need, but it's also an interesting state of the art piece of equipment for a not completely irrational price, and I could afford it, so why not?
 

jaynewt

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where the previous amps broken? There should be no audible diffrence!
Subjective indeed but all I can say is that I can hear more than with other amplification, especially the sound of reverb dying away to nothing and more fine detail on cymbals, etc. I'm pleased, especially as the ABH2 cost a fraction of the Kalugas.
 

cjm2077

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Subjective indeed but all I can say is that I can hear more than with other amplification, especially the sound of reverb dying away to nothing and more fine detail on cymbals, etc. I'm pleased, especially as the ABH2 cost a fraction of the Kalugas.

I was going to say, you must have spent mucho moolah on all that Mola.
 

Coach_Kaarlo

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I have been working on trying to make sense of my subjective observations re the audible and visible discrepancy in AHB2's dynamic performance compared with other amps. Lots of great discussion on here, and interesting insights which have helped me get further with my understanding - and maybe closer to solving the problem. Thanks to all for the contributions - and patience with my sometimes painfully obvious gaps in knowledge.

It's an existential problem this hifi one - sounds good versus is good. I think measurements are a valuable starting point to compare, analyse, understand - but ultimately we listen to music through our ears at home in rooms of questionable acoustical quality. If you measure a difference but are unable to hear a difference it only matters in a subjective way. In other words if you cannot taste the difference between a 25 year old single malt and a blended 25 dollar scotch whiskey - drink and enjoy the 25 dollar one!! Unless your ego or pride dictate otherwise of course. Understanding seems the ideal result of hearing (experiencing) a difference and using measurements to observe the same difference (proving).


A day ago when picking up my 'new' Yamaha NS-2000 speakers I was able to spend some time comparing the rare Harman Kardon Citation XX amplifier with the Benchmark AHB2 x 2 (running in mono) and AHB2 x 1 (running in stereo). The Accuphase P300 from my previous posts was sold unfortunately so not possible to test again.

http://www.thevintageknob.org/harman_kardon-Citation_XX.html

The AHB2 is ground breaking, and this Harman Kardon is another ground breaking amp from a time when product design intent was more closely related to excellence in performance and less to budget and marketing (and warranty) IMO. Meaning that some of these old amps still out-perform many many modern amps designed with modern tools and components. Speakers for example - the Yamaha NS-2000 speakers measure roughly 10-15% less overall than the latest NS-5000 speakers despite almost 40 years separating them and $2.5k v $20k in price respectively.

So while I can somewhat agree to arguments about technological and material advances which have been achieved during the last 40 years, when it comes to open mindedly measuring and listening to different equipment and comparing - much modern equipment is not worth a fraction of the price paid/ asked.

The listening and measuring of the AHB2's with the NS-2000 speakers was very satisfying, the speakers have a reputation for revealing flaws in the audio chain due to their accuracy,clarity, and transparency. Despite the fact they are becoming harder to find, I think the effort was worth it because they seem to be a good match for the AHB2 due to it's exceptional abilities to keep the signal path clean and pure from source to speaker. The speakers have been well voiced to my ears, instruments and vocals are extremely realistic and accurate. Sound stage is out to almost 180 degrees horizontally - over the shoulders in other words. And they measure flat with a little mid range warmth. In summary, so far, my thinking has been supported by my measuring and listening - even a 40 year old pair of speakers can sound great with decent amplification.



One thorn continues to dig into my subjective well being (aka happiness) score however. The base response. Specifically the dynamic attack, or instantaneous peaks, leading edge. Unfortunately I did not take the laptop or microphone to the pick-up as I was merely intending to grab my speakers not spend 6 hours comparing amps. So what follows are subjective observations from a scientific/ engineering POV.

I focused on small sections of tracks, 10 seconds max, set levels of that portion of the track with an SPL meter. Play adjust play adjust then finally get levels the same then loop that portion of the track repeatedly until the brain and ears can identify the differences or lack of same. Many many different types of music but all with a consistent observable difference in the kick drum.

When you look at an audio spectrograph which has deep bass and kick drums, the kick drum frequency extends the total SPL above the continuous bass SPL. The kick drum attack is on top of the bass. It was absent from the AHB2 no matter how I tried different tracks and SPL combinations - turning up the power did not help, although running in mono was much much better (making me think power or current are part of the issue) . A kick drum has a fundamental around 40-100Hz but has mids and highs from 300-1200Hz. The AHB2 could not reproduce the leading edge 'kick' that other amps could. Different speakers, different amps - all managed to deliver some kind of leading edge punch. Even a small studio monitor running off each amp showed a clear difference despite the ease of driving the little speakers (therefore eliminating the amp power etc). Physical cone extension (mentioned in my original post) was much better with AHB2 x 2 in mono, no difference observable between the amps.

When I looked at the impedance curve of the NS-2000 it's dropping from +90 ohms @ 40Hz to 8 ohms @ 100Hz on the woofer. It seems like the speaker is being a little difficult to drive in that area, and the current demand of moving the cone might be beyond the amp. Meaning big magnet, big cone, dropping impedance requiring some decent headroom to deliver an accurate reproduction of the audio signal. As always a pair of headphones can clearly demonstrate what I am talking about compared with a live amp - particularly because it runs though the DAC/ preamp so therefore isolates the amp.



So help me understand and prove my observations. How can I best measure this phenomena? I am thinking REW, microphone 1000mm away from speaker centered on the woofer driver, and then overlay the amplified measurement with original digital audio sample to compare.

And I can also do the test with stereo AHB2 and 2 x mono AHB2's - because the latter is hands down better in this respect despite never clipping in either setup.

As always replicate the test before you comment because if a clueless novice like me can hear and experience the difference someone with professional experience and years of knowledge will probably experience things that I am unaware of...... which may be able to explain what I am experiencing.

Cheers.

P.S. - there are ongoing negotiations re acceptable room treatments - the succulents proved to be both reasonable diffusers and partner permitted additions. Just need to find something thicker on the floor in front of the speakers and something MUCH thicker bushier in the corners for bass traps.

P1055369.JPG
 

Pjetrof

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Nice speakers! Concerning the amps, I m not an EE but at 52 tried any amp etc etc, if amp is not clipping, broken and well made there should be no audible diffrence!
 

RichB

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I have been working on trying to make sense of my subjective observations re the audible and visible discrepancy in AHB2's dynamic performance compared with other amps. Lots of great discussion on here, and interesting insights which have helped me get further with my understanding - and maybe closer to solving the problem. Thanks to all for the contributions - and patience with my sometimes painfully obvious gaps in knowledge.

It's an existential problem this hifi one - sounds good versus is good. I think measurements are a valuable starting point to compare, analyse, understand - but ultimately we listen to music through our ears at home in rooms of questionable acoustical quality. If you measure a difference but are unable to hear a difference it only matters in a subjective way. In other words if you cannot taste the difference between a 25 year old single malt and a blended 25 dollar scotch whiskey - drink and enjoy the 25 dollar one!! Unless your ego or pride dictate otherwise of course. Understanding seems the ideal result of hearing (experiencing) a difference and using measurements to observe the same difference (proving).


A day ago when picking up my 'new' Yamaha NS-2000 speakers I was able to spend some time comparing the rare Harman Kardon Citation XX amplifier with the Benchmark AHB2 x 2 (running in mono) and AHB2 x 1 (running in stereo). The Accuphase P300 from my previous posts was sold unfortunately so not possible to test again.

http://www.thevintageknob.org/harman_kardon-Citation_XX.html

The AHB2 is ground breaking, and this Harman Kardon is another ground breaking amp from a time when product design intent was more closely related to excellence in performance and less to budget and marketing (and warranty) IMO. Meaning that some of these old amps still out-perform many many modern amps designed with modern tools and components. Speakers for example - the Yamaha NS-2000 speakers measure roughly 10-15% less overall than the latest NS-5000 speakers despite almost 40 years separating them and $2.5k v $20k in price respectively.

So while I can somewhat agree to arguments about technological and material advances which have been achieved during the last 40 years, when it comes to open mindedly measuring and listening to different equipment and comparing - much modern equipment is not worth a fraction of the price paid/ asked.

The listening and measuring of the AHB2's with the NS-2000 speakers was very satisfying, the speakers have a reputation for revealing flaws in the audio chain due to their accuracy,clarity, and transparency. Despite the fact they are becoming harder to find, I think the effort was worth it because they seem to be a good match for the AHB2 due to it's exceptional abilities to keep the signal path clean and pure from source to speaker. The speakers have been well voiced to my ears, instruments and vocals are extremely realistic and accurate. Sound stage is out to almost 180 degrees horizontally - over the shoulders in other words. And they measure flat with a little mid range warmth. In summary, so far, my thinking has been supported by my measuring and listening - even a 40 year old pair of speakers can sound great with decent amplification.



One thorn continues to dig into my subjective well being (aka happiness) score however. The base response. Specifically the dynamic attack, or instantaneous peaks, leading edge. Unfortunately I did not take the laptop or microphone to the pick-up as I was merely intending to grab my speakers not spend 6 hours comparing amps. So what follows are subjective observations from a scientific/ engineering POV.

I focused on small sections of tracks, 10 seconds max, set levels of that portion of the track with an SPL meter. Play adjust play adjust then finally get levels the same then loop that portion of the track repeatedly until the brain and ears can identify the differences or lack of same. Many many different types of music but all with a consistent observable difference in the kick drum.

When you look at an audio spectrograph which has deep bass and kick drums, the kick drum frequency extends the total SPL above the continuous bass SPL. The kick drum attack is on top of the bass. It was absent from the AHB2 no matter how I tried different tracks and SPL combinations - turning up the power did not help, although running in mono was much much better (making me think power or current are part of the issue) . A kick drum has a fundamental around 40-100Hz but has mids and highs from 300-1200Hz. The AHB2 could not reproduce the leading edge 'kick' that other amps could. Different speakers, different amps - all managed to deliver some kind of leading edge punch. Even a small studio monitor running off each amp showed a clear difference despite the ease of driving the little speakers (therefore eliminating the amp power etc). Physical cone extension (mentioned in my original post) was much better with AHB2 x 2 in mono, no difference observable between the amps.

When I looked at the impedance curve of the NS-2000 it's dropping from +90 ohms @ 40Hz to 8 ohms @ 100Hz on the woofer. It seems like the speaker is being a little difficult to drive in that area, and the current demand of moving the cone might be beyond the amp. Meaning big magnet, big cone, dropping impedance requiring some decent headroom to deliver an accurate reproduction of the audio signal. As always a pair of headphones can clearly demonstrate what I am talking about compared with a live amp - particularly because it runs though the DAC/ preamp so therefore isolates the amp.



So help me understand and prove my observations. How can I best measure this phenomena? I am thinking REW, microphone 1000mm away from speaker centered on the woofer driver, and then overlay the amplified measurement with original digital audio sample to compare.

And I can also do the test with stereo AHB2 and 2 x mono AHB2's - because the latter is hands down better in this respect despite never clipping in either setup.

As always replicate the test before you comment because if a clueless novice like me can hear and experience the difference someone with professional experience and years of knowledge will probably experience things that I am unaware of...... which may be able to explain what I am experiencing.

Cheers.

P.S. - there are ongoing negotiations re acceptable room treatments - the succulents proved to be both reasonable diffusers and partner permitted additions. Just need to find something thicker on the floor in front of the speakers and something MUCH thicker bushier in the corners for bass traps.

View attachment 64576

Before comparing any amplifier, they should be level matched by playing a sine-wave using a volt meter.
Once level matched, quick switching and single-blind are useful experiments that can be done at home.

Another experiment is to place the AHB2 an a 19x20x10 inch box filled with lead and 100 watt light-bulbs and see which one had greater heft :p

- Rich
 

digitalfrost

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RichB

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It doesn't have auto-on that reacts to music. It only has auto-off that does. Read the manual https://cdn.shopify.com/s/files/1/0321/7609/files/AHB2_Manual_-_Rev_G.pdf?6581480924542235084

It is useless to me. If it had auto-on that reacts to singal, that would be great and I would use it. That said, it uses so little power, I run mine pretty much 24/7.

It looks like this feature is provided to support the EU requirements.
I use triggers on my AHB2. When devices do not have triggers but have USB ports, I have made USB to trigger cables that work with most amps that respond to 5 volts.

My ATI AT522NC has a faulty version of the planet saving auto-off and this amp would not play for more than 10 minutes (trigger or not) without powering off. There was a procedure the disable it that was a bit tricky. I have had the AT522NC repaired.

- Rich
 
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GXAlan

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where the previous amps broken? There should be no audible diffrence!


Not true. Unless you include this in your definition of broken.
 

xaudio

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One thorn continues to dig into my subjective well being (aka happiness) score however. The base response. Specifically the dynamic attack, or instantaneous peaks, leading edge.

Nice setup.

There has been feedback on other forums (possibly here too, not sure) discussing the noticeable benefit, especially in bass response, of vertically bi-amping speakers attached to AHB2s (in stereo mode), such as demonstrated in this graphic: http://www.av2day.com/wp-content/uploads/2014/05/biamp2.jpg

I would suggest experimenting with that, however, I don't believe that model of Yamaha speakers would support such connection.
 
Last edited:

helom

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I have been working on trying to make sense of my subjective observations re the audible and visible discrepancy in AHB2's dynamic performance compared with other amps. Lots of great discussion on here, and interesting insights which have helped me get further with my understanding - and maybe closer to solving the problem. Thanks to all for the contributions - and patience with my sometimes painfully obvious gaps in knowledge.

It's an existential problem this hifi one - sounds good versus is good. I think measurements are a valuable starting point to compare, analyse, understand - but ultimately we listen to music through our ears at home in rooms of questionable acoustical quality. If you measure a difference but are unable to hear a difference it only matters in a subjective way. In other words if you cannot taste the difference between a 25 year old single malt and a blended 25 dollar scotch whiskey - drink and enjoy the 25 dollar one!! Unless your ego or pride dictate otherwise of course. Understanding seems the ideal result of hearing (experiencing) a difference and using measurements to observe the same difference (proving).


A day ago when picking up my 'new' Yamaha NS-2000 speakers I was able to spend some time comparing the rare Harman Kardon Citation XX amplifier with the Benchmark AHB2 x 2 (running in mono) and AHB2 x 1 (running in stereo). The Accuphase P300 from my previous posts was sold unfortunately so not possible to test again.

http://www.thevintageknob.org/harman_kardon-Citation_XX.html

The AHB2 is ground breaking, and this Harman Kardon is another ground breaking amp from a time when product design intent was more closely related to excellence in performance and less to budget and marketing (and warranty) IMO. Meaning that some of these old amps still out-perform many many modern amps designed with modern tools and components. Speakers for example - the Yamaha NS-2000 speakers measure roughly 10-15% less overall than the latest NS-5000 speakers despite almost 40 years separating them and $2.5k v $20k in price respectively.

So while I can somewhat agree to arguments about technological and material advances which have been achieved during the last 40 years, when it comes to open mindedly measuring and listening to different equipment and comparing - much modern equipment is not worth a fraction of the price paid/ asked.

The listening and measuring of the AHB2's with the NS-2000 speakers was very satisfying, the speakers have a reputation for revealing flaws in the audio chain due to their accuracy,clarity, and transparency. Despite the fact they are becoming harder to find, I think the effort was worth it because they seem to be a good match for the AHB2 due to it's exceptional abilities to keep the signal path clean and pure from source to speaker. The speakers have been well voiced to my ears, instruments and vocals are extremely realistic and accurate. Sound stage is out to almost 180 degrees horizontally - over the shoulders in other words. And they measure flat with a little mid range warmth. In summary, so far, my thinking has been supported by my measuring and listening - even a 40 year old pair of speakers can sound great with decent amplification.



One thorn continues to dig into my subjective well being (aka happiness) score however. The base response. Specifically the dynamic attack, or instantaneous peaks, leading edge. Unfortunately I did not take the laptop or microphone to the pick-up as I was merely intending to grab my speakers not spend 6 hours comparing amps. So what follows are subjective observations from a scientific/ engineering POV.

I focused on small sections of tracks, 10 seconds max, set levels of that portion of the track with an SPL meter. Play adjust play adjust then finally get levels the same then loop that portion of the track repeatedly until the brain and ears can identify the differences or lack of same. Many many different types of music but all with a consistent observable difference in the kick drum.

When you look at an audio spectrograph which has deep bass and kick drums, the kick drum frequency extends the total SPL above the continuous bass SPL. The kick drum attack is on top of the bass. It was absent from the AHB2 no matter how I tried different tracks and SPL combinations - turning up the power did not help, although running in mono was much much better (making me think power or current are part of the issue) . A kick drum has a fundamental around 40-100Hz but has mids and highs from 300-1200Hz. The AHB2 could not reproduce the leading edge 'kick' that other amps could. Different speakers, different amps - all managed to deliver some kind of leading edge punch. Even a small studio monitor running off each amp showed a clear difference despite the ease of driving the little speakers (therefore eliminating the amp power etc). Physical cone extension (mentioned in my original post) was much better with AHB2 x 2 in mono, no difference observable between the amps.

When I looked at the impedance curve of the NS-2000 it's dropping from +90 ohms @ 40Hz to 8 ohms @ 100Hz on the woofer. It seems like the speaker is being a little difficult to drive in that area, and the current demand of moving the cone might be beyond the amp. Meaning big magnet, big cone, dropping impedance requiring some decent headroom to deliver an accurate reproduction of the audio signal. As always a pair of headphones can clearly demonstrate what I am talking about compared with a live amp - particularly because it runs though the DAC/ preamp so therefore isolates the amp.



So help me understand and prove my observations. How can I best measure this phenomena? I am thinking REW, microphone 1000mm away from speaker centered on the woofer driver, and then overlay the amplified measurement with original digital audio sample to compare.

And I can also do the test with stereo AHB2 and 2 x mono AHB2's - because the latter is hands down better in this respect despite never clipping in either setup.

As always replicate the test before you comment because if a clueless novice like me can hear and experience the difference someone with professional experience and years of knowledge will probably experience things that I am unaware of...... which may be able to explain what I am experiencing.

Cheers.

P.S. - there are ongoing negotiations re acceptable room treatments - the succulents proved to be both reasonable diffusers and partner permitted additions. Just need to find something thicker on the floor in front of the speakers and something MUCH thicker bushier in the corners for bass traps.

View attachment 64576

Interesting. The AHB2 is producing the best bass I've experienced from an amplifier. The only amps that have come close in my experience happen to be Yamahas.
 

Pjetrof

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Not true. Unless you include this in your definition of broken.


are you serious?
they compare a amp of 15 watt 99 euro to proof a point.
Anyway, each to his own.
For these ears a well made amp not driven in distortion and clipping sound the same.

This forum is all about science, science have proven that the Differences between amps are inaudible.
The only thing some measure better than others!
But the difference is Inaudible.
the benchmark amp is a remarkable product, btw not only the amp, the whole company my opinion.
 

Pjetrof

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“Science, e.g., properly designed double blind testing tests have demonstrated that amplifiers that measure well (low noise and distortion, and enough power and current for a given set of loudspeakers) cannot be distinguished from each other. If you do not understand that fact, you are not accepting of exceptionally strong scientific evidence”

Hope member xulonn don’t mind I use his quote. I want to make my point in proper English!
 

GXAlan

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are you serious?
they compare a amp of 15 watt 99 euro to proof a point.
Anyway, each to his own.
For these ears a well made amp not driven in distortion and clipping sound the same.

We would not complain about a $15 speaker cable being compared to a $1500 speaker cable would we?
What you are saying is that the chip amp is “not a well made amp” and what this site has shown is that price doesn’t correlate with “well made.” From a pure science standpoint, they have reported on objective measurable differences beteeen two amps.

They have stated that a chip amp driving a difficult load that is not clipping nor driven into distortion has a roll off of as much as 5dB starting at 7 kHz which is absent when using a standard hifi amp.

To bring @John_Siau into this, he has stated that amp performance measures differently from a resistive load and a true speaker load. Audioholics clearly subscribed to the belief that all amps sound equal when they are not driven into distortion and clipping which is why they always used a chip amp for convenience when doing their measurements. This data is the first data point I know of where there is arguably a difference.

If someone can get @amirm a Polk L200 to review, I will sponsor a chip amp for comparison.
 

Pjetrof

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I m not an engineer nor a scientist, if audioholics prove that there is audible diffrence that is with this amp and with this speaker.
Maybe this forum and the believers that electronics and cables have inaudible diffrences, have to rethink that.
Also I was referring to the op quote that the benchmark had an audible diffrence with his mola mola Kaluga.
on that quote I asked him sarcastic was the amp broken?
Your quote
“They have stated that a chip amp driving a difficult load that is not clipping nor driven into distortion has a roll off of as much as 5dB starting at 7 kHz which is absent when using a standard hifi amp.“
i shouldn’t t put the price into it, but it is a 15 watt amp compared to an 150 watt amp.
if so, I m not disputing this fact, Cause a tube amp sound different then a solid state amp. So maybe we have to recatogorise amps?
solid state
tube
chip amplifiers
your quote
Audioholics clearly subscribed to the belief that all amps sound equal when they are not driven into distortion and clipping which is why they always used a chip amp for convenience when doing their measurements. This data is the first data point I know of where there is arguably a difference.
that is not true! in the clip he says In the past I ve seen this Behaviour, so he has not the belief that all amps sound equal!
i m sorry can’t bring my point across like I ment to, English not my native language.

i m 52 an had a whole lot op amps and speakers and cables etc.
always believed that my newest sounded best. Until one magical day it didn t sound Good anymore then runnng to the shop and a newer model sounded better.
after years spending ridiculously money on hifi.
speakers plus 50k amps plus 25 k etc come on! Think rational are they made from gold with diamond.
for me ymmv I found sanity, I found ASR the diffrences between electronics maybe they are there or not I don’t care anymore, cause for my ears and being honest to myself I can’t hear them, Instead of buying the next More expensive amp, I drink a glass wine Or 2 and my system sound much better.
 
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RichB

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I have level matched amps using voltmeters and done sighted and unsighted listening tests.
Class A/B's were very close but the ATI AT4000 and AT522NC (Class-D) were distinguishable driving the Revel M20's.

This was enough for me to make a buying decision. YMMV.

- Rich
 

pjug

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We would not complain about a $15 speaker cable being compared to a $1500 speaker cable would we?
What you are saying is that the chip amp is “not a well made amp” and what this site has shown is that price doesn’t correlate with “well made.” From a pure science standpoint, they have reported on objective measurable differences beteeen two amps.

They have stated that a chip amp driving a difficult load that is not clipping nor driven into distortion has a roll off of as much as 5dB starting at 7 kHz which is absent when using a standard hifi amp.

To bring @John_Siau into this, he has stated that amp performance measures differently from a resistive load and a true speaker load. Audioholics clearly subscribed to the belief that all amps sound equal when they are not driven into distortion and clipping which is why they always used a chip amp for convenience when doing their measurements. This data is the first data point I know of where there is arguably a difference.

If someone can get @amirm a Polk L200 to review, I will sponsor a chip amp for comparison.
It is pretty well known that some Class D designs have frequency response that is not flat and load dependent. For example, see here:
https://www.stereophile.com/content/sonic-impact-model-ta2024-super-t-power-amplifier-measurements
Stable frequency response with varying loads is one of the things that make good Class D like Hypex or Purifi good. I'm surprised that Audioholics was using such a cheapo amp for their measurements.
 

Pjetrof

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thx @pjug.
So in normal language a well designed and engineered amplifier working not in clipping or distortion have inaudible differences? Can we say this?
 
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