![]() So has The Force succeeded in beating the Amplifier Empire? Did The Force awaken new audio capability in old AB design? Can the AHB2 do the Kessel Run in under 12 parsecs? However, the mono switch should also work. Benchmark’s can make cables with bananas or spades on the speaker end against a special order. Biamping is also possible but will require NL4 4-pole cables. The power output goes from 100 W/channel to 380 W single channel. The AHB2 can be bridged and operated as a monoblock. Play “Girl from Ipanema” and if Gertrud is MIA you are running mono (guess how I know…). The unit puts out only one channel on both speakers in this case. On the opposite side there is a Bridge to Mono switch which can easily be mistaken for the gain switch. Switching to a higher gain is easy with the toggle switch on the back in case the recording is very quiet and needs higher volume is needed. Most SACD and downloaded audio files had enough output voltage to play very loud. I ran the AHB2 on the lowest gain which works well with the Benchmark DAC2 and also my Oppo BDP-105 which has volume output control. Benchmark recommends using the lowest practical gain for optimum sound. The lowest gain is for studio equipment that have high input levels. The input amp has 3 levels of gain, 22 dBu, 14.2 dBu and 8.2 dBu for low, mid and high gain. To recapitulate, the AHB2 is actually three amplifiers: a 3 stage input amp, an AB main amp and an amp to control and compensate for distortion. The AHB2 responds well to cable upgrades but Benchmarks standard cables are a good starting point. After three days on my Cable Cooker they were actually quite nice – especially considering the price of $38 each or $76 per pair. I used Benchmark’s XLR cables which initially sounded questionable. Otherwise you may need to revise the upstream equipment. The amp should really be fed a balanced signal for best performance – which is not a problem if your current equipment, including high-end cables, are balanced. I tried my own XLR-RCA adapters but the result was less than excellent. Benchmark suggests adapters for single ended RCA cables. Distortion – the key feature of the amplifier – is < -118 dB N+THD in Stereo Mode, while S/N is 132 dB A-weighted. Frequency response is a wide 0.1 Hz – 200 kHz +/- 3dB. The output is rated as 100 W/channel into 8 Ohms, 190 W/channel into 4 Ohms and 380 W bridged Mono into 8 Ohms. It’s exactly the size of a standard letter page – 8.5”x11” – and weighs 12.5 lbs. The AHB2 is a very compact and light weight amplifier. Benchmark claims that there is no sagging in internal voltage during high loads or when line voltage dips. The AHB2 power supply is regulated and very efficient in combination with the H Class rails. Switching power supplies are much more efficient, and smaller, than linear transformer based supplies but traditional designs (or wall-warts) are noisy and can affect power demand. ![]() The switching is carried out at frequencies well above the audio band to reduce any audible artifacts from the power supply. The AHB2 has a resonant zero-voltage switching power supply. Benchmark’s clever design compensates for this with the Class A amplifier. To provide high current on demand the H rails have to shift between stages which can ripple through as distortion. Here again the battle is between efficiency and distortion. The Force also works on the H Class power rail system. In addition, there’s a 3D amplifier that boosts the input signal in 3 selectable levels. The Force runs in parallel with the regular AB amplifier attack fleet and corrects mistakes and shores up any weakness caused by non-linearity in the transition stage. To win this battle the rebel alliance, i.e., THX and Benchmark, are trusting The Force (my name – not the official designation) in the shape of a low power Class A correction amplifier. The Dark Side in the amplifier war is distortion and heat. Class H tracking rails deliver power on demand unlike linear power supplies that must have stand-by capacity. AB amplifiers are more efficient than Class A by utilizing a push-pull transition.Ĭlass AB has two circuits to increase efficiency over A – straight amplification – and class B where ½ of the signal is used. It’s basically an AB amp with a class H power rail arrangement. The AHB2 is an attack on current amplifier design. Achromatic may mean colorless or neutral or without modulation. The design is called Achromatic Audio Amplifier. THX has patented a novel amplifier design, THX AAA Technology TM and Benchmark Media Systems has turned it into a new power amplifier – AHB2. The company is a technology spin-off from Lucasfilm, which originated the Star Wars movie series. There’s a new actor in the high end audio amplification field – THX.
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