Benchmark AHB2 power amplifier

Measurements will never tell the whole story of an amps sound signature or performance. Also in general running a stereo amp bridged is a compromise in sound. If you want mono's, get mono's. Don't bridge a stereo amp into mono and think you're making something special, in most if not all cases, you're not.

Let your ears and associated synergy with your other gear be the determining factor.

H9

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Sweet!

Looking forward to reading the review(s) Drew!

After patiently waiting, unsuccessfully, for a used (silver face) AHB2 to appear on the secondary market, I finally decided to pull the trigger on a brand-new unit directly from Benchmark. They had a backlog in orders, but after a two-week wait, mine finally shipped, and arrived a few days later. I paired it with a Benchmark DAC3/HGC preamp.

The only connection option between the two units is balanced XLR, which is perfectly fine with me. I'm using DIY cables from Doug, made with Furez cable, and Vampire Wire XLR plugs. The DAC3/HGC has a few different internal jumper settings for output, depending on the power amp being driven. The setting I had been using for my vintage White Oak Audio Phase Linear 400 amp (-20db) was too weak for the AHB2, so I moved the jumpers to the -0-db setting, and then all was well.

I am technically still in the 'burn-in' phase with my new AHB2, but wow, initial impressions are quite impressive. Before some folks are tempted to say my WOA PL-400 is not really comparative, let me say that I have used several other power amps with the DAC3/HGC. Other power amps used have been as follows: PS Audio S300 (via balanced XLR), McCormack DNA-125, DNA-225, and Symphonic Line RG1MK3. There's a little bit of everything in that bunch, with Class D, Class A/B, and the Symphonic Line which runs heavily into Class A for the first few watts before transitioning to A/B. Believe it or not, the PL-400 with WOA mods had become my personal preference from the lot, but that is another discussion.

It probably goes without saying that the synergy between the Benchmark preamp and power amp is a perfect match, especially with the balanced connections. Noise between the two is non-existent in my estimation, likely due to the fully-balanced connection, and good impedance matching. Digital sources are inherently quiet throughout the chain, so really nothing to discuss there. I currently stream directly via ethernet cable through a Nativ Vita into the DAC3/HGC, plus locally-stored FLAC files on the Vita's internal SSD drive.

For analog playback, I tried vinyl, but have noticed (unexpected) improved results. Maybe I shouldn't be surprised, but my thinking was, "The link between phono-pre and line-stage pre is the same, so why expect an improvement?" Well regardless, it did improve. Perhaps it was due to the true balanced connection between line-level preamp and power amp, or maybe it was purely an improvement in the power amp itself. Regardless of the reason, an improvement was there.

One quick example is from a track on Bruce Springsteen's Tunnel of Love - one of my favorite albums from him - on the fourth track of side one: "Spare Parts". About halfway through the first verse, they add a very funky guitar effect that sounds like a nasty buzzing distortion, but it's actually just an electric guitar sound effect. I initially furrowed my brow when hearing it in its raw form, thinking I had a problem in my system, but once I leaned into it, I realized it was a guitar effect that I just hadn't noticed before. I picked-up on several other musical nuances in that album before hitting that particular track, but wanted to share here that specific example. There are some very good acoustic tracks on that album. And that is part of the intrigue of the AHB2...it plays back musical content in the purest form - warts and all.

That purity of source material and/or equipment seems to be the rub in reviews of the AHB2. It is unforgiving in its replication of material, so flaws in recorded media and/or poorly matched source equipment will be revealed...no doubt. I am currently in the midst of a change from my reference Rogue Audio Triton phonostage, but for this comparison, I stuck with it.

Loudspeakers for my testing are JM Lab/Focal Mezzo Utopia with @VR3 external crossover mods. These are not necessarily difficult to drive, but I think they dip into the 3-4ohm range during low-frequency demands. The AHB2 amp has not struggled at all...in fact, I could not drive it into clipping with my testing...even when I tried hard to do so.

Sonically, my assessment is a very neutral and dynamic power amp, with no limitations that I could effectively test. It is clean from top-to-bottom of the frequency spectrum, with no coloration, and has impressive extensions in both lows and highs...simply no weaknesses. To reiterate, it only accepts balanced/XLR inputs, but has three settings of input level, so experimentation may be necessary, depending on preamp source.

Bottom line is: at the $3,000 brand-new price, I am quite satisfied, and don't see myself selling my unit anytime soon.

Very nice! I like the compact nature of the build as well!

Thanks guys! One design aspect I'm not crazy about is on the rear panel, where they have the inputs placed below the speaker output binding posts.

With that configuration, and the preamp placed above the power amp (as is typical), the input cables and speaker cables have to cross. Of course if the preamp and power amp are side-by-side, it's not as big of an issue.

One interesting thing that happened after swapping power amps actually had to do with my sub-woofer - an SVS SB-2000. The sub is driven (or fed a signal) by the DAC3/HGC preamp, so this is really about the preamp, not the power amp. The DAC3/HGC has two pair of RCA single-ended outputs, and one pair of balanced XLR outputs.

With my existing power amp, I was using one pair of the RCA outputs to feed the power amp, and the other pair to feed the sub. Once I had everything hooked-up with the AHB2 (via XLR) and the sub (via RCA), the output from the sub was suddenly MUCH louder. I thought I had accidentally turned up the volume knob on the back of the sub while switching it off or on, but nope. As I mentioned in my review comments, on my initial listening with the AHB2 in place, the volume output to my loudspeakers was very low. And again, the sub was suddenly very loud. But once I moved the internal jumper in the DAC3/HGC from the -20db setting to the -0- (disabled) setting, everything balanced out - both the loudspeakers and the sub.

I'm not smart enough to understand it, but apparently moving that jumper from -20db to -0- (disabled) had the effect of increasing the output from the XLRs, and lowering the output from the single RCA. But again, with the setting at -20db, it drove both pair of RCA outputs sufficiently. In the DAC3/HGC user's manual, it refers to the jumpers as 'XLR Output Pads', and additionally as 'low-impedance passive pads'. Apparently, using the -10db or -20db settings increases the output impedance slightly. And even though the manual focuses on how these change the XLR outputs, it must also be affecting the RCA outputs as well.