Review and Measurements of Benchmark AHB2 Amp

[RichB]

It doesn't seem to be that simple in reality and is probably also design-dependent. What has also been observed, is that at constant load, for example, 8ohms but different volumes, the DF can change!

True. Amplifiers are not typically measured for impulse response.
Stereo.de has a measurement that is not typical for DF.

Damping factor is traditionally measured at 1W ([email protected]).

Whatever, they are doing, it is not comparable to manufacturer DF specifications, though we cannot be sure of those either, especially, when they do not provide frequency. Benchmark provides this data in detail.

Stereophile, choses to measure their amps into a standard simulated load. Unfortunately, they apply inconsistent scales, making it difficult to compare.
Here is an example that compares the AHB2 to the Gryphon Apex Stereo because it is a recent review of a stratospheric price point.

Benchmark ($2999): https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-measurements

The output impedance, including a 6' speaker cable, was a low 0.09 ohm at 20Hz and 1kHz, rising slightly to 0.22 ohm at 20kHz. As a result, the modification of the Benchmark amplifier's frequency response due to the interaction between this impedance and that of our standard simulated loudspeaker was just ±0.1dB

Gryphon Apex Stereo ($99,000): https://www.stereophile.com/content/gryphon-apex-stereo-power-amplifier-measurements

Gryphon specifies the Apex's output impedance as 0.015 ohms. My measurement was slightly higher in the right channel, at close to 0.05 ohms (including the series resistance of 6' of speaker cable), and significantly higher in the left channel, at 0.17 ohms.

The AHB2 stated output impedance is 0.09 at 20Hz and 0.22 at 20kHz.
The Apex stated output impedance is 0.015.
Unfortunately, Stereophile is inconsistent with graph scale.

Speakers also vary in load, including effect load, eyeballing the graphs.
Into 2 Ohms, the AHB2 is down 0.25 dB at 20Hz and 0.75 at 20Khz.
Into 2 Ohms, the Apex is down 0.4 dB at 20Hz and 0.6 dB at 20kHz.

Here is the AHB2 speaker load measurement squished in paint to be approximately the same scale:

If you want to look for indicators for bass performance, you might want to look into linearity into load.

Stereophile has measured the NAD M33 integrated amp ($4999).

The M33's output impedance at the speaker terminals was a low 0.08 ohm at 20Hz and 1kHz, rising to 0.1 ohm at 20kHz. (These values include the series impedance of 6' of spaced-pair loudspeaker cable.) Fig.1 shows the frequency response at the speaker outputs, with the M33's A/D converter set to its maximum sample rate of 192kHz. Unlike the M32, where a peak developed at the top of the audioband, especially into higher load impedances (footnote 1), the M33's audioband output is flat and rolls off above 20kHz, reaching –3dB at 55kHz. However, note the imbalance between the channels, with the left channel (blue and cyan traces) 0.6dB higher in level than the right (red and magenta).

The AHB2 stated output impedance is 0.09 at 20Hz and 0.22 at 20kHz.
The M33 stated output impedance is 0.08 at 20Hz and 0.1 at 20kHz.

Into 2 Ohms, the AHB2 is down 0.25 dB at 20Hz and 0.75 at 20Khz.
Into 2 Ohms, the M33 is down 0.65 dB at 20Hz and 0.85 at 20kHz.

If you have difficult effect load, clearly the AHB2 will perform better despite the AHB2 maximum DF is 350 and the M22 spec is >800.
Given the Stereophile measurements, you are more likely to have reduced bass in a difficult to drive speaker in the M33 than the AHB2. Even the $99,000 Apex is bested, in linearity into load...

- Rich

 

[SIY]

True. Amplifiers are not typically measured for impulse response.
Stereo.de has a measurement that is not typical for DF.


Whatever, they are doing, it is not comparable to manufacturer DF specifications, though we cannot be sure of those either, especially, when they do not provide frequency. Benchmark provides this data in detail.

Stereophile, choses to measure their amps into a standard simulated load. Unfortunately, they apply inconsistent scales, making it difficult to compare.
Here is an example that compares the AHB2 to the Gryphon Apex Stereo because it is a recent review of a stratospheric price point.

Benchmark ($2999): https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-measurements

View attachment 232310

Gryphon Apex Stereo ($99,000): https://www.stereophile.com/content/gryphon-apex-stereo-power-amplifier-measurements

View attachment 232312
The AHB2 stated output impedance is 0.09 at 20Hz and 0.22 at 20kHz.
The Apex stated output impedance is 0.015.
Unfortunately, Stereophile is inconsistent with graph scale.

Speakers also vary in load, including effect load, eyeballing the graphs.
Into 2 Ohms, the AHB2 is down 0.25 dB at 20Hz and 0.75 at 20Khz.
Into 2 Ohms, the Apex is down 0.4 dB at 20Hz and 0.6 dB at 20kHz.

Here is the AHB2 speaker load measurement squished in paint to be approximately the same scale:
View attachment 232314

If you want to look for indicators for bass performance, you might want to look into linearity into load.

Stereophile has measured the NAD M33 integrated amp ($4999).

View attachment 232315

The AHB2 stated output impedance is 0.09 at 20Hz and 0.22 at 20kHz.
The M33 stated output impedance is 0.08 at 20Hz and 0.1 at 20kHz.

Into 2 Ohms, the AHB2 is down 0.25 dB at 20Hz and 0.75 at 20Khz.
Into 2 Ohms, the M33 is down 0.65 dB at 20Hz and 0.85 at 20kHz.

If you have difficult effect load, clearly the AHB2 will perform better despite the AHB2 maximum DF is 350 and the M22 spec is >800.
Given the Stereophile measurements, you are more likely to have reduced bass in a difficult to drive speaker in the M33 than the AHB2. Even the $99,000 Apex is bested, in linearity into load...

- Rich

And this is why marketing specs like DF are absolutely useless.

 

[617]

People complain about McIntosh making the same-old amp but look at what happens if you truly innovate - you attract people who scrutinize the product to a ridiculous degree even when you make the best amp on the market.

 

[pjug]

View attachment 232315

The AHB2 stated output impedance is 0.09 at 20Hz and 0.22 at 20kHz.
The M33 stated output impedance is 0.08 at 20Hz and 0.1 at 20kHz.

Into 2 Ohms, the AHB2 is down 0.25 dB at 20Hz and 0.75 at 20Khz.
Into 2 Ohms, the M33 is down 0.65 dB at 20Hz and 0.85 at 20kHz.

Take note, though, that on the M33 curves there is a channel imbalance, so at 2 ohms it is down about 0.45dB (green compared to red). Also I think that Stereophile measurements for this graph include speaker cable resistance, so the drop just from amplifier output impedance would not be this much. But still I wonder what is up with the M33 (or that sample, or the measurement). A Purifi amplifier should do better. See this measurement of the C298 by Soundstage (curves are 8R, real speaker, 4R, and 2R):

SoundStageNetwork.com | SoundStage.com - NAD C 298 Stereo Amplifier Measurements

www.soundstagenetwork.com

 

[SIY]

Take note, though, that on the M33 curves there is a channel imbalance, so at 2 ohms it is down about 0.45dB (green compared to red).

What am I missing? The channel imbalance looks about 20 times lower than that.

 

[RichB]

Take note, though, that on the M33 curves there is a channel imbalance, so at 2 ohms it is down about 0.45dB (green compared to red). Also I think that Stereophile measurements for this graph include speaker cable resistance, so the drop just from amplifier output impedance would not be this much. But still I wonder what is up with the M33 (or that sample, or the measurement). A Purifi amplifier should do better. See this measurement of the C298 by Soundstage (curves are 8R, real speaker, 4R, and 2R):

SoundStageNetwork.com | SoundStage.com - NAD C 298 Stereo Amplifier Measurements

www.soundstagenetwork.com

It is good to acknowledge that speaker cable affects DF blunting the impact.

The source of the drop in the Stereophile measurements is not unusual and most folks use at least 6' of speaker wire so the test is sensible.
The measurements were provided to show how load impedance can have a more significant impact on linearity than the specified DF.
The Stereophile data makes that evident.

Soundstage is a different amplifier so no meaningful conclusion can be drawn.

I see no reason to start discussions of additional amplifiers on the AHB2 thread that have no bearing on its performance.
You seem to have little interest in this amp, so what's the point?

- Rich

 

[pjug]

What am I missing? The channel imbalance looks about 20 times lower than that.

The channel imbalance in the Stereophile M33 measurements, not the C298. JA mentions it in the text.

 

[pjug]

It is good to acknowledge that speaker cable affects DF blunting the impact.

The source of the drop in the Stereophile measurements is not unusual and most folks use at least 6' of speaker wire so the test is sensible.
The measurements were provided to show how load impedance can have a more significant impact on linearity than the specified DF.
The Stereophile data makes that evident.

Soundstage is a different amplifier so no meaningful conclusion can be drawn.

I see no reason to start discussions of additional amplifiers on the AHB2 thread that have no bearing on its performance.
You seem to have little interest in this amp, so what's the point?

- Rich

Was just wondering if something is off on the M33 measurements you posted, not trying to rebut your point or say anything negative about the AHB2. I thought the cat was out of the bag regarding discussion of other amps, although maybe you are right about that.

 

[SIY]

The channel imbalance in the Stereophile M33 measurements, not the C298. JA mentions it in the text.

The M33 I tested was within 0.02dB channel match.

Fresh From the Bench: NAD Electronics M33 Masters BluOS Streaming DAC Amplifier

After reviewing the compact but mighty M10 Masters Series streaming amplifier from NAD Electronics, Stuart Yaniger simply had to try the new flagship NAD M33 Masters streaming DAC amplifier. This was the first mainstream product to implement the Purifi Audio Eigentakt (self-clocking) amplifier...

audioxpress.com

 

[dan_uk]

Hi - Can anyone with an AHB2 tell me how big the box is? I'm thinking of taking one home as hand luggage on my next US trip

 

[The Equalizer]

Hi - Can anyone with an AHB2 tell me how big the box is? I'm thinking of taking one home as hand luggage on my next US trip

The box mine came in measures 15.5 x 13 x 6.75 inches / 39.4 x 33 x 17.1 centimeters (L x W x H).

 

[dan_uk]

The box mine came in measures 15.5 x 13 x 6.75 inches / 39.4 x 33 x 17.1 centimeters (L x W x H).

Thank you.... Sounds like hang luaggage to me!

 

[misterdog]

Might as well get a pair then
Though the £ V $ is at a 37 year low.

 

[dan_uk]

Might as well get a pair then
Though the £ V $ is at a 37 year low.

Yes, I just noticed that this morning, it's awful in fact... Has put me off the idea... I'm not visiting the US until Christmas, a slight chance it may improve by then.

 

[HarmonicTHD]

Yes, I just noticed that this morning, it's awful in fact... Has put me off the idea... I'm not visiting the US until Christmas, a slight chance it may improve by then.

Unlikely.

But the Audiophonics option is not outright appalling either.

 

[misterdog]

I think Audiophonics don't stock the AHB2, Thomann does, though not currently in stock and is cheaper than the UK list price.

Thomann - Welcome Home!

Search Results - Page 1

www.thomann.de

Still £ 700 cheaper in your hand luggage.

 

[Frontino]

I don't understand the THD+N vs Hz image: it shows the amp going into protection mode at 45 Hz at just 8 V, which should be 16 W at 4 Ohm (so, why does @amirm indicate 133 W?).

Thing is, Stereophile, with same test at 15.4 V, do not trigger it.

What am I missing?

 

[DonH56]

I don't understand the THD+N vs Hz image: it shows the amp going into protection mode at 45 Hz at just 8 V, which should be 16 W at 4 Ohm (so, why does @amirm indicate 133 W?).

Thing is, Stereophile, with same test at 15.4 V, do not trigger it.

What am I missing?

Can you link to the image? Or at least which post? I am not seeing that...

 

[HarmonicTHD]

I don't understand the THD+N vs Hz image: it shows the amp going into protection mode at 45 Hz at just 8 V, which should be 16 W at 4 Ohm (so, why does @amirm indicate 133 W?).

Thing is, Stereophile, with same test at 15.4 V, do not trigger it.

What am I missing?

I don’t see it either.

 

[Frontino]