different possible signal paths through the processor (some simple and short, other complex and long). The good news can be stated in a nutshell. Even through its longest, most complex internal path, the Arcam AV8 preserves the quality of the input audio signal better than most competing processors do, even through their shortest, simplest paths. That's a stunning sonic achievement. It's a testament to the work that the Arcam engineers have put into getting the best possible sound out of the same IC chipsets that other high end processors employ, and into reducing the adverse influence of the hostile environment inside an AV processor's chassis.
To prove this finding, we directly compared the sound of the Arcam AV8, feeding the signal through its longest and most complex internal path (even involving extra A/D and D/A conversion steps), to the sound of competing high end processors 1 and 2, feeding the signal merely through their simplest and shortest path (an analog volume control and line section buffer stage). The AV8 still won! The AV8 still revealed more information from the recording, and portrayed better spatial imaging, even though it was handicapped with both hands tied behind its back. Amazing!
We're now going to explore the many ways of using the AV8, and the relative sonic merits of each. Our goal is to teach you how to get the very best sound out of this remarkable unit. Keep in mind though, as we explore the sonic merits of these various signal paths, that we are really comparing strength to strength. Some signal modes and some signal paths are stronger than others, but all are strong, since even the weakest of them, even the longest and most complex path, still is stronger and sounds better than competing AV processors in their best sounding, simplest path.
An audio component like the AV8, that is so superbly revealing of the input audio signal, will naturally also be very revealing of itself, and of the sonic differences between various signal paths and modes. That's especially true if the input signal is of extremely high quality, as it was indeed from the DV27A. Thus, even though all modes and paths through the AV8 are sonically strong, and far stronger than other competing processors, we nevertheless expected to hear the AV8 revealing which of its modes and paths were the very best sonically.
AV8 Analog Direct Throughput
As expected, the AV8's best sounding path is its direct throughput mode, which inputs an analog audio signal and puts it through only the analog volume control and output buffer stage, thereby bypassing all signal processing, and using the AV8 as merely an analog audio preamp line section. The AV8's direct throughput mode sounds slightly superior to all its various processing modes, in the classic audio virtues of transparency, resolution, and clean purity. And it's a pretty close second to the stunning audio quality produced by the DV27A itself, as we heard above by plugging the DV27A directly into a power amplifier.
The AV8's analog direct bypass mode produces excellent sound that is very enjoyable heard on its own terms. Only by hypercritical direct comparison with the stunning intrinsic sound of the DV27A itself could we hear some slight information losses, which of course you must expect to find in every real world preamp line section, since none is perfect. Specifically, the AV8 analog line section imposes a slight solid state glazing over of subtle audio details in the upper frequencies, so that they are not quite as airy and individualized as they are coming out of the DV27A. The AV8 analog line section also adds a slight crispness in the lower treble, similar to what we heard in the DV27A. And of course there's a slight transparency loss, compared to the incredible transparency of the signal intrinsically put out by the DV27A.
Note that if we had employed a lesser quality source than that amazing DV27A, we probably would not have been able to detect any sonic losses at all in the AV8's direct throughput line section. Again, it is precisely because these Arcam units are so superb, at revealing sonic information from the disc, that they are also so ruthlessly revealing of subtle sonic differences in their own performance. The end result through the AV8 analog direct line section still sounds so good that you won't hear any sonic problems from the AV8. And the end result sounds literally worlds better than the equivalent preamp line sections of other competing AV processors we tried.
You can use the AV8's direct analog throughput mode for any analog input signal, be it two channel or multichannel. For two channel stereo analog inputs, you can optionally choose either to engage this direct mode of the AV8, or to engage the AV8's signal processing. On virtually all two channel stereo material, we found that we preferred not to opt for the direct mode alone, because the AV8's signal processing does such an incredible job of extracting surround ambience information from two channel recordings, and building an amazingly believable surround space. So we prefer to employ the AV8's signal processing for virtually all two channel sources, using signal paths to be discussed below.
Then, for multichannel analog inputs (such as the incredible sounding analog signal put out by the DV27A for DVD-A, DTS 5.1, and Dolby Digital discs), the AV8 does not give you any choice, and the direct mode is mandatory (indeed, it is automatically selected by the AV8). In the noble pursuit of high end perfectionism, the Arcam AV8 even shuts off the power to all its digital signal processing circuitry, so that radiation from this digital circuitry does not contaminate the pure analog signal inside the same chassis box.
Interestingly, this purist handling of the multichannel analog inputs created a practical functional problem for us. Precisely because the Arcam units are such masters of space itself, we found that back surround loudspeakers are very important to creating a truly believable surround soundfield. But this back surround signal is not represented among the five (plus subwoofer) analog audio lines coming into the AV8 from the DV27A. Only the AV8 can extract or generate this back surround signal, and only via its signal processing sections. And these signal processing sections are not available to the signal path for multichannel analog inputs, such as from the DV27A (indeed, these signal processing sections even have their power turned off).
One workaround we employed was to feed the five analog output channels (plus subwoofer) of the DV27A directly into the power amplifier, and use a simultaneous digital line to the AV8 merely for the purpose of generating a back surround signal, with spectacular sonic results. Similarly, for EX or ES soundtracks with a back surround signal already matrix encoded into the side surround channels, we fed the three front analog output channels (plus subwoofer) of the DV27A directly into the power amplifier, while using the digital line to the AV8 to decode the EX or ES matrix and thereby extract the three surround channels.
We wish that there could be an option for using the AV8's direct throughput mode for multichannel analog audio, and simultaneously turning on and using the AV8's idle signal paths through the signal processing sections. Then, for example, we could connect the DV27A to the AV8 with a digital audio line as well as the multchannel analog audio lines. The analog audio lines could still follow the direct signal path through the AV8, while the digital input could be routed through the otherwise idle signal processing sections, just to extract or generate a back surround signal. This would allow us to hear Dolby Digital soundtracks at their sonic best and in full spatial surround glory. And it would also prove helpful to many DVD-As, which are often too closely miked and which therefore would be helped by enrichment of the surround space ambience, just as back surrounds can provide so well.
Note that we found back surrounds crucial for spatial believability on all types of recordings (even two channel stereo), not just on the few soundtracks with explicit EX/ES back surround signals already encoded, so the benefits of a dual simultaneous pathway through the AV8 would be widely applicable and enormously beneficial. Remember too that the DV27A includes on-board volume level and delay trims, so that its multichannel analog audio output can already include all the fine tuning needed to optimize portrayal of a realistic surround soundfield for the five channels it does put out, so these five channels can indeed be put directly through to the power amplifier without further signal processing.
Similarly, it would be helpful for playing DVD-As if the AV8's processing sections could optionally be set to tap into the two side surround analog inputs. In this way, the AV8's processing circuitry could generate a back surround signal from the two side surround signals, even when playing DVD-As. Note that the full content of all channels on a DVD-A cannot legally be sent over an unencrypted digital line, so the digital line from the DV27A to the AV8 does not carry all the information needed to derive a true back surround signal from (although an ersatz substitute back surround signal, derived from the partial signal that still does come over the digital line, might still be sonically effective in enriching ambient surround space).
AV8 Signal Processing Paths, Analog and Digital
We had expected the AV8's analog direct throughput mode to sound the best, and it did. But of course you cannot utilize the AV8's powerful and flexible signal processing capabilities in this mode, precisely because this direct analog mode bypasses all signal processing stages.
We found that we wanted to engage the AV8's signal processing for most program material, because the AV8 does such a wonderful job of extracting spatial information and sending it to the various loudspeakers, thereby re-creating that incredible spatial experience we described at the beginning. With multichannel program material like Dolby Digital DTS 5.1, and DVD-A, we could do this, and achieve sonic nirvana, by the purist tactic (mentioned above) of playing the DV27A multichannel analog output directly into a power amplifier and subwoofer, while simultaneously running a digital line to the AV8 in order to still make use of the AV8's signal processing, in this case merely to generate back surround signal information. On the other hand, with multichannel program material encoded in Pro Logic II, we have no choice but to run the entire signal in digital form from the DV27A to the AV8 (since the DV27A lacks these decoding capabilities that are included in the AV8, and since the AV8 offers analog inputs for only two channel material if one wants to route it through the AV8's signal processing).
Then, with two channel stereo program material, we had a choice of sending the signal into the AV8 via the digital line or via an analog line, from the DV27A or any source that offers both analog and digital outputs (obviously, if a source such as a stereo tuner offers only analog outputs, then one must send its signal into the analog input of the AV8 for signal processing). Which brought us to the next natural question: which path sounds best through the AV8, for two channel inputs?
If one wants to hear the two channel stereo source in its purest sonic form, Arcam has thoughtfully provided the wonderful sounding direct analog throughput mode as a selectable option for two channel analog inputs (the same option that is forced upon the AV8's multichannel analog inputs). But, if one wants to hear the benefits of the AV8's spatial enrichment prowess in extracting and portraying spatial surround ambience from two channel program material, then of course one will want to choose to go through the AV8's signal processing stages. We developed a workaround that gave us the best of both worlds, similar to that discussed above for multichannel program sources. Since the DV27A thoughtfully provides an extra set of analog output jacks for the front left and right channels, we simply routed these two channels directly to the power amplifier (using the DV27A's built in level controls as a volume control), thereby again gaining direct access to the incredible intrinsic sonics of the DV27A for the two main front stereo channels. Then we simultaneously fed the DV27A's output over the digital line to the AV8, and employed the AV8's signal processing to extract all the ambience information to feed to the front center channel and the side and back surround channels (plus subwoofer).
If one wants to feed a two channel stereo signal into and through the AV8's signal processing stages, which input mode sounds better, the analog or digital input? The digital input has the theoretical advantage. That's because the signal processing stages do their work in the digital domain (as they do in all modern signal processors). If one brings in the signal in digital format, then it stays in digital format all the way through the AV8, until just before the volume control and that analog output buffer stage, where a high quality DAC in the AV8 finally converts the audio signal to analog. Indeed, if the original program medium is digital, like a silver disc, then the audio signal stays in the digital domain all the way from the medium, and through all the AV8 signal processing, to very near the output of the AV8. With this digital input route, the DAC in the DV27A (for example) is not used, and the DAC in the AV8 is used instead.
In contrast, if one brings the two channel stereo signal from the DV27A into the AV8 in analog form, then the audio signal has to go through three conversions instead of just one. It has to be converted from digital to analog in the DV27A, then from analog to digital at the input of the AV8's signal processing stages (since all signal processing is accomplished in digital), and then back to analog again near the output of the AV8. Each such conversion theoretically takes a sonic toll on the signal, since conversions are necessarily (in the real world) approximations, so inserting three times as many such conversions in the signal path would naturally cause greater sonic degradation.
To compare all possibilities directly, we explicitly compared the sound of the AV8 for three different paths through the unit that a two channel stereo signal could follow. The best sounding route, in the classic audio virtues, was indeed (as expected) the direct analog throughput choice, which went only through the AV8's analog line section output stage.
The next best sounding route was to bring in the two stereo channels via the AV8's digital input, and send out all channels (including this time the two main front channels) from the AV8. Through this path, the AV8 signal still sounds very clean, with very clear, well defined outlines. Compared to its sound through the direct analog route (the signal source still being the DV27A), the AV8's digital route does evince a slight loss of transparency, sacrificing a little of the signal's subtle inner detail and three dimensional ambience. But this is understandable, given that this digitally input signal is now traveling all the way through the AV8's complex signal processing circuits (there is of course no such thing as an analog bypass for a digitally input signal). Indeed, Arcam is to be heartily congratulated for the high quality of sound they have achieved for this long and complex signal path, which again beats the pants off competing AV processors, even in their simplest, shortest path mode as a mere analog line stage. It's comforting for you to know that this digital input path, which accesses all signal processing capabilities, sounds so good in the AV8, because this is the most convenient way for you to connect the AV8 to the DV27A (or other digital output units), for listening to all program material except DVD-As. Since this digital input is the easy, convenient path that most of you will use, you can be confident that you'll be getting excellent sonics by using the AV8 this way.
Incidentally, this digital input path also sounds slightly brighter in tonal balance above 3 kHz than the analog paths through the AV8. That's because this digital input path now utilizes the AV8 as the sole D/A convertor in the system, substituting the DAC in the AV8 for the DAC in the DV27A - and Arcam has intentionally voiced the filtering and decoding algorithm of the AV8 DAC to be slightly brighter than the otherwise identical DAC chipset in the DV27A. Their belief is that film soundtracks sound better with a slightly brighter tonal balance, and the AV8 will be used primarily for listening to film soundtracks, whereas the DV27A's internal DAC will be used primarily for listening to music, which sounds better with a slightly less bright tonal balance. However, because the AV8's signal processing capabilities wreak such spatial portrayal magic on music recordings, including two channel stereo recordings, you will surely wind up using the AV8's digital input and in-house DAC for music as well as for film soundtracks, so you will be experiencing the slightly brighter tonal balance of the AV8's DAC on music too. Don't worry about this. We critically compared the brightness of the two DACs on music, and, while the AV8 DAC was indeed audibly brighter than that in the DV27A, both versions sounded very natural and realistic (the difference merely sounded like hearing live music from a different seat at a concert hall).
We found that the AV8 is very sensitive to and critical of the sonic quality of the digital interconnect cable you employ to bring in the digital signal from the DV27A. This cable sensitivity is normal for the highest end perfectionist D/A convertors, and once again is testimony to the AV8's superb ability to transparently reveal so much about the incoming signal. We obtained the best sonic results using Von Gaylord interconnect to bring the digital signal from the DV27A into the AV8. Some other high end cables we tried introduced a hard, information blocking glare, in the upper midrange or treble regions (so, if you hear this from the AV8, try changing your digital input cable).
The third path we evaluated was via the analog signal input, to and through the signal processing. This is the signal path that is longest and most complex, and that (from the DV27A or other digitally enabled sources) puts the signal through three times as many conversions, from digital to analog to digital to analog. The digital input path through signal processing did sound better than this analog input path, just as theory predicts. But we were pleasantly surprised by the AV8's sonic performance here, for the sonic difference was smaller than we expected.
We knew independently that the DV27A puts out a superb sounding analog signal, from its internal D/A conversion, so this comparison was chiefly a sonic test of the AV8's A/D convertors, at the input to its internal digital signal processing, that were being added as a new link into the signal path. The principal sonic difference we heard was some soft veiling of the overall sound, which in turn naturally caused some information loss, about subtle inner detail and spatial cues, and which slightly defocused sonic details which had heretofore been well individualized by the AV8, via its other signal paths. The AV8's overall sound was still very informative and enjoyable through this longest and most complex and brutal signal path. Indeed, even in this mode the AV8 was still very revealing of analog input cable quality, rewarding us when we employed the very best analog interconnects (the Von Gaylord interconnect won again here). And, yes, when we compared the
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