Marantz’s AV8802A preamplifier-processor : Music in the Round #76

As far as I’m concerned, an accessory is something without which your system would still work just fine. By definition, accessories are preferential, not essential: You buy them in the hope that they’ll improve the sound of your system, or make it easier or more convenient to use.

In my last column, in the November 2015 issue, I talked about Marantz’s AV8802A preamplifier-processor and two accessories: UpTone Audio’s USB Regen, and a DIY battery supply for my DAC. This month’s column is all about accessories, and for me that’s unusual. Some items, like interconnects and speaker cables, are usually considered accessories because they’re not fundamental components (eg, source, amplifier, speaker), even though they’re essential to getting any sound at all.

I could also wrestle with the electromagnetics of transformers and motors. At the time, digital signal processes were still mostly theoretical.Back in analog days, I could decide whether a different tonearm counterweight was a good idea because my undergraduate study of physics had covered the mechanics of mass, compliance, and frequency.

Today, I’m losing ground. While I grasp more than a bit of how music is digitally encoded and decoded, I find it difficult to understand how different data-transmission methods (USB, HDMI, Ethernet, FireWire, etc.) affect the quality of the analog output signal and, ultimately, listening enjoyment.

Consider such products as the AudioQuest JitterBug and UpTone’s USB Regen. Many people, whether skilled or naãve, biased or impartial, have attempted to test such gadgets, but I’m not aware of anyone who has demonstrated a link between variables in data transmission—beyond basic hardware specs—and what we can actually hear. Of the correlations we do see between hardware/software variables and the condition of a product’s output signal—measurements that can reveal either improvements or deteriorations in signal quality—most changes are so slight as to be considered below the level of audibility, amounting no change at all. (Of course, in all such cases, one can question whether relevant parameters were being tested.)

On the other hand, some manufacturers offer products accompanied by a technical description and a statement of goals for that product—but without test-bench specs. “Try it!” they say, and offer return privileges. Hope and expectation play big roles in deciding whether to add an audio accessory, choosing the particular one(s), and determining whether they’re worth the cost and bother. Expectation bias is a friend to such vendors, regardless of whether the product makes an essential difference or is a placebo.

Is there hope? I think so. First, several websites are hosting ongoing, apparently candid, and often contentious public discussions of the testing and measuring of data-transmission accessories. When the smoke clears, this give-and-take can have led only to better understanding of these technologies. Limited by my technical competence, I am a fly on the wall, but it’s fun to watch the sparks fly.

As for the “Try it!” approach, that works, too. Most of us have a closet stuffed with old accessories that didn’t stand the test of time. I’ve bought many gadgets, hoping they would improve the sound of my system by at least one audible increment, but most I’ve tossed aside. Some made no difference from the get-go. Others offered an initial flush of excitement, but the effect faded over the ensuing months. Few accessories have lasted long in my system: As audio technology advances, the worthwhile improvements effected by today’s accessories are sometimes incorporated into tomorrow’s new primary components.

These days, I might try an accessory because of word-of-mouth, so long as it doesn’t cost the sky. Despite my general skepticism of tweaks and accessories, I’m as much subject to expectation bias as the next guy. I’ll just tell you what I hear; as for the rest, I’ll wait for the dust to settle.

AudioQuest JitterBug USB filter
John Atkinson and the crew at (footnote 1) have already scrutinized this little gadget ($49), and everyone seems to like it. How could I not give it a try? I was particularly interested in using it in my weekend system in Connecticut, in which resides my already overachieving miniDSP U-DAC8 multichannel USB DAC: Getting eight channels of USB D/A for $299 is amazing—and budget-priced products always seem ripe for tweaking. And, as I reported last time, UpTone’s USB Regen—a USB signal regenerator intended to isolate audio peripherals from computer-system noise—had made a hugely satisfying improvement in that system’s sound: Surely, the miniDSP would be a suitable mate for the bruited ‘Bug.

When I asked AudioQuest for one, they sent two: AQ recommends using two—and no more—JitterBugs on each USB bus. I searched the JitterBug’s box, and AQ’s detailed instructions about how to use JitterBugs with various USB-connected devices, for any information about precisely what it does, and how. I found only two relevant statements:

“JitterBug is designed to remove unwanted noise currents and parasitic resonances from both the data (communication) and Vbus (power) lines of USB ports. . . .

“JitterBug’s dual-circuitry measurably reduces unwanted noise currents and parasitic resonances. It also reduces jitter and packet errors (in some cases, packet errors are completely eliminated).”

Well, that’s admirable—but how? JA was unable to find, in his measurements, any difference in DAC output resulting from the insertion of a JitterBug. Others have reported the same—but some have seen a change in the digital signal’s “eye pattern,” as observed on a digital oscilloscope. An eye pattern is a way of representing the precision of the digital pulses, which ideally should be square, thus indicating that the on-off transition is perfectly defined in time. Apparently, the JitterBug applies some kind of filter so that the squarewaves’ risetime is slightly increased—the opposite of what we want if we want to reduce jitter. However, while we assume this is not good in the digital domain, it’s unclear what effect such a filter might have on the DAC’s analog output. Is it possible that the JitterBug is actually doing something else, and that the apparent digital compromise is merely a side effect? As long as it’s reasonably square, is the eye pattern even relevant?

I don’t know. But I, like others, can hear the JitterBug’s positive effects on the analog output. I connected one ‘Bug between the output of my server and the input of the miniDSP U-DAC8, and—with or without the UpTone USB Regen connected—the JitterBug did seem to sweeten the treble. And when I removed the JitterBug, I missed it. Though the JitterBug’s effects were more noticeable without the USB Regen in the system, they were smaller than those of the UpTone accessory—which not only sweetened the treble but also, with multichannel recordings, tightened up the integration of elements within the soundstage.

Footnote 1: See the reviews by Michael Lavorgna and Steven Plaskin, respectively, here and here.

I tried inserting a second JitterBug, as AQ recommends, in a different USB jack on the same server, but heard no difference. I also tried the JitterBug in my other system, in Manhattan, with the exaSound e28 DAC. The effect was similar: subtle but sweet.

The $49 AudioQuest JitterBug is the archetypal accessory whose audible benefits are unsupported by measurements—and, for that very reason, some consumers will reject it out of hand: two imponderables, both of which bother me. At the end of the day, I can only recommend you try it and decide for yourself.

SOtM Audio tX-USBhubIn USB hub and sCLK-12.0 SuperClock digital clock
I had started down a slippery slope. Having been impressed with the effect on the U-DAC8’s performance made by UpTone’s USB Regen, I had to wonder if the Regen, or something like it, might have a salubrious effect on the sound of my exaSound e28 DAC. The e28’s designer, George Klissarov, had deterred me from adding a PCIe-standard USB output board to my Baetis XR3 server, characterizing it as unnecessary. Conversely, the designer of the Baetis, John Mingo, recommended just such a thing, even as he has focused his efforts on S/PDIF output performance.

The apparent success of the USB Regen has been followed by the appearance of other devices incorporating a USB repeater to preserve the integrity of the signal reaching the DAC, to ensure that it is perfectly timed and shaped. But how to choose? I dislike having lots of little boxes and additional cables attached to my system; as luck would have it, SOtM Audio recently announced their tX-USBhubIn USB hub board ($350), which can be mounted in an available slot in a PC, and can run on the computer’s internal power or an external supply. (For $370, SOtM offers a comparable external device, the tX-USBhubEx.) The tX-USBhubIn has two USB ports, each of which can supply +5V on USB or not. Given SOtM’s success with their servers and power supplies, and with their original tX-USBexp PCIe USB Audio Card, I figured that the tX-USBhubIn would suit my needs. SOtM describes the tX-USBhubIn as an “Audio USB 2.0 Hub” with “Ultra Low Noise Regulator,” “Ultra Low Jitter Clock,” and “Active Noise Canceller,” and makes the familiar request: “Do try and in person experience the high quality sound system produced from the new platform beyond and above the existing PC product criteria.”

To my surprise, SOtM also sent their new high-precision clock, the sCLK-12.0 SuperClock ($500), to further enhance the quality of the USB output. The sCLK-12.0 SuperClock—so new that it has not yet appeared on SOtM’s website as I write this—has impressive specs. SOtM’s sCLK-series clocks support their dX-USB HD, iM-USB HD, tX-USBexp, tX-USBhub, and other boards. Absent any official documentation, I was sent jitter-spectrum recordings made at the AES/EBU output of a dX-USB HD by a Stanford Research Systems SR1 audio analyzer with a bandwidth of 100kHz, zoomed to focus on the audioband. While all of the graphs were pretty flat, showing jitter levels mostly about 1ps on the log scale, the insertion of the sCLK-12.0 clearly removed a 10ps peak just below 2.5kHz (fig.1 & 2). The clock is evidently doing something, but again, the audible impact is undetermined.

Being a USB repeater, the tX-USBhubIn is to be connected to the main USB header on the mother board. It looks smaller and simpler than the tX-USBexp PCIe USB Audio Card, which occupies a PCIe slot and, essentially, establishes a separate USB bus. Both the tX-USBhubIn and the sCLK-12.0 SuperClock require power from the computer’s SATA interface; to make this easy, I spent less than $10 on an internal SATA power Y-cable. Installation took less than 15 minutes, with another 15 minutes to reassemble and reconnect the Baetis server, which then booted up just fine.

My first decision was whether to enable the 5V output on the USB port. Because the exaSound e28 is powered by its own battery, I hoped that disabling the 5V output would eliminate a potential source of noise. However, the e28 needs the 5V connection in order to be recognized by its driver. Enabled for 5V, everything functioned as before, and I was left with the music.

Switching from the XR3’s stock USB connector, the SOtM hub and clock made an easily audible improvement in the sound of a system that I’d already thought sounded entirely satisfying. Although measuring the sound levels before and after produced identical results, my immediate impression was that the music was now louder and clearer—an impression gained because I could now hear subtle distinctions in the midrange with much greater ease. The bass and treble were not obviously affected, except to the extent that some older, splashier recordings, such as Arthur Lyman’s 1958 release Taboo (CD, Rykodisc 417), were less disturbing. But good modern recordings, such as “Tin Tin Deo” (1996), from Oscar Peterson Meets Roy Hargrove and Ralph Moore (CD, Telarc CD-83399), lost none of their detail. In fact, stereo recordings sounded as good as via the Baetis’s own dedicated S/PDIF connection. To see if I might gild the lily, I inserted a JitterBug into the SOtM port, but to no avail. It did nothing, good or bad.

With multichannel recordings of complex orchestral music, such as Jordi Savall’s of Biber’s Missa Salisburgensis, with Hespärion XXI (SACD/CD, Alia Vox AVSA9912), I could have my cake and eat it, too. The Biber was recorded in a large, reverberant space, and I was immediately immersed in its ambience—yet individual voices had presence, and the entire ensemble was cohesive. Through the standard USB connection, the distinction between direct and reflected sound was confused; switching to the SOtM connection was like having the optometrist find the just right corrective lens: Everything snapped into place.

All of this comes at a cost. The list price of the tX-USBhubIn is $350, and the sCLK-12.0 SuperClock costs $500 (footnote 2). You might want to start with just the SOtM tX-USBhubIn, and see if it whets your appetite for more. I swallowed both whole and found them very satisfying.

JL Audio Fathom f113v2 powered subwoofer
Are subwoofers accessories? I think so. They’re important to home-theater fans, but many audiophiles loyal to two-channel stereo refuse to consider them, even when their preferred speakers are quite limited in bass power and extension. Perhaps bass isn’t all that important to them, or perhaps they’re daunted by the complexity of properly setting up a sub. I lived for years without a sub in my main system, in Manhattan. My Connecticut system included subs because I sometimes use it to watch movies—but with my NYC rig including three Bowers & Wilkins 802 Diamonds and a pair of 804 Diamonds, I did not lack for bass.

Or so I thought until late 2006, when I reviewed the predecessor of JL Audio’s Fathom f113v2, the Fathom f113 (which I’ll now call the v1). The v1 didn’t so much give me more bass as better bass. I was sort of pleased with Automatic Room Optimization (ARO), its one-band auto-equalization software, which handily dealt with a 50Hz room mode. But, over time, I came to rely on outboard EQ in the form of DSPeaker’s Anti-Mode 2.0 digital room equalizer or Dirac Live. Apparently, my room needed more help than any single-band filter can supply.

Enter the Fathom f113v2 ($4500), with Digital Automatic Room Optimization (DARO)! Aside from its new EQ software, the f113v2 is almost identical to the v1, with some subtle changes in the I/O panel on the back and the controls across the top front. Under its hood, the v2 boasts 3000W RMS short term, compared to the v1’s puny 2500W, and its single, front-firing, 13.5″ driver has a modified suspension for greater linearity and lower distortion. In addition, the v1’s circuitry has been reconfigured so that no audio signal is routed through the v2’s control panel, and all small-signal circuits are contained in a cast-aluminum housing attached to the rigid rear-panel heatsink. Finally, because EQ is now accomplished by DARO, digital-signal processing (DSP) has supplanted many analog components, presumably leading to improved unit-to-unit matching and product reliability.

DARO differs from ARO in several ways. Instead of a single filter, it has 18 bands of cut-only correction, with automatic output-level realignment post-EQ. Each band is adjusted independently by the DSP. In addition, microphone gain and output levels are adjusted automatically, without user effort, which results in greater ease of use and, more important, more accurate and consistent results.

I placed the v2 in the same spot just vacated by the v1, measured its response, then ran DARO. Because ARO and DARO address only peaks, that position for the sub was chosen to minimize, as much as possible, troughs in the frequency response. (True nulls are bottomless pits, and are thus uncorrectable.) DARO was easier to operate than ARO, especially for anyone who’s used the latter. You simply set the provided calibration microphone at the listening position, push a button, and get out of the way. Band-limited pink-noise pulses are pumped through sub and room for a couple of minutes. That’s it!

The measured and audible results were much better than I could get with my v1, and all previously observed peaks were corrected. As before, the payoff was not more bass (although that was available on demand): The v2’s improvement over the v1 was the complete disappearance, from my conscious awareness, of the subwoofer’s existence. Switching from five full-range channels to five channels crossing over at 40Hz to the f113v2 produced greater clarity below 100Hz, as the main speakers were relieved of powering the bottom end (perhaps resulting in reduced Doppler distortion?), and the low bass was cleaner, due to the f113v2’s more advantageous position in the room and more efficient EQ. A win-win.

There was more. JLA’s Fathom subs can be daisy-chained, allowing DARO to handle as many as you can afford. If you have two f113v2s, the recommended arrangement is to run DARO on the first and set up the second sub as a slave. The first v2 will EQ the two subs’ combined output. In my situation, the second sub was a v1; I was advised by JL that “the gain structure for the slave paths is different between the V1 and V2. As such, run your V1 in Master mode with all signal processing defeated and adjust the Level control (in Variable gain mode) as needed to match the V2 master.” This worked flawlessly, but with most recordings, switching from one to two JLA subs made no audible difference to me.

I do understand that those who play different music (eg, techno), and/or who play it much louder than I do, might appreciate the additional power. When I could detect differences, they were most apparent with recordings made in highly reverberant spaces in which the venue’s modes are in the ultralow, nearly subsonic range. In stereo, it was the Cowboy Junkies’ familiar The Trinity Session (CD, RCA 8568-2-R). In multichannel, try the Berlin Brass’s disc of music by Gabrieli: Berliner Dom: Music for Brass & Organ (SACD/CD, Pentatone PTC 5186509), and that spectacular recording of Biber’s Missa Salisburgensis. With these, I was embraced by the sense of place even before the music began, and remained engaged more deeply because of it.

The verdict is easy. JL Audio’s Fathom f113v2 is everything good from the Fathom f113 and more. DARO is a huge and needed improvement, and the backward-compatibility with the v1 is appreciated. In 2006, I hadn’t thought I needed a subwoofer—and certainly not two. Now, it’s hard to imagine listening without at least one Fathom f113v2. This is one accessory that does realize its potential to improve my system.

Next Time in the Round
I look forward to reporting on a new network-based product from Merging Technologies, the NADAC Multichannel-8; and, from exaSound, the PlayPoint Network Audio Player. Better get your Ethernet tuned up.

Footnote 2: At the time of writing, the US distributor offered a special introductory price for the tX-USBhubIn, and promised a similar special price for the as-yet-unlisted sCLK-12.0 SuperClock.