Yamamoto Sound Craft's vast catalogue of tuning products featuring ebony, alone or in combination with various metals and ceramics include just one set specifically designed to enhance CD players. Naturally most of their ebony cones and receiver bases should work well enough and might even be excellent in such applications, but Shigeki Yamamoto also makes this product specifically to work under CD players. This review seeks to establish whether they work, whether they work better than the competition, and whether they work equally well supporting different players of varying construction and technology.

The frequently changing CD players involved in comparing the CANOR Precision Tube CD Player CD2 VR+ with the two established players chez scribe gave more opportunities to establish whether the Yamamoto PB-4-2 is consistent from player to player, regardless of chassis construction, transport type or circuit topology. Thus, 5 months have elapsed in the process. The massive Yamamoto Sound Craft range makes a visit to their website both time consuming and entertaining. Yamamoto tuning devices appear to be more reasonably priced than many high end ranges, which may be exaggerated by the relative strength of the Yen and the Euro but remains true in other currencies. The Yamamoto product descriptions are refreshingly hype free too; Shigeki Yamamoto San merely describes the materials and suggests applications with a gentle hint of what might be achieved "The tightened sound is obtained from not having resonance on the metal pin and African ebony base" [paraphrased].

The metal pins are low profile cones turned from armoury grade bronze and gold plated. The African ebony is the higher density Ebony, relative gravity being 1:1.4 against South East Asian Ebony at 1:1.15. African ebony is nearly 30% denser than SouthEast asian of the PB-22 triangular bases). The familiar Shigeki Yamamoto argument that higher density ebony equals "tighter sound" while lower density South Eastern Asian ebony equals "lighter sound" will be modified by the presence of the bronze cone in place of Yamamoto's more usual ebony points.

Your old scribe's hackles are raised by Yamamoto supplying sets of four at 12,000¥; the day your old scribe buys a quadropod to support his cameras is the day I'll accept sets of four rigid support feet. There is no excuse for supplying sets of four as the fourth will never enjoy an even pressure and will at best simply not function as designed while at worst will actually rattle. A trio of Yamamoto PB-4-2 (named yamamoto PB-4-II on older packaging) is capable of supporting 45kg, which is as much as any CD player and all but the most insanely over engineered amplifiers. The Yamamoto Sound Craft PB-4 -2 are supplied packaged in quartets. Sets of four. Meaning one will live permanently in that overcrowded cupboard in very audiophile's listening room that contans all the spurious gadgets and gear that we own but never use. This unused footer cost the poor audiophool 3000¥ (25€, which is enough to buy good ingredients and wine for a meal), cost the planet some African ebony and manufacturing energy;
repeat after me:
Three feet good; four feet bad,
"Three feet good; four feet bad!" chorus plebs, stage left, for once in support of their old scribe.

Shigeki Yamamoto argues that the shape of the gold plated bronze cone and ebony receiver base stabilises the installed CD player rendering the "up-and-down field even"; the meaning, lost in translation software, seems (in context) to be that vibration is controlled vertically while stability is maintained. This reviewer's experience of stiff supports under CD players is that they maintain or enhance PRaT while lossy decoupled supports for CD players (and turntables), while dissipating or absorbing vibration, result in lost information or collapsing PRaT. Dual material or compound material (even when one is lossy) often achieve the best compromise

Shigeki Yamamoto manufactured his first product, the F320 wooden horn in 1982 and added the F280 horn soon afterwards. For more than a quarter of a century Mr Yamamoto has been developing and expanding a range of amplification, tuning and loudspeaker products, establishing the present Yamamoto Sound Craft incorporated company on August 1^st 1994 in Ono-city, subsantially capitalised and employing 6 people, a year after introducing his first amplifier, the Y-300SS. The company use CNC machining facilities for wood and are constantly refining their range, their most recent product, the F-280A is a revision of the 1986 model F-280 horn, 24 years after its introduction. The range includes horns for those compression drivers revered by Japanese audiophiles, from Golden age JBL and Altec to legendary Onken, all beautifully constructed from Japanese cherry wood. Sound quality is moot as folk happily pay similar prices for similar sized furniture for purely decorative furniture so 1700€ for a pair of soild carved 5.4kg treble horns (measuring 316x200x260mm) that would match the superb B&C DE-400TN-8 compression drivers being used as a reviewing tool even as your old scribe writes. However, your old scribe will try not to mention the hessian shopping bag again...
"Not mention the hessian shopping bag? He just did!" chorus plebs, stage left.

Sound Quality

It is well established by psychological research that we tend to report the sensory experiences that we are expecting. Hence, if we have a belief system that states that tuning devices in audio do not have any effect, we will not expect an effect and will be unlikely to hear an effect. Equally if we expect there to be dramatic effects and that balsa wood is the finest audio foot material we will tend to listen out for its benefits in comparison with a rival product of figured yew. Just as a belief that we don't like garlic in food will bias us against any foods known to contain garlic and be very surprised if told that a dish we have just enjoyed did indeed contain garlic. Reports of the subtle effects of tuning devices are greeted with angry villification by those who do not believe such effects could possibly exist and conversely, those who argue that the effects are at best subtle and often non-existent are greated by hostile accusations of deafness by those who believe that bits of wire and bits of wood are the elixir of life and the philosopher's stone.

It is much harder work comparing tuning products than real components. They have to be placed in the optimum position for each CD player. The differences are tiny, although they are real and repeatable. The tiny differences become exaggerated by A-B-X, B-C-X, A-C-X comparisons and the tedium inevitably means that after a while the reviewer is left alone with the task so that the X and blindness are no longer possible. The flat tops of the Yamamoto Sound Craft PB-4-2 contrast with the carbon fibre nipples of the Avondale Basis 15 and brass balls of the Waipuna Sound Myrtlefeet and therefore support their load differently. Many cone or point supports recommend point-down orientation under CD players but a few including these rivals work with minimal surface contact and therefore maximum pressure. In the Yamamoto PB-4-2 the flat upper surface maximises contact area (and minimises pressure) while the partner ebony cups (not sold separately) define the orientation of the gold plated bronze cones and their points. These cones rise out of a flat land margin, which further increases contact area with the CD player base while minimising the height of the cone. Shallower than Yamaoto's own MGB-1 and MGB-2 or Waipuna MYRTLEFEET, the PB-4-2 are still taller than most OEM feet and rival stalwarts like the Michell low Tenderfeet/Tendercups. Under valve CD players owners must ensure there will be sufficient clearance above the player to allow cooling air circulation.

In order to identify the effects of these feet solely as tuning devices, they are tested inserted between CD players and the Dissipating shelf of the Something Solid XR4. This rack features excellent shelf stability combined with good vibration isolation. These two design goals are often contradictory as measures to improve isolation usually result in loss of stability. Hence for the purposes of this test the main bulk of external vibration control has already been attended to, thus exposing the fine tuning capacity of the devices to control the internally generated vibrations from the mains transformer, spinning disc, laser tracking planchette, capacitors...

"Capacitors?" chorus plebs, stage left, "Did the old fool really just mention vibration generated by capacitors?"

You don't believe me? Try connecting a capacitor and resistor (in series) accross a stable amplifier and playing music through it. Deepending on the construction, the sound emanating from the capacitor will be recognisable to some degree, distorted and audible; this can only come from vibration. Thus these devices are being measured for their performance in controlling component vibration (including that excited by being in the soundfield from the loudseakers). Conversely a capacitor may convert vibration into electrical energy, particularly if the cap is biased by an AC voltage like an audio signal. Ho hum.

Comparisons are essential and among the best of the currently available crop I have tested are Yamamoto MGB-1 and MGB-2 magnetic bases under valve output stage CD players at much higher cost and the $39.95 Waipuna Sound Myrtlefeet represent the value end of the feet suited to valve output stage CD players. The £49.95 Avondale Basis 15 are optimised for Avondale's own AAA5 player so will really challenge rivals in that context.

The first test is with the Canor CD2 VR+ (review very soon) which already features carefully designed vibration control for analogue circuit boards and valve bases (double triodes and double rectifiers). Under this player positioning of the feet did not prove to be critical except when balancing the player on the magentic sprung feet, providing the existing feet do not interfere by contact with the aftermarket feet. The presence of valves in the analogue circuit raises vibration and microphony sensitivity, but the existing internal vibration control may negate any benefit from additional external vibration control measures. It is even possible, as has occured with some suspended subchassis turntables and additional compliant isolation that the additional external measures cause problems. Howver, the PB-4-2 are not compliant devices (not at any frequency that could react with the internal compliances - all mechanical systems resonate). Hence, the first test might be toughest of the three.

The differences under the Canor CD2 VR+ were tiny in each parameter and the combined numbers exaggerate the differences dramatically. This is a typical consequence of attempts to quantify qualitative data. The differences were unreliably reported in that reverse tests were not identical and null tests via no support produced virtually null results. Hence players like the Canor CD2 VR+ that are already equipped with considerable vibration control measures optimised for their internal components and layout are far less susceptible to benefit from additional tuning or isoaltion. However, in this instance the Yamamoto MGB-1 magnetic bases (the larger type with ceramic inserts needed due to the high mass of the CD2 VR+) did show their worth despite the extensive internal isolation built into the CD2 VR+ already. Time to try the rivals under less internally isolated players.

The Shanling CDT100c has been extensively modified by Chevron Audio (formerly trading as Chevin Audio) and is much more transparent than stock Shanlings that use numerous op amps. It is already equipped with Allnic Audio Absorba Gel Isolaters under the output valves and has the thick slab aluminium chassis (not the stainless steel chassis of some Shanling CDT100 variants) and a modestly isolated top-loading transport. Many previous experiments have demonstrated that this player benefits from 3 aftermarket feet, two under the axis of the rear row of transformer and choke covers, the third under the axis of the compact disc itself. The MYRTLEFEET proved their worth beneath this player in recent tests, so it is they and the Yamamoto MGB-2 magnetic bases as comparisons.

Numerically the PB-4-2 averages out equal to the more expensive MGB-2 (the lighter version of the magnetic bases without the ceramic inserts) but the PB-4-2 strengths lie in the musical fundamentals of the lower registers while the MGB-2 emhasises qualities of middle and higher registers. At over two to three times the price of the Waipuna MYRTLEFEET (depending on your location) the PB-4-2 should be expected to outperform the MYRTLEFEET, but given that only three of the packaged quartet of PB-4-2 were ever employed in this review, the PB-4-2 could be better value if packed in threes. As a trio the Yamamoto PB-4-2 would be double the price of the Waipuna MYRTLEFEET and would represent a clear and unambiguous improvement of a similar magnitude to the MYRTLEFFEET over the stock Shanling composite feet and are thus equally good value in this context. Now we travel from the valved high end to the realm of the solid state Flat Earth.

The Avondale AAA5 suffers from clanky casework and no visible means of isolation. It has its own matching Avondale Basis 15 feet, supplied sensibly in sets of three at £45 (sterling - YMMV) so no waste and approximately half the price of the set of four Yamamoto PB-4-2. The optimum positions for these feet are with their carbon fibre nipples pointed upward and engaging the steel baseplate of the player at the centre of the power supply torroidal transformer, the axis of the transport and the middle of the right hand edge. The flat topside of the PB-4-2 renders the centre of the transformer impossible, so the third PB-4-2 must be placed further back and more central.

The 0.5 marks arise because the averages of each change of condition, tested over several two-way runs, worked out nearer 0.5 than an integer. Each isolation foot demonstrated its strengths and weaknesses fairly consistently under whichever player was under test. However, the relative performanc of each set of feet was different under each player. This is only the second time this has happened in the TNT-audio vibration control tests, the other being the aforementioned subchassis turntable incident. All three types had considerable merit over the standard feet of each player; even though the Shanling makes an effort with cork type feet and the Canor has compliant feet, both are considerably bettered by these aftermarket feet.

The system dependency is not so great as to negate all reviews of tuning feet to the level of irrelevance of cable reviews, but is sufficiently great to imply that experimentation is needed by any enthusiast hoping to optimise every system component's vibration control and mechanical tuning. The differences are not like the clumsy tone control effects of some cables, nor are these feet sufficiently effective to obviate the need for a good rack. All the tests were conducted upon the shelves of the Something Solid XR4 which remains the reference benchmark in all-round performance. Thus the actual effects described here are in the tuning domain rather than as isolation from external struture borne vibration.

Differences are mostly repeatable and noticeable enough that when I reversed condition on one occasion, back to the Yamamoto Sound Craft PB-4-2 I was astonished that the numbers were not the negatives of the change the other way. Indeed for a couple of tracks I thought the PB-4-2 were considerably inferior to my previous judgements. On examination under the player it became obvious that I had not aligned one of the bronze comes correctly in the centre of the ebony disc and indeed the edge of the bronze cone was perched under a screwhead on the CD player's base causing it to slope and make poor contact. In this condition all the benefits of the PB-4-2 were lost, demonstrating that the set up is as significant as the design and materials and that owners must pay attention to this to obtain any benefit at all.

Yamamoto San also suggests the PB-4-2 work their magic under ampplifiers. Given his own range are valve products of various topologies the PB-4-2 were tried propping up steel cased single ended triodes, wood cased single ended triodes and steel plus aluminium. Here the PB-4-2 did not improve upon less expensive products (Yamamoto PB-9; PB-10; PB-20; PB-21) from Yamamoto's own stable and in the case of the steell chassis SET the lesser priced products were superior. It does seem that Shigeki Yamamoto's design expertise has been correctly applied in pursuit of optimaum CD player tuning and that is where the PB-4-2 work well.

Conclusion

The Yamamoto Sound Craft PB-4-2 work really well under CD players. All tuning devices are context dependent and the PB-4-II is no exception; there are few sets of CD optimised feet available at the 100€ish price point, most being about 50-75€ or into fancy expensive shelf territory. Ironically, if the Yamamoto PB-4-2 were to be sold in sets of 3 the price would reduce to 9000¥ or 75€ where they would be more directly comparable to a whole range of products. In that case the Yamamoto PB-4-2 would edge ahead on price-performance ratio under many more CD players, if not most. To better the Yamamoto PB-4-2 in most parameters under every CD player requires another Yamamoto Sound Craft product. The Yamamoto MGB-1 & MGB-2 magnetic floating bases. However, just as the magnetic bases lost out slightly in the PRaT stakes to the ERaudio shelf/cones, so the PB-4-2 held onto rhythm and timing slightly better than the MGB-2.

Rival products fall into five camps,

• stiff points down;
• stiff points up;
• compound products;
• linear springs (magnetic or mechanical);
• absorbant lossy blobs

Prolonged scrutiny of the results tables will indicate that there are clear benefits from the Yamamoto sound craft PB-4-2 where players have little or no internal vibration isolation, but that the situation is less clear cut with a high end player whose USP is its existing internal isolation. This is hardly surprising and it does confirm that the Canor CD2 VR+'s internal isolation has benefits and that the PB-4-2 have an effect that helps reduce the detrimental effects of vibration in players not already so thoroughly equipped. That the Yamamoto PB-4-2 achieved these results on top of the shelves of an already excellent isolation rack system proves their worth.
Recommended!