November 1, 2009

Behold APU768 Preamplifier-Processor-DAC

Category: Electronics


The precursor to the Behold APU768 could well be thought of as the Audio Suite modular preamplifier, introduced in 1985 by Cello, now defunct. You could configure the Audio Suite with a phono input, various line-level inputs, and balanced and/or unbalanced outputs, and it had a separate power supply. In terms of functionality options it was a product ahead of its time, and used units still seem to command higher-than-average prices when they show up on eBay. The Audio Suite was also outrageously expensive for the era in which it was introduced, costing well into five figures, depending on which options were included -- back in the early 1980s, not much of anything in the high end was as costly as the Suite. But those who owned an Audio Suite swore that the flexibility it offered and the quality of sound it produced were worth the exalted price. Some still feel that way about it today.

The Behold APU768 shares many similarities with the Cello Audio Suite, at least in terms of being modular, offering many different functions depending on its configuration, and being expensive when considered against almost everything else it competes with ($58,000 USD as configured for the review). Like the Audio Suite, it is also well ahead of its time; if my experience with it proves any indication, the Behold, too, might be considered a classic 20 years after its launch. But the question I asked myself was whether the APU768 is the harbinger of preamplifiers to come. Perhaps the answer is yes, but other electronics manufacturers will have to climb a steep learning curve before being able to produce such a technically advanced component.

A 2009 version of the Cello Audio Suite? Let’s explore it.

Modular design, advanced functionality

Behold is a German firm that produces a line of electronics -- power amps, a DAC, a CD player, an integrated amp, etc. -- that is quite innovative in terms of technical capability. Chief designer Ralf Ballmann, an extremely opinionated engineer, has some very pointed ideas about how an audio system should be designed and implemented. Ballmann did not start his engineering career in high-end audio, but began by designing network analyzers. He found a home in our field when he realized that his training could help him innovate in what he considers some critical technical areas of high-end audio.

Before beginning the design process for his Behold electronics, Ballmann examined several of the leading electronics products that were available, and wasn’t impressed by what he saw and heard -- he knew he could do better. What he came up with was way outside the box. For instance, in a full Behold system (sans loudspeakers and speaker cables), the digital-to-analog conversion is performed not in the source component, or even in the processing unit or separate DAC, but in the power amplifier -- the last stage before the signal is amplified and sent on to the speakers. Ballmann contends that the signal should be kept digital for as long as possible. The APU768 reviewed here was auditioned in The World’s Best Audio System 2009, in this type of system model. I also used it in my reference audio system, where it performed D/A conversion.

Each APU768 ($30,000 base price) is configured and built to order with any number of optional modules that will equip it for any number of functions. A single APU768 can accommodate 14 of these modules, mixed and matched in virtually any configuration; the unit I reviewed was assembled for stereo operation, but the APU768 can also be configured to anchor a multichannel audio system. Some of the more obvious choices of modules were included in my unit: the ODI768 ($3500) module, with eight digital inputs, four S/PDIF on RCA jacks, and four TosLink; the ADC192 ($5000), with four analog stereo inputs (these can also be configured as multichannel inputs), contains an A/D converter (all analog signals are converted to digital; there is no analog pass-through); the DIO768, with three digital inputs and three digital outputs; the DAC192 ($4500), with an internal D/A converter and the requisite stereo analog outputs on RCA and XLR jacks (multiples of these modules can be used for multichannel operation); and the APD192 ($15,000), which includes Ascendo-derived room-correction software (see below).

The rear of the APU768 is built on a card-and-slot architecture: essentially, you remove the top panel of the unit, carefully insert each module into the digital bus system, replace the top panel, and secure the module to the unit by screwing its aluminum-plate rear housing to the frame of the APU768. If you order an APU768, it will of course come already fully loaded and configured for you. But if your needs change over time, modules can be shipped to your dealer and this process can be completed in the field.

The physical construction and layout of the APU768 are as impressive as high-end audio gets. The all-aluminum chassis feels like a brick when lifted, and the rather sparsely populated faceplate belies the sophistication lurking behind it. The largest rotary control, at the right side of the faceplate, allows the user to turn the APU768 on and off by shallowly depressing the knob. This knob also controls the volume. The knob at the left end of the faceplate allows the user to navigate, select, and activate items in the extensive menu system. A large LCD screen displays the menu system, volume readout, and input selection, is easily read from across the room, and can be customized to display varying levels of information to suit the user’s needs. Immediately to the right of the display is the third knob, which can be used to control other Behold components, such as their CD player. The APU768’s small, rectangular, external power supply can be located away from the main unit and connects to it with a twist-lock-terminated power cord. The supply can then be connected to the wall with your own power cord via the IEC input jack.

The Behold’s room-correction system is quite advanced, and its setup and use are more complex and encompassing than any I’ve seen. The software itself was developed by Jürgen Scheuring of Germany’s Ascendo, manufacturers of some highly regarded loudspeaker systems. Partially funded by a government grant to study room acoustics, Ascendo has developed a room-correction system that uses advanced programming and a professional-style user interface to accomplish its mission. When you order an APU768, the dealer will come to your house with a laptop fitted with Ascendo’s Room Tools software, which interfaces with the APU768. A microphone then connects to the laptop, and the computer is connected to the APU768 via an Ethernet cable. With the microphone in the listening position, a series of measurements is then taken, using built-in test tones. Readouts on the laptop’s screen show the left- and right-channel frequency responses.

Other measurements are also available, and these will be used in the setup as well; my description here is greatly simplified to give you just a feel for how it all works; detailing everything the system will do requires a manual unto itself. In a nutshell, the room-correction system can be used in two ways: It can address nonlinearities in your system’s frequency response through its automatic-correction function, and with it you can create custom frequency-response curves to suit your listening tastes, room, and speakers. The included remote control lets you scroll through four saved FR curves and turn the correction software on and off, so that you can easily do A/B comparisons on the fly to hear what effect the software is having.

The corrected frequency response in my Music Vault listening room with the Rockport Technologies Arrakis loudspeakers.

Sound and use

Because of the varying nature of a modular component, the Behold APU768’s sound will entirely depend on how it is configured and in what system context it’s used. It can be used as a simple preamplifier, albeit with A/D and D/A stages, but that is the least likely use for such a multidimensional product. Far more logical, in what I would figure would be the simplest system it would be used in, is to use an APU768 as a preamplifier and DAC, which is what I did through much of the review period. I also added the Ascendo room-correction feature, and I’ll note how that performed as well. I didn’t cross over my speakers using the active crossover functionality, which would have required multiple power amplifiers and a speaker system specifically set up for active drive.

I fed the APU768 only digital signals, mainly S/PDIF from my Apple MacBook laptop. I don’t know how transparent the ADC section is because my unit didn’t include that module. Most audiophiles consider it anathema to convert to digital a pristine analog signal from a phono or CD source or a computer-served DAC, only to then reconvert that signal to analog. But after giving this a lot of thought, I’ve realized that a case can be made for it, at least in one situation: where the user has some severe room-related frequency-response problems that can be solved only with electronic correction. I’ve long been of the opinion that tonal balance is very important to how we perceive sound quality, and that the most pronounced differences heard among high-end audio systems can be accounted for by deviations from flat frequency response. Most speakers don’t measure all that flat in an anechoic chamber, and things get only worse when they’re placed in actual listening rooms; in most cases, there will be significant shifts in tonality due simply to the room-loudspeaker interface. Nonlinear bass is one of the worst offenders, but depressions and otherwise ragged behavior throughout the audioband can be enough to make even really good components sound horrible.

I found the Ascendo-derived room-correction system a marvel. The APU768 provided some mild equalization that brought down a slight emphasis in the midband, smoothed some peakiness in the bass, and partially filled in one depression I had at around 80Hz. The overall sound, with equalization courtesy the APU768, was now fuller in the lower registers and more neutral in the midrange, bringing male voices, for instance, in line with what I heard higher in the audioband. Neil Young’s Live at Massey Hall 1971 (CD, Reprise/WEA 43328) was rendered with Young’s voice displaying just the right amount of presence but without sounding too forward. His guitar was crisp and clean -- I heard no hint of electronic haze or grit.

I put one listener through a quick A/B test, with and without room correction. He preferred the sound without room correction, stating that he heard a slightly compressed soundstage with it on. I felt that the soundstage wasn’t really compressed, but that the tonal balance of the system was on a more even keel, with no individual elements jumping out at me. We might actually have been hearing approximately or exactly the same things, while bringing to the experience our different tastes in sound.

There was no question that the bass range was extremely linear with the room-correction software employed. Acoustically, the Music Vault is a fairly neutral environment. But as in any room, there are dimension-related bass modes -- peaks and dips in the frequency response -- that must be addressed acoustically or electronically. The APU768 was able to improve areas that I’ve been unable to address with passive bass traps -- the traps designed to absorb frequencies under 80Hz or so are way too large for the Vault. More linear bass, coupled with the bass articulation and power of which the Rockport Arrakis loudspeakers are capable, yielded the best bass I’ve yet heard in my room. Bass instruments were as nimble as ballerinas when they needed to be, yet were utterly controlled with massive power when that was called for. Room-related artifacts ceased to be problems, leaving only clean and articulate yet deep and powerful bass.

One example was the drums from one of my reference bass tracks, "Norbu," from Bruno Coulais’s music for the film Himalaya (CD, Virgin France 848478). This is an instance where the room can quickly overwhelm the sound produced by the speakers. When the massive drums are struck, the bass energy is sustained, deep, and powerful. The room can resonate wildly, swamping the output from the speakers and obscuring details within the music. With the room correction off, the subtle trailing decay as each thwack rolled into the next sounded somewhat one-note-like, the room ambience in the recording hidden by the bloat in my room. With the bass response more linear, I could hear farther into the recording space, and more minute details within a larger soundstage. This greatly affected my enjoyment of this track: Instead of sitting there wondering how much my room was influencing what I was hearing, I was confident I was hearing only the instrument and the space of the recording venue, and that heightened my sense of musical involvement.

As an example of just how real my system sounded with the APU768 at the helm, I recall a day in February, when fellow writer Randall Smith and I were setting up The World’s Best Audio System 2009. My wife was downstairs in our living room when she heard the system come on. We were playing Neil Young’s "Helpless," from his Live at Massey Hall 1971. It begins with only Young’s guitar, and Andrea bolted upstairs to see what was happening -- such was the transparency, tonal correctness, and overall real nature of what was being played that she thought one of us was actually playing a guitar in the Music Vault. She was amazed to find that it was TWBAS 2009 playing back that guitar, and said that she’d never before heard anything as real-sounding coming out of the Vault: "As real as I’ve ever heard from a stereo," she called it. It was an astute observation, quickly and honestly arrived at. I would eventually come to the same conclusion, but being an audiophile, it took me a little longer. Imagine that.

As a pure preamp-DAC, the APU768 was as transparent as any combination of products I’ve ever used. I could go down the list of preamplifiers and sources I’ve used in the past and how it compared with each, but I’ve not used any combination of them that was better than the Behold. It was, essentially, dead neutral.

That poses a conundrum for someone in my position. I get e-mail -- lots of it. More often than not, these e-mails are from readers who want buying advice about particular components that I have some experience with. When considering my answer, I often think, Would I buy it if I were this person? I let my answer guide my response. In the case of the APU768, formulating responses to such questions will take a bit more consideration. In my case, I couldn’t buy the APU768 because it would complicate my life as a reviewer. I need to be able to switch among separates -- DACs, preamps, room-correction devices, etc. -- so that I can evaluate them individually. The APU768 would take away that flexibility and make it impossible for me to do my job. However, if I were not a reviewer, the APU768 would simplify things completely, and give me state-of-the-art performance in all three of those product genres. I’m not going to insult anyone’s intelligence and talk about saving money on interconnects by having an all-in-one component like the APU768, which costs $58,000 -- those in a position to purchase the APU768 aren’t concerned with pinching pennies! But the reality is what it is: Performance-wise, the APU stands up -- and then some -- to its exalted price. It’s world-class as a preamp and as a DAC, and when you add its other features, it is the sole occupant of its category.


The Behold APU768 is a rarity: a unique component in a high-end marketplace that has far more me-too products than most journalists care to admit. It doesn’t use an off-the-shelf software platform from another maker, and there aren’t really any less-expensive alternatives that offer exactly what it will give you. Although you could easily think of the APU768 as a preamplifier that combines DAC and room-correction functionality (and an active crossover, and a multichannel controller, and . . .), the whole is far more valuable than simply adding up the number of boxes it could replace in your listening room. Add to that its vault-like construction, and you’re faced with a machine that is uniquely configured and built.

All that would be for naught if the APU768 didn’t sound like a million bucks -- or at least like $58,000. I can’t put an exact price tag on it -- if I said it sounded like $57,000, would that mean it had failed? But I can confidently state that the APU768 should be considered a first stop for those lucky few who can afford to assemble a state-of-the-art audio system. It can work wonders, and it won’t be outclassed by any other single component in the equation. The Behold APU768 is the most advanced piece of high-end electronics I’ve ever used.

. . . Jeff Fritz

Model: Behold APU768 Preamplifier-Processor-DAC
Price: $58,000 USD as configured ($30,000 base price).
Warranty: Five years parts and labor.

Theaterplatz 14
D-91054 Erlangen, Germany
Phone +49 9131-503700


US distributor:
Laufer Teknik
27 Whitehall Street, 3rd Floor
New York, NY 10004
Phone: (212) 269-6384



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