AHB2 and DAC2 HGC Review, Tom Fine, Tape Op



AHB2 - "A Silent Transmitter of Musical Energy"

"Before she joined Jefferson Airplane, Grace Slick was in a band called The Great Society. They made an LP, Conspicuous Only in Its Absence, the title of which has stuck in my mind ever since I first heard it as a teenager."

"That album's title is a perfect description of how the new Benchmark AHB2 power amplifier fits into a studio monitoring system."

"You probably know Benchmark for its long-available ADC and DAC units. The ADC1 analog to digital converter has been used by recordists and mastering engineers for years."

Active vs. Passive Monitors

"Although many studios, particularly smaller at-home outfits, use active monitors (speakers with built-in power amps) ... almost no powered monitors include really super-quality power amps because of the compromises necessary to fit electronics into a speaker cabinet and meet a price point."

"While many of the active monitors get plenty "loud," they often sound un-dynamic and harsh, at least to my ears."

Replacing an Old Workhorse

"I decided to look into modern alternatives to my circa-1980s Audio Design Associates (ADA) FET300 power amp. That amp, designed by ADA co-founder Albert Langella, is built like a tank and has served me without fail since I built my studio almost 20 years ago."

"I thought it was the cat's ass and didn't even consider swapping it out, until I started reading descriptions and reviews of the Benchmark amp."

Benchmark AHB2 Amplifier Technologies

"The patented feed-forward design incorporates an ultra-clean, low-power amplifier that runs in parallel with the main Class AB amplifier, feeding the main output with an error-correction signal that cancels out crossover distortion. Moreover, the power supply is designed to deliver high current on demand, without the need for capacitive storage. The supply responds instantly to the music dynamics, maintaining a constant, well-regulated supply voltage even when challenged with the most difficult peak-power demands."

"Instead of relays, Benchmark chose to use an electronic mute circuit on the output stage to avoid the distortion resulting from high-current relay contacts degrading over time. Gold-plated relays are used on the input stage, where the current is near zero and contact wear is not an issue. When the amp is turned on or off, a very quiet click can be heard."

Amplifier Swap

"As soon as I unplugged the ADA amp and swapped in the Benchmark, it was clear how nice it was to hear less fan noise. I cranked up the monitor volume all the way ... and confirmed there was zero hiss, hum, and other power line hash. I put my ear right to the speakers - still dead silent. The ADA is near-silent but not dead-silent."

"So now, just from being in the system, the Benchmark had taken down the room noise (no fans) and lowered the monitor system noise floor from very quiet to silent."

Listening

"I then started listening to music and other audio - projects I recently completed plus favorite albums. I did this for several weeks, and I also took the Benchmark upstate and plugged it into my B&W 805 Diamond speakers there. In every case, I heard the amp as essentially transparent - a silent transmitter of musical energy."

Adding a DAC2 to the System

"Benchmark also sent me a DAC2 HGC [Tape Op #97] to test drive, and I coupled it with the AHB2 in my big listening room, driving a pair of B&W 808 speakers. This setup replaced a Benchmark DAC1 HDR and an Aragon 8008 amp. Sound- wise, the AHB2 had the same clarifying effect as it had in my other setups. It sounded quicker and crisper with complex and varied dynamics, and it was equally adept at moving the 808's woofers when big bass was happening."

"As happened in the studio, when I swapped the former power amp back in, the sound clouded up a bit, the stereo field narrowed a bit, and I found I wanted to turn the volume knob up a bit because things seemed somewhat muddier."

DAC2 vs. DAC1

"For me, the compelling case for switching to the DAC2 HGC is its feature set. It includes more inputs than the DAC1, and its front panel clearly shows the actual sample- rate being converted to analog (as opposed to what the file or source claims to be), while the DAC1 has no sample-rate readout. Also, the DAC2 HGC's USB port accommodates 192 kHz PCM and native DSD, whereas the DAC1 offers only PCM up to 96 kHz through USB."

"With these upgrades, the DAC2 HGC becomes an obvious candidate for mixing and mastering studios."

Conclusion

"I liked the feature set on the DAC2 HGC enough to buy it for my big listening room, replacing the DAC1 HDR. I bought the AHB2 power amp for my studio and have started filling the piggy bank to buy one for the big listening room."

"Paired with the Amphion Two18 speakers in the studio, the AHB2 is half of the new "Dynamic Duo.""

- Tom Fine, Tape Op

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