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Benchmark AHB2 Review (Updated Measurements)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 7 2.3%
  • 2. Not terrible (postman panther)

    Votes: 5 1.7%
  • 3. Fine (happy panther)

    Votes: 47 15.6%
  • 4. Great (golfing panther)

    Votes: 243 80.5%

  • Total voters
    302

amirm

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Back in 2019, I reviewed the Benchmark AHB2 Stereo Amplifier. I received a second sample from a kind member to update the measurements. Originally the AHB2 cost $3000 but now, $3,500.
Benchmark AHB2 Stereo Bridge THX Power Amplifier Review.jpg

As you see, it is a compact but very nice looking amplifier. I appreciate the clipping indicator which seemed accurate in testing. Back panel shows both SpeakOn and traditional binding posts:
index.php


In my original testing, I used the SpeakOn connectors as that gave better response than the binding posts. They are directly soldered to the PC Board as opposed to extra wiring. The amplifier is so low distortion and sensitive to load modulation that this makes a difference as you see below.

A very nice feature is three different gain settings. Highest saturates around 2 volts, middle 4 volts and lowest around 10 volts. I measured all three in areas that matter.

You can also bridge the amplifier into mono and get massively more power. Again, see below.

Benchmark AHB2 Amplifier Measurements
Let's start with our usual dashboard in low gain:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain Measurement.png

While this is phenomenal performance, we have gone from SINAD of 113 dB to 111 dB. This is due to third harmonic rising (inconsequentially to -120 dB). So ranking goes down a bit:
Best stereo amplifier review 2024.png

Best stereo amplifier review zoom 2024.png


Surprisingly, there is not much degradation at higher gain levels:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Medium Gain Measurement.png

Benchmark AHB2 Stereo Bridge THX Power Amplifier HIgh Gain Measurement.png


This is reflected in the SNR:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain SNR Measurement.png

Benchmark AHB2 Stereo Bridge THX Power Amplifier Medium Gain SNR Measurement.png

Benchmark AHB2 Stereo Bridge THX Power Amplifier HIgh Gain SNR Measurement.png


I did discover some load dependency:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain Frequency Response Measurement.png

It is well managed though and is outside of audible band.

Intermodulation distortion is expectedly low:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain Multitone Measurement.png

Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain 19 20 kHz Measurement.png


Crosstalk is a hair worse which could be the different speaker wiring:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain Crosstalk Measurement.png


Let's run our 4 ohm power sweep at all three different gains:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Power 4 ohm Measurement.png

You see again the impact of the speaker binding vs SpeakOn. But still excellent performance.
Benchmark AHB2 Stereo Bridge THX Power Amplifier Max and Peak Power 4 ohm Measurement.png

The dependency on wiring goes down at 8 ohm due to lower currents involved:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Power 8 ohm Measurement.png


Changing frequencies doesn't impact the amplifier power sweep much except at 15 kHz, and even there it is well behaved:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Power vs frequency vs distortion Measurement.png

Some of the non-linearity may again be due to binding posts.

Amplifier is stable and performant on power up:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Low Gain Warm up Measurement.png


Benchmark AHB2 Bridge Mode Power Measurements
The amplifier goes into differential mode which in theory quadruples the power. It is however only rated above 6 ohm. I tested it at 8:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Max and Peak Power 8 ohm Bridged Measurement.png


Benchmark AHB2 Reactive Power Measurements
Using my Loadbox, I tested the amplifier at different complex and resistive loads down to 2 ohm:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Power Reactive Load Measurement.png


There is a bit of voltage droop as we go down from 8 ohm but still respectable when you consider how much power is being pumped out (approximately):
Benchmark AHB2 Stereo Bridge THX Power Amplifier Power Reactive Load Watts Measurement.png


Here is the same but in bridged mode:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Max and Peak Power 8 ohm Bridged reactive Mea...png

As you see, it also doesn't have any issues with reactive/complex loads.

EDIT: forgot to post the pop measurements:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Power on pop Measurement.png


Conclusions
Using standard binding posts reduces performance just a bit but certainly nothing to worry about. What we have is still state of the art and one of best ever consumer stereo amplifiers produced.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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DHT 845

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Really? Nasty 3k spike due to "traditional binding posts"?
As far as multitone concerned Soncoz SGP1 seems to be better and for less than 1/3 of the Benchmark's price (not to mention Topping LA90 discrete).
 
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amirm

amirm

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What type of connector did you use on the binding post for this test? I've got the recommended locking banana plugs in a bag but I've been lazy connecting them...
I use locking ones.

Here are the Specifications for the Amplifier. As expected they are detailed and lengthy:

Manufacturer Specifications:

Continuous Average Output Power​

< 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz

  • 100 Watts per channel into 8 Ohms, both channels driven
  • 130 Watts per channel into 6 Ohms, both channels driven
  • 190 Watts per channel into 4 Ohms, both channels driven
  • 240 Watts per channel into 3 Ohms, both channels driven
  • 200 Watts into 16 Ohms, bridged mono
  • 380 Watts into 8 Ohms, bridged mono
  • 480 Watts into 6 Ohms, bridged mono
All speakers have variations in input impedance. Select loads based on nominal impedances not minimum impedances. The AHB2 is stable into all loads. The AHB2 is conservatively rated at an output level where THD+N is < 0.0003 % instead of the more typical 1% THD+N. Power at 1% THD will be higher.

Output Voltage Into Various Load Impedances​

< 0.0003 % THD+N at the following output voltages and load impedances, 20 Hz to 20 kHz

  • 29.03 dBV, 31.25 dBu, 28.28 Vrms into 8 Ohms, both channels driven
  • 28.92 dBV, 31.14 dBu, 27.93 Vrms into 6 Ohms, both channels driven
  • 28.81 dBV, 31.03 dBu, 27.57 Vrms into 4 Ohms, both channels driven
  • 28.57 dBV, 30.79 dBu, 26.83 Vrms into 3 Ohms, both channels driven
  • 27.14 dBV, 29.36 dBu, 22.76 Vrms into 2 Ohms, both channels driven
  • 35.05 dBV, 37.27 dBu, 56.57 Vrms into 16 Ohms, bridged mono
  • 34.83 dBV, 37.05 dBu, 55.14 Vrms into 8 Ohms, bridged mono
  • 34.59 dBV, 36.81 dBu, 53.67 Vrms into 6 Ohms, bridged mono
  • 33.16 dBV, 35.38 dBu, 45.52 Vrms into 4 Ohms, bridged mono
Use dBV to calculate the peak SPL from your speaker/amplifier combination. Use the following formula: Amplifier output voltage in dBV + speaker sensitivity at 2.83V - 9 dB. Example: (29.03 dBV at 8 Ohms) + (90 dB SPL @ 2.83V 1m) - 9 dB = 110 dB SPL at 1 meter

SNR & Dynamic Range​

Rated output relative to output noise, inputs shorted

  • 132 dB A-weighted, Stereo Mode
  • 135 dB A-weighted, Mono Mode
  • 130 dB Unweighted, 20 Hz to 20 kHz, Stereo Mode
  • 133 dB Unweighted, 20 Hz to 20 kHz, Mono Mode

Noise Voltage​

Output noise voltage, A-weighted, inputs shorted

  • -103 dBV, -101 dBu, 7.1 uVrms, Stereo Mode
  • -100 dBV, -98 dBu, 9.8 uVrms, Mono Mode
Use dBV to calculate the SPL of the noise produced by your speaker/amplifier combination. Use the following formula: Amplifier output noise voltage in dBV + speaker sensitivity at 2.83V - 9 dB. Example: Mono mode driving very high efficiency speakers: (-100 dBV) + (104 dB SPL @ 2.83V 1m) - 9 dB = -5 dB SPL at 1 meter. This means that the system noise will be 5 dB below the threshold of hearing when driving speakers with a very high 104 dB efficiency.

Noise Relative to 2.83 Vrms​

Output noise relative to 2.83 Vrms, A-weighted, inputs shorted

  • -112 dB, Stereo Mode
  • -109 dB, Mono Mode

THD+N​

1 kHz, 80 kHz LPF, at full rated output into any rated load

  • < -118 dB (< 0.00013%), Stereo Mode
  • < -118 dB (< 0.00013%), Mono Mode

THD​

1 kHz, 20 kHz LPF, at full rated output into any rated load

  • < -119 dB (< 0.00011%), Stereo Mode
  • < -120 dB (< 0.00010%), Mono Mode

Crosstalk​

  • Better than -115 dB at 1 kHz
  • Better than -92 dB at 20 kHz

Frequency Response​

  • Better than 0.1 Hz to 200 kHz, +0/-3 dB
  • -0.01 dB at 20 Hz, -0.17 dB at 20 kHz, 8-Ohm Load
  • -0.23 dB at 20 Hz, -0.32 dB at 20 kHz, 4-Ohm Load

Damping Factor​

  • 350 at 20 Hz, 8-Ohms
  • 254 at 1 kHz, 8-Ohms
  • 34 at 20 kHz, 8-Ohms
  • 7 at 200 kHz, 8-Ohms

Maximum Audio Output Current​

  • 29 A peak, per channel, both channels driven

Input Sensitivity​

  • Low-Gain = 22 dBu (9.8 Vrms), Gain = 9.2 dB
  • Mid-Gain = 14.2 dBu (4 Vrms), Gain = 17.0 dB
  • High-Gain = 8.2 dBu (2 Vrms), Gain = 23 dB
  • Use Mid-Gain or High-Gain settings for unbalanced inputs
  • Unbalanced inputs require RCA to XLRM adapter cables

Input Impedance​

  • 50 k Ohms, normal mode
  • 1 M Ohm, common mode

Input CMRR​

  • 80 dB at 20 Hz, typical
  • 80 dB at 1 kHz, typical
  • 65 dB at 20 kHz, typical

Trigger I/O​

  • 12 VDC 200 mA current-limited output to trigger turn-on of remote devices
  • DC input for slaving to remote devices
  • Input responds to 3.3 V logic and higher, VIL = 1.26 V, VIH = 2.7 V
  • Absolute maximum input voltage = 30 VDC
  • Absolute minimum input voltage = -0.3 VDC
  • Input Impedance = 20 k Ohms

Protection Circuits​

  • Fully Electronic, No Relays
  • Mute Sequencing
  • Distortion Detection
  • Short Circuit Detection
  • Over Current Detection
  • Over Temperature Detection
  • SOA Detection (Output device safe operating area)

Dimensions​

Non-rack-mount version:​

  • 11.04" W x 3.88" H x 9.34 " D - Including feet and binding posts
  • 11.04" W x 3.47" H x 8.33 " D - Excluding feet and connectors
  • Faceplate height is 2RU

Rack-mount version:​

  • 19.00" W x 3.88" H x 10.62 " D - Including binding posts, handles and removable feet
  • 19.00" W x 3.47" H x 8.33 " D - Excluding feet and connectors
  • 9.09" rack depth, including binding posts, excluding cables
  • 11" rack depth, including cables
  • Faceplate height is 2RU

Weight​

  • 12.5 lbs., 16 lbs. shipping - Non-rack-mount version
  • 13.5 lbs., 17 lbs. shipping - Rack-mount version

AC Input​

  • Auto-ranging AC Input
  • 100 to 120 VAC +/- 10%, 8 Amps, 50 - 60 Hz
  • 220 to 240 VAC +/- 10%, 8 Amps, 50 - 60 Hz
  • Idle Power Consumption = 20 W
  • Standby Power Consumption < 0.5 W
 
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musicforcities

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I hope this will not get used as evidence for expensive audiophile connectors.
Speakons are professional connectors. Not an esoteric audiophile thing. They are engineered to have consistent and reliable contact even with frequent connection/disconnection cycles. They lock by design, in the way male and female terminations are designed (unlike “locking” banana plugs which just apply pressure at the male jack (and not always in a way that makes for consistent or all that great contact. They are also inexpensive compared to many of the “high end” binding posts and jacks out there. Though they do take a bit more room than smaller binding posts.

In a more sane world speakons would be the standard connection, as would balanced xlr instead of RCA, or at least unbalanced with BNC or DIN terminations. But there you go.

Lastly as Amir noted, the speakon are directly pcb mounted on this case. while the posts require wiring, soldering etc that is more prone to variation, etc.

Not that it matters because whether one uses the jacks or speakons the difference is not audible and the amp is stunning.

Though I would hazard that there seem to be purifi and ncore amps that offer far better watts per dollar with measurements close enough to this one to be rather moot.
 

DHT 845

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musicforcities

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Still a great amp. Too bad it costs so much!
The volume has to be tiny and QC tolerances must be very rigorous. It’s built to last decades and maybe could be passed down to your children if properly maintained. Also, people who designed and built this deserve a living wage.

This ain’t a mass-market AVR assembled in an enormous factory by robots with parts selected for post-warranty obsolescence and landfills.

Amortize the price by a reasonable number
of years of use before major service and it’s probably quite cheap. And I best resale value is very good in five years or ten or 15-20 when it will be considered one of the last great CLASS AB amps ever made.

a quality purifi or ncore amp may have similar or better amortized lifecycle costs, though I suspect power supplies may not age as well.

One can easily drop the same amount on a fancy but not great avr that will be obsolete whenever Dolby comes out with a new whiz-bang codec or HDMI standards shift.
 

capslock

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How did the Topping PA5 II get dropped from the best of bargraph in this review?
 

pogo

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Here is the same but in bridged mode:
Benchmark AHB2 Stereo Bridge THX Power Amplifier Max and Peak Power 8 ohm Bridged reactive Mea...png

As you see, it also doesn't have any issues with reactive/complex loads.
What would it look like at 4ohm?
 
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amirm

amirm

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What would it look like at 4ohm?
Manual warns against going that low and didn't want to chance damaging it.
 
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