Diego Estan was recently assigned the unenviable task of reviewing Anthem’s STR preamplifier ($3999 USD) for sister site SoundStage! Access.

Unenviable? Anyone who wants to thoroughly review the Anthem STR has to write a lot. The STR is not only a robust analog preamplifier with plenty of inputs and an astonishing number of customization options, it also contains a topflight DAC section with a rich feature set of its own, a phono stage compatible with moving-magnet (MM) and moving-coil (MC) cartridges, an analog-to-digital converter, a powerful DSP engine, Anthem’s proprietary Anthem Room Correction (ARC) Genesis processing, and the most advanced support of subwoofers I’ve seen in any hi-fi product. A lot.

We published Diego’s review on March 15. To shorten it to a more easily digestible length, we excerpted from it what became two other articles about the STR, and published them on Access before the review proper. One was about how Diego set up his subwoofers and loudspeakers with the STR; the other concerned the STR’s unique phono capabilities, in which the signals can be left in the analog domain, or converted to digital and subjected to further tweaking of equalization and/or ARC processing.

I think Diego did a great job of completing a tough assignment. His three pieces thoroughly assess the STR, touching on all of its main features in considerable detail. And that should’ve been that.

But it wasn’t. After he’d finished but before his review was published, Diego dropped off the STR at my place so that I could photograph it. When I’d taken its picture, I inserted it in my reference system. At the time, that system included Vivid Audio’s fabulous Giya G2 Series 2 speakers driven by Constellation Audio’s Revelation Taurus mono amplifiers via QED Supremus speaker cables, and with a set of Crystal Cable’s Standard Diamond balanced interconnects connecting the STR to the Constellations. I didn’t want to write about the Anthem STR myself -- I just wanted to hear it, and experiment with some of the features that Diego had described that had piqued my interest.

But in almost no time I grew so enamored of the STR’s sound quality and all those features that I knew I had to write about it, and give every audiophile out there another opportunity to be exposed to it.

First, Diego was right in saying, in his review, that the STR “offers an unprecedented level of flexibility in assigning inputs.” It has 12 physical inputs: four digital (USB, AES/EBU on XLR, and S/PDIF optical via TosLink and coax via RCA), and eight analog -- three each of single-ended (RCA) and balanced (XLR), and phono MM and MC (RCA). Any of the 12 can be renamed for display on the front panel, its gain adjusted through ±20dB, converted to digital if analog, etc. All of that is impressive enough, but the STR also lets you create up to 30 “virtual” inputs, each of which can be renamed, assigned in any number of ways to any physical input, and configured to your taste.

Anthem originally developed virtual inputs for their home-theater processors and receivers; if you’ve never used one of those models, the very idea might seem odd or even superfluous. But virtual inputs can be very useful in some systems, particularly if you use ARC Genesis. Let’s say you have a turntable with an MM cartridge connected to the STR’s MM phono input, whose default name is Phono MM (you can rename it anything you want). You can leave that input in the analog domain, so that it’s never converted to digital before being sent to your amplifier. But let’s also say that you want to have the option to use ARC Genesis to experience room-optimized sound from your turntable. You can create a virtual input assigned to the same physical input the turntable is connected to; name it, say, Phono MM2; configure your new virtual input to digitize the signal via the STR’s Convert Analog feature; and enable ARC Genesis for that input. That done, you can use the front-panel controls or the supplied remote control to switch between Phono MM and your new Phono MM2 input, depending on whether you want to hear the signal from your LPs as pure analog, or digitized and processed by ARC Genesis. That is essentially what Diego did when he wrote his article about the STR’s phono capabilities.

You can get more extreme: Say you have some records that, for proper playback, need to be equalized using a curve other than the standard RIAA curve required by almost all LPs made since 1954. The STR includes six additional curves, accessible via its digital-signal processer (DSP). So you can create another virtual input, also assignable to the physical input your turntable is connected to -- let’s call it Phono MM3 -- enable Convert Analog, then select the EQ curve you want Phono MM3 to apply. In terms of the STR preamp’s flexibility in handling its input sources, the limit is almost indistinguishable from the sky.

Although I’ve used a phono input above as an example, I haven’t yet used the STR’s phono stage. Instead, I’ve focused on other features, such as its DAC section, because I mostly listen to music from digital sources. The STR’s DAC section supports up to 32-bit/384kHz PCM and DSD128 via its USB input (its other digital inputs support PCM up to 24/192). It doesn’t support MQA. But if you’ve read some of my past articles about MQA, you’ll know that I don’t think that’s a deficiency -- I’ve never believed the MQA format to have technical merit or any real benefit for consumers, and still don’t.

The Anthem STR worked perfectly -- the Asus Zenbook UX303U laptop I use as a music server, running Windows 10, recognized the preamp the moment I connected them with an AmazonBasics USB link. Via Roon, I sent music files to the STR from a solid-state drive or streamed them from Tidal without a hitch.

Nor was the sound of the STR’s DAC section anything to complain about, as Diego also found. The sound I heard was always startlingly clean, remarkably detailed, and super-dynamic. In my opinion, the STR’s DAC can hold its own against standalone DACs costing several thousands of dollars -- if someone used it as only a DAC, they’d still be getting good value for $3999. But, of course, the STR has many other features, such as that MM/MC phono stage, as well as what many familiar with Anthem consider its star attraction: ARC Genesis.

Wikipedia.org defines digital room correction as “a process in the field of acoustics where digital filters designed to ameliorate unfavorable effects of a room’s acoustics are applied to the input of a sound reproduction system.” Essentially, it’s a digital system that attempts to correct the loudspeakers’ output for anomalies that occur when they interact with the room they’re being played in -- nasty reflections, and standing waves in the bass that can distort the sound, the latter showing up as peaks and nulls in the frequency response. A good room-correction system such as ARC Genesis can go a long way toward curing these problems.

To work at all, room correction requires that measurements be taken of the system’s sound in the room -- typically, taken by the user. For this, Anthem supplies with each STR preamp a calibrated microphone, with stand and cord. The ARC Genesis software, a free download from their website, runs on Windows and Apple computers. It generates the test tones, sends them through the system, records the room’s response, compares it to its built-in target curve, crunches all those data to produce the filters required to match the system’s output to the target curve, then uploads the new curve from the computer to the STR. All you supply is the computer.

ARC Genesis has two modes: Auto and Professional. Like Diego, I went straight to Professional, so I could make adjustments to ARC Genesis’s prescribed settings, but novices might be better off with Auto mode. According to writer Roger Kanno, who’s owned an STR preamp for over a year now, Auto gets you remarkably close to the best sound possible with very little effort, even if your speakers -- and one or two subwoofers, if you have them -- aren’t ideally positioned.

But I didn’t find Professional mode hard to use. Through onscreen graphics and clear, easy-to-follow instructions, the system tells the user how to position the mike for the five different measuring positions required. It took just a few minutes to do all the measurements; after processing the data, ARC showed me each speaker’s response, and the target curve it wanted to apply. I approved these results, and told my computer to upload the filters to the STR.

I suspect that if I’d used Auto, the initial target curve it showed me would have gone straight into the STR. But because I used Professional, ARC let me make changes to the target curve. All I did at that point was to reduce the upper limit for room correction to 200Hz from the default of 5000Hz. I wanted to hear what ARC Genesis would do only in the bass, where room correction matters most, before I heard whatever changes it might want to make up through the midrange. After I’d done extensive listening with a wide variety of music, the bass in my room sounded much more controlled with ARC enabled than with it not enabled.

ARC Genesis includes another incredibly useful feature that no other room-correction software I know of has: bass management for one or two subwoofers. This feature works in concert with the single-ended (RCA) and balanced (XLR) left- and right-channel subwoofer outputs on the STR’s rear panel -- connections seldom found on preamps. Because I don’t use a sub, let alone two, I couldn’t try this feature, but I was able to look at all of ARC Genesis’s subwoofer-management options. From what I could tell, the STR has everything you need to integrate a sub(s) into your system and room: the requisite low- and high-pass filters, level adjustments, and a new feature that optimizes the phase relationships between the two main speakers and the sub(s). I plan to test ARC Genesis’s bass management in a sat-sub system I’m setting up.

For his review, Diego used the STR with his Focal Sopra No1 stand-mounted speakers and two SVS SB-4000 subwoofers. He wrote that the resulting sound, with only the STR managing his subwoofers, was the equivalent of what he uses for bass management already: a complex setup comprising a miniDSP DDRC-22D processor running Dirac’s Live 2.0 room-correction software, miniDSP’s UMIK-1 mike, a McIntosh Laboratory C47 preamplifier, the internal crossovers of his SVS subs, and a Marchand Electronics external crossover built to his own specifications. That the STR with ARC Genesis effectively replaced all of that gear with a turnkey solution should not be overlooked by anyone looking to use one or more subwoofers.

I wanted to test some other things I might not have known about had Diego not written about them in his review. One was the STR’s self-noise. Diego had found that the STR’s analog inputs were commendably quiet when the signal remained in the analog domain -- but with Convert Analog enabled, or any of the digital inputs selected, he could hear hiss when sitting in his listening chair with the volume control at its maximum setting (+7.5dB) and no music playing.

I selected an analog input without Convert Analog enabled, and turned the volume all the way up, with no music playing. Like Diego, I found the STR quiet -- I could hear a little bit of hiss only when I put my ear within inches of a tweeter, which is normal. But when I selected a digital input, the hiss increased to the point that I could hear it about 4’ from the speaker. Diego was right -- the STR is noisier with its digital circuitry engaged. I then set the volume to a level typical of what I’d listen at, -35dB, which lowered the hiss to a much more acceptable level -- to hear it, my ear had to be within about a foot of a tweeter.

Bottom Line: The STR was not the quietest preamp I’ve had here -- for that, the Simaudio Moon 740P and the EMM Labs Pre pure-analog preamps, which respectively cost more than two and six times the STR’s price, get top marks -- but it’s reasonably quiet. For me, the hiss was a nonissue.

Another criticism Diego had of the STR: He found its volume knob a bit shallow and slippery for a one-finger turn -- as he said, “a very minor quibble.” However, I liked the knob’s shallowness -- to me, it’s more attractive than if it protruded farther from the surface of the faceplate. And while the control itself is indeed very smooth, that never bothered me when I used it -- I could always grip it, even with one finger.

The only real complaint I had about the STR was something Diego didn’t mention. Although ARC Genesis is fairly easy to use on a computer, the menu of the STR’s own onscreen display (OSD) can be a bit of a bear to navigate. This has mostly to do with the STR having so many features and customization options that it’s easy to forget where a particular one is. But I’d rather put up with a little of this frustration than lose some of the very options and features that go a long way toward making this preamp so desirable in the first place.

After several weeks with the STR preamplifier, I’m fully on board with the conclusion of Diego’s review: “What Anthem has created is extraordinary for the price.” In fact, I’d go further -- I think the STR can be considered extraordinary regardless of its price. It’s not only rich in features, some of which it shares with no other two-channel high-end preamp. Particularly for the room-correcting, subwoofer-using audiophile, the implementation and integration of those functions -- not only with each other but with everything else the STR does -- are so elegantly and thoroughly thought through that the result is a dream machine for any audiophile who wants to marry a pair of main speakers to one or more subs. Roger Kanno is one of those audiophiles, and now I know why he bought an STR the moment it came out. Were I in his shoes, I’d buy one, too.

Anthem’s STR preamplifier is one of the most forward-thinking audiophile products on the market today. I’m confident it will still be relevant many tomorrows from now.

. . . Doug Schneider
das@soundstagenetwork.com