Benchmark Media Systems AHB2 Power Amplifier Review

24-bit audio has a dynamic range of 144 dB. 32-bit, 193 dB.

Human hearing? 140 dB. But we remember what scientists said about 20 Hz to 20,000 Hz.

Your SACD recording will have a signal to noise ratio of 120 dB using 1-bit audio and 64x over-sampling. This is equivalent to a recorded bit-depth of 20 bits. That 120 dB* is also what you would hear on a very good system today, with a CD utilizing dither.

Today's DAC's have a signal to noise ratio (SNR) of about 21-bit, typically. This equates to 124 dB.
This is what you would hear, reading Wikipedia.

Now, some rise above. The Trinity DAC is well-regarded as one of the best DAC's in existence. This is not a specifications champ, but it is well-measured. Users throw out their entire top-line DCS for a single Linotech DAC.

On the topic of 24-bit audio as a preface to the Benchmark AHB2 is MSB. While not hitting 32-bits, the MSB Select DAC II ($89,950.00 USD, $127,840.00 USD) hits an effective resolution of near 29-bit (28.5) or 173 dB. We would be remiss not to mention their MSB Diamond DAC V ($29,995.00 USD, $58,758.00 USD) which actually hits (exceeds) 24-bits (24.5) or 149 dB. Mola Mola? 140 dB. Just a touch, under '24. By 4 dB, or a shy away 9 dB from the MSB DD V.

This is top-of-the-road performance.

Advertorial: most users would be fully satisfied with the MSB Analogue DAC ($6,995.00 USD, $19,543.00 USD) in their system (20.8 bit resolution, 127 db), or one of the DAC's by Benchmark Media Systems.

A DAC like the DAC2 HGC ($1,995.00 USD) for the most-appropriate exemplar of a modern-day DAC (multiple DAC's per channel) by Bechmark Media Systems that both Stereophile and TAS took far too long to look at and mention, in print, and on-line.

This world-leading (the best that a headphone enthusiast like Ken Rockwell will get as a reference) DAC offers a signal to noise ratio of 123 dB or around 20-bit or 21-bit (126.42 dB), if A-weighted.

Let's talk about THD (not THC), also. Equivalent to smoking, THD (Total Harmonic Distortion) lowers that already good Signal-to-Noise (SNR) of the Benchmark DAC2 HGC to 108 dB, full-spectrum. Or 109 dB, if measured at 1 kHz.

So we know what we are talking of. It's not a pretty picture, but my it sounds lovely.

Let's get to the AHB2, then.

The Benchmark Media Systems AHB2 Power Amplifier ($2,995.00 USD) is a piece of Hi Fi Art from the rear, and not so good-looking from the front. You'd almost imagine it on a music stand, somehow, replacing the conductor. Let's get to a comparison with Burson, later.

There are some who would say that power would have an effect, adversely.

On thing about about the Benchmark AHB2 is the specification. This is an amp you wish was a little bigger, and had much, much more power.

Something around 1000 watts per channel at 8-ohms to compete with the Bryston 28B SST2.

Now the Benchmark AHB2 Power Amplifier is rated at 100 watts per channel, in stereo, or 200 watts, mono. That's in 16-ohms, mind-you.

So it's under-powered we would say for practical purposes by 10 times. What does this mean in real-world terms?

The most reasonable comparison would not be 100-watters, but the Musical Fidelity M8-700M Power Amplifier ($12,500.00 USD / pair) - also short by about 300 watts.

It's rated, Signal to Noise 120 dB. This is a reasonable and decent specification. For 16-bit (96.33 SNR) audio, 20-bit will do.

Benchmark's AHB2: 130 dB. There's an extra-bit there. [2-bits, if you are generous..] 21-bit is fine.

Let's look at power.

The Benchmark will deliver 380 watts in bridged-mono, RMS. It will no do so well into lower impedances, in this mode, and will deliver 200 watts into 16 ohms.

This isn't a bad amount: more than half of the M8-700M's 700 watts per side.

In his review of the Benchmark AHB2, Kalman Rubison says that it drives his B&W 800 Loudspeakers to aplomb.

So, you have in essence, a 21-bit Power Amplifier. It's digital to the rescue.

Grim Audio has a way of getting into the business.


Typically, noise will have a factor (noise-floor) in room, unless masking is done (headphones, 30 dB).





*A Sony SBM (Super Bit Mapping) CD, for example.
+ Though not providing good specifications (SNR 117 dB, 24-bit 192 kHz, 20Hz-20Khz, +/-0.1dB, 0.5Hz-200KHz, -1dB, THD < 0.006%) the Schitt Audio YGGDRASIL ($2,299.00 USD) is a contemporary 21-bit DAC (via 2-DAC's locked per channel).