Influence of FLAC Compression Level on Sound Quality
In our previous series on computer audio (TAS Issues 218–221), we reported a sonic degradation when WAV files were compressed into the FLAC format. These results were disputed by those who claimed this was impossible since once the files were converted back to WAV, the files were bit identical. We made the same measurements on the digital files ourselves and obtained the same results. Yet we stood by our subjective results then and continue to do so now. The problem is that measuring digital files themselves has no bearing on the ambient jitter coming from a variety of sources generated within a computer, and it does not reveal audible sonic differences. Only when the digital information is transformed to analog by the DAC do these sonic differences become manifest. So we decided to ask whether we could make meaningful measurements using the subjective and objective methodology we described in Part 1 of this new series. The degradation that occurs when playing FLAC files over a range of different compression levels as assessed with these two methods is shown in Figure 1.
A serious degree of sonic degradation is heard when WAV files are compressed using FLAC. It appears to follow a regular, negative hyperbolic pattern, whether quantified subjectively or by the more objective technique of height measurement. These results agree with our previous finding that FLAC compression of a WAV file (at level 5 in dBPA) degrades playback sound quality (SQ) from a typical PC server (see TAS, Issue 220, Feb. 2012). Under the circumstances of this experiment, we found that the height method was significantly more sensitive than our subjective method. We also show the actual percentage compression at each setting within dBPA. Counterintuitively, it can be seen that there is no quantitative proportionality whatsoever between the degree of compression and sound degradation. We have also examined the effect of the so-called “U” or uncompressed setting on sound quality found on recent versions of dBPA. This setting is not the same as the “0” setting, and it produces a file about 1% larger than the original WAV file (data not shown). The sound quality of this file is still not equal to the parent WAV, but the degradation is close to the detection limits of either of our two methods, something on the order of about 5 points on our subjective scale and within 2 inches on our height scale. As for why this degradation occurs when using FLAC files, we can only speculate that real time format decompression somehow creates an extra drain on computer CPU resources that occurs concurrently with the digital- to-analog conversion step, presumably mediated by an increase in system jitter. Given the apparent audibility of pico-second and even femto-second jitter, perhaps it should come as no surprise that the ear can detect the effect of lossless decompression on SQ. The magnitude of this degradation might well vary with the number of other background processes running simultaneously on a given computer. The solution to this problem is to convert compressed files to WAV, store to the hard drive, and use these files for critical listening. This is what we have done for all of our high resolution downloads1. On the basis of these results, we strongly encourage all commercial download sites to offer the customer the purchase option of a completely un-manipulated WAV file or, for purposes of metadata convenience with some playback programs, minimally compressed FLAC files using the U setting found in dBPA, despite commercial resistance to following this advice.
To BB or Not to BB, That is The Question—A Do-It-Yourself Tweak
In the course of using the NuForce Ref 9 V3 SE’s, which are fairly small and light weight Class D amplifiers, we found it difficult to keep the amps in a stable position when using heavy cabling while balancing the amps on various cones. We resorted to placing heavy rocks or paver bricks on top of the amps to keep them immobilized. We recalled that VPI once made a device with a laminated iron core, enclosed by wood, called the “VPI Brick” that was supposed to improve the sound when placed on top of electronics. This effect was explained by the ability of the iron to attract magnetic flux lines and eddy currents away from sensitive circuits within the device. Many years ago, one of the authors did an experiment in which up to 7 VPI Bricks were placed on top of a then state-of-the-art Accuphase DAC, one at a time. A clearly audible improvement was heard with each addition of a brick up until the seventh one, where the audible effect was small enough to be questionable.
Recently while in a local big box store one of the authors serendipitously spotted packages of zinc-coated steel BBs in various-sized plastic containers made by the Daisy Corporation. The largest package contained 6000 BBs, weighed nearly 5 pounds, and sold for $9. The light bulb went on and we eventually bought several packages to test for sonic effects as well as for stabilizing our equipment.
Much to our pleasant surprise, the BBs seemed to significantly improve the sound. As a control we compared this effect against our rocks to determine if the effect was solely due to mass. The rocks did absolutely nothing for the sound. We then started adding multiple containers of BBs, one-by- one, to each piece of equipment in our signal chain (PS Audio Power Plant Premier line conditioner, DAC, BSG qøl processor, and amps) all to marked sonic benefit. We even slid a box under the power supply of our computer server. We ran another control in these experiments in which we replaced several packages of the steel BBs with ones containing copper BBs with the same number, diameter, and container size. In contrast to the zinc-coated steel BBs, the copper BBs degraded the sound regardless of placement. We believe this is likely due to an inverse Faraday shield effect of the copper BBs acting to reflect internally-generated electromagnetic fields back into the equipment chassis.
In order to determine the maximum BB effect, we added individual packages of BBs one at a time. For this test BBs were repackaged into small plastic tackle boxes (available from the sports section of big-box department stores). The containers varied in size from 4″ x 7″ x 11/8” to 3″ x 5″ x 1″. After optimally loading up all of the other devices in the signal path (PS Audio Power Plant Premier, the BSG qøl processor, and the NuForce amps), we examined the cumulative BB effect on just the PS Audio PWD DAC. We incrementally added BBs at positions 1 to 7 on top of the DAC as shown in Figure 2A, and at positions 8 and 9 beneath (Figure. 2B). Since all the electronics were supported by Nordost BC Sort Kones, care was taken to shim the lower containers so that they were in close proximity but not touching the underside of the DAC, which can be seen in Figure. 2B.
For this experiment we chose to use track 5 from the Misa Criolla recording (ripped from the original CD and up-converted using iZotope Adv. v2 to 192 kHz/32-bit) since the position of the sopranos in the choir displayed a greater range of heights than the Chabrier or any other recording with which we were familiar. The results of this experiment are shown in Table 1. By using the Misa Criolla cut as our standard for comparison, we were easily able to identify height differences with each added pack of BBs. The height position of the sopranos above the midrange driver of the B&W 802 speakers is noted in column 2 and is reported both as the sum of the distance above the midrange up to the room height plus the distance folded forward toward the listening position along the ceiling (the center of the speaker midrange to ceiling height of 44″ and the forward projection distance are also shown in brackets). The equivalent subjective SQ point difference is shown in column 3. Column 4 highlights some first impression comments about specific elements of SQ change that caught our attention during the test. A variety of other characteristic SQ changes, including harmonic, positional, and focus characteristics of specific instruments and voices were also monitored and noted during testing.
In this test sequence, the most marked improvement was observed with the first few BB boxes added to the DAC. As more boxes were added, the SQ improvement became more subtle. If it had not been for our familiarity with the music, it would have been harder to notice the incremental changes between the 7th, 8th, and 9th boxes, but even here there was a subtle improvement to be heard. On this piece of equipment the BBs never conferred a negative sound quality. The pitch and tonality of the music and voices stayed constant, whereas the focus, clarity, ambience, sweetness, and emotional involvement continued to improve with the addition of more BB boxes. At the same time a subtle harsh quality was decreased, which we could only recognize by its absence. Superficially, this effect on harshness might appear to be small. However, from the standpoint of being able to emotionally connect with the music, its effect in these experiments and others we have done is pernicious and more disturbing to the brain than one might at first realize. Overall, the total SQ improvement of adding all the BBs was clearly in the “very large” category and, according to the cumulative point scores shown in column 3 of Table 1, is in the same range as the difference in sound between a CD and its corresponding original high-resolution download or SACD. We know of no other tweak that produces a greater sonic return on one’s investment. From an emotional point of view, we believe this tweak benefits the sound of digital to nothing less than a remarkable degree. Whether this is large enough to convince analog proponents remains to be seen. All we can say is that the effect on DAC performance produces authentic goosebumps of pleasure.
After doing the BB sequence comparison noted in Table 1, we explored the positioning impact of BBs under the DAC. We removed all BB boxes—this resulted in a soprano position of 39″ (our previous baseline without BBs as noted at position 0 in Table 1). We then added two boxes only at positions 4 and 5 on top of the DAC. This resulted in a soprano position of 56″ (44″ to the ceiling +12″ projected forward along the ceiling) and a very noticeable improvement in SQ. We then removed all BBs from the top of the DAC and positioned the same two boxes at positions 8 and 9 under the DAC. As before, we added spacers (empty CD cases) under the BB boxes to obtain the closest proximity to the bottom of the DAC and the internal electronics. This BB positioning resulted in an increase in soprano height to 72″ (44″+28″) and an even greater SQ improvement compared to two boxes placed on top of the DAC. Characteristics such as clarity, focus, sweetness and emotion were all improved. We suspect the greater SQ improvement achieved by the bottom BBs was due to the closer proximity of the BBs to the circuit boards and power supply of the DAC, which are nearer to the bottom of the enclosure. When using BBs, it is important to try positioning under electronics as well as on top, although trial and error will be needed to determine the best BB positioning for each piece of electronics in your system. We show an example of the placement and number of wooden BB containers on a BSG qøl processor In Figure 3.
Lastly, there are two other aspects of these results that we would like to point out. On some pieces of equipment we have tested, the position of BBs in certain areas can actually degrade the sound (for example, the middle top areas of the PS Audio Power Plant Premier and the Esoteric K-01 CD/SACD player,) so care must be taken to conduct listening evaluations during placement of each container of BBs. We have found that even a 1″ change in position can be audible. Moreover, it is possible to overdo the number of BB containers on a given piece of equipment, which can have the effect of reducing musical dynamics and subtle overtone reproduction while still retaining perceived clarity. When perusing the results shown in Table 1 the reader will note in column 2 that for the addition of BBs at positions 7 through 9, we reached the maximum height value for the sopranos. As we have discussed earlier in Part 1 of this article, we have left these results to stand, on purpose, in order to emphasize the importance of sonically handicapping a system to a great enough extent that all height measurements fall within the limits of the recording itself. In this case we underestimated the required range.
Cones, Cones, and More Cones— Mechanical Decoupling and Vibration Control
The benefits of isolating equipment from external vibration have been known for several decades. One of the earliest specialty products introduced over 30 years ago were the ubiquitous Tiptoes (circa 1984) commercialized by Steve McCormick of the Mod Squad. These devices were machined from aluminum in both tall and short conical versions. Some audiophiles noted improved definition with the use of Tiptoes (usually three or four placed under electronics and speakers). Gradually, it was recognized that these cones had a resonance in the upper midrange that imparted an unnatural and annoying harshness to music. A later refinement of this concept was introduced in the form of Goldmund Cones that implemented a “mechanical diode” principle claimed to drain away spurious mechanical vibrations generated within an equipment chassis while resisting the external influence of structure-borne vibrations in the opposite direction back into the equipment, hence the mechanical diode analogy. Goldmund Cones are no longer manufactured, but at the time, they were a sophisticated product, consisting of a machined-steel body terminated with a higher-density steel tip. Whatever natural resonant frequency that remained in the device was suppressed by a central filling of an elastomeric damping material. Placing the equipment on cones on top of a high mass substrate (for example, a 2–3cm-thick granite shelf) further optimized the beneficial effects. In direct comparisons to Tiptoes and other isolation devices of that era, the Goldmund Cones offered a significant improvement in overall sound quality with improved imaging, wider soundstage, tighter bass response (especially when placed under speakers), and better detailing. For many years these cones bettered many newly-introduced types of footers we evaluated. But finally they were surpassed by both Nordost Sort Kones and Stillpoints.
Initially we chose to compare three examples of product in this category that were comparably priced and that we already owned: our older, now-discontinued Goldmund Cones, along with the current Nordost BC Sort Kones in Bronze and Stillpoint Ultra Mini SS footers. We decided that it would also be a good idea to try footers at a higher price point. Through the kind auspices of Bruce Jacobs of the Stillpoints company and Paul Ritchotte at Nordost Corporation, we obtained samples of Stillpoints Ultra SS footers and Nordost TC Sort Kones (titanium) for testing. It is worth noting that all of these footers, except the original Goldmund Cones, use small ceramic balls (from 1 to 3 for each footer) as part of their isolation concept.
In Table 2, we show the comparative results of both our subjective and objective methods for evaluating the effects of various equipment support devices. Although Goldmund always recommended a tip-down orientation for its cones, Nordost and Stillpoints consistently recommend a point-up orientation. We tried the footers in both orientations and chose that which sounded and scored best. Accordingly, the best-sounding footer orientation is also indicated in Table 2. It came as some surprise to us that we frequently disagreed with the manufacturer’s orientation advice.2 We rank the degree of sonic improvement in order of increasing quality in the table. The retail cost is included as a purchasing aid for those inclined to act on our findings.
In System 1, where all of this testing was done, the two NuForce monoblock amplifiers and BSG qøl processor were placed on Nordost Bronze Sort Kones. System sound quality was sensitive to footers placed under the PS Audio AC regenerator/line filter, so an extra available set of Nordost Titanium Sort Kones in a point-down orientation was used for this piece of equipment. The B&W 802 speakers were fitted with the manufacturer’s support spikes. Given this system configuration, the PS Audio PWD DAC was used as the variable to test the effect of each set of isolation devices. With this experimental setup the ability to detect significant differences and create a rank order of merit was easily accomplished using the objective height method.
Without the application of cones or BBs (intentionally removed from the DAC for this comparison), the PS Audio PWD had satisfying SQ, but it did not reach the levels of musicality of which it is capable. With Goldmund Cones, our prior isolation standard, a very substantial jump in the sound quality of the PWD was observed coincident with a large increase in the height measurement. The Nordost Sort Kones BC improved the sound further by removing a slightly harsh quality exhibited when using the Goldmund Cones, while simultaneously increasing clarity, attack, and harmonic overtone structure. This improvement was similar to that heard when moving from no cones to the Goldmund Cones. Switching to the Stillpoints Ultra Mini SS footers resulted in another level of improvement, conservatively at least as large an increment as that between the Goldmund and Nordost cones. Yet, this last upgrade seemed to lock in a harmonic correctness and complexity that created an immediate increase in emotional connection to the music and the soloist. In all of these comparisons, it was amazing to hear immediate improvements in SQ that were obvious in a single A/B sonic comparison and which were even more apparent in the height measurements.
We then began to test the higher-priced tier of footers. Of the two types of footers tested, the Nordost Titanium Sort Kones and the Stillpoints Ultra constituted one of the rare cases where we could not distinguish any difference between the top two performers. The Titanium and Brass Sort Kones look identical except for the construction material, but in direct comparison the Titanium Kones easily achieved a 30 point SQ improvement over the Brass Kones.
In discussion with Bruce Jacobs, the use of granite shelving in our systems was questioned. He suggested that the Stillpoints product might sound better with a dense piece of flooring bamboo inserted between the footer and the granite. We obtained 4″ x 4″ x ½” squares of this material for additional testing. When the Stillpoints Ultra footers were used in our preferred inverted position in combination with the bamboo between the footer and the granite shelf, we instantly observed degradation in SQ, with a loss in transparency and focus, along with a 13″ height drop in our soprano measurement. When we used the bamboo with the same footers in a non-inverted position, the SQ was found to equal that found with the inverted footer position in direct contact with the granite shelf, so the results shown in Table 2 stand as reported. Nonetheless, if you are using wood or other types of shelving material, it is best to try all footer products in both orientations—you must do the experiment yourself to determine the best sounding orientation in your particular circumstances.
Although we chose just the PWD DAC for testing the effect of footers on sound quality, we would point out that the addition of footers of some sort under each piece of equipment in the signal path is cumulative. Jacobs also pointed out that using the same manufacturer’s footers throughout the system (rather than mixing them as we did in out tests) can produce synergistic results. To test for this possibility and also to see whether there might be any subtle but cumulative negative properties as we increased the number of support devices, we compared a system equipped entirely with the Nordost titanium Sort Kones against one equipped entirely with Stillpoints Ultra SS footers. In addition to assessing height, we also paid close attention to our subjective criteria, particularly dynamic range and harmonic overtone structure.
After the more limited testing shown in Table 2 and the near identical performance of the two brands of the more costly competing footers, we were truly surprised at the subjective SQ advantage exhibited by the Nordost titanium Sort Kone-equipped system compared with the Stillpoints Ultra SS-equipped system (see Table 3, lines 1 and 2). Despite this obvious sonic difference (estimated to be somewhere between 30 and 50 points better on our subjective scale, a difference falling within our definition of the very large category of sonic significance) we could detect no significant difference in our soprano height scale. We suspected that we might have run out of available headroom with this sonic marker as a result of a real recording limitation in capturing the original performance. To test for this possibility we decided to handicap the system performance in order to reduce the height of the sopranos by making certain modifications to the standard system setup. We removed the BBs from the top of the DAC (see Fig. 2B) and replaced the Wireworld Platinum USB cable between the computer and USB to SPDIF adapter with a generic computer-grade USB cable. We now could observe a major soprano height difference of 23″ while still retaining a subjective SQ point advantage in the 30 to 50 point range observed with the Sort Kones prior to handicapping.
We chose to focus our attention on the Nordost and Stillpoints products because, in our experience, we believe these two brands represent the best of the breed of support devices on the market today. As we were unable to detect a sonic difference when comparing the effect of the Nordost titanium Sort Kones with the Stillpoints Ultra SS footers on just the DAC (see Table 2), the measurements and SQ changes shown in Table 3 came as a complete shock. Our involuntary, non-intellectual, non-left brain emotional response was totally unexpected and unmistakable.
While we propose that our height measurement system is a new and very useful way to rank performance variations, a tape measure (or for that matter, an oscilloscope or distortion meter) cannot quantify or evaluate the black-and-white difference that exists between being emotionally connected with our music versus not connected. Only the human brain has that capacity.
We would caution that these results could vary with the composition of equipment stands and the internal construction of the equipment used. For example, differences in the isolation of internal circuit boards, the thickness and resonant frequency of circuit board material, the proximity of circuits to shielded or unshielded power transformers, and even the layout of circuit traces could yield different results.
The conclusion readers should draw from our particular findings is that they must compare different footers in their own systems if they want to get the best results. The most important fact is that adding good footers throughout a system can very easily be more beneficial than spending far more on a particular electronic component, and can improve the performance of any existing device, regardless of price. We want to stress without equivocation, that, in our opinion, the full effect of treating a complete system with the best footers one can afford is revelatory and the sonic value they confer on any good system is money wisely spent.
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