Hardware Reviews

Auva EQ: splendid isolation

Stack Audio Auva EQ isolators

Stack Audio Auva EQ isolators

As a long time fan of isolation proper it’s gratifying to see so many products on the market that are genuinely trying to stop the transmission of vibration into audio components. For far too long we were told that spikes were isolators whereas in fact they are the opposite, a conduit for transmitting vibration into and out of components. If you think about it, a spike is a fancy nail, when you nail a speaker to the floor the energy in the cabinet goes into the floor and this energy is transferred to all the other things sitting on the floor, not least the other loudspeaker. Max Townshend understood this better than most and developed numerous isolation devices that broke this connection, devices that actually isolated components and speakers from whatever they were sitting on. Stack Audio have also grasped this fundamental fact and launched their Auva range at the beginning of last year with speaker isolators including the Auva 70.

More recently Stack unveiled the Auva EQ feet for component isolation, these are sold in sets of three or four and combine two technologies in an effort to create an energy barrier. The first, Auva, is what they call particle impact damping technology, and describe as “throwing a ball into soft sand –the sand absorbs the energy from the ball, preventing it bouncing.” Essentially it absorbs energy rather than transmitting it. The second part of the Auva EQ is a silicone rubber suspension that supports the machined aluminium shell and this provides compliant damping.

Stack Audio Auva EQ isolators https://the-ear.net

The Auva EQs are 50mm in diameter and 28mm high with a black anodised finish and are available in three weight ratings, these range from under 4 kg per isolator up to a maximum of 15 kg. You divide the weight of your component by the amount of feet required to establish which version to get, so a 20 kg amplifier would theoretically require three CSA 2 (4-10kg) isolators. I asked Theo Stack about whether three or four feet is optimal and he said “It is not as simple as recommending three vs four, it is usually up to the weight distribution of the hi-fi. If it comes with three stock feet, we would usually opt for three, however, if has four stock feet, we would recommend using four to align with the manufacturers design. Equipment such as amps often have a large amount of their weight on a certain side, if there is only one EQ on this side, it may struggle with the additional weight applied.”

You place three or four Auva EQs under a component such as an amplifier or DAC with the rubber on the supporting surface and the metal top of the EQ under the component feet, if you have sufficient EQs of course. Max Townshend’s mentor in this area was Professor Jack Dinsdale (inventor of the Rock turntable), he had a ‘law of more stuff’ that went something like: the more stuff you put between a source of vibration and the device requiring isolation, the less will get through.

Stack Audio Auva EQ isolators https://the-ear.net

Sound quality

Stack provided three Auva EQs for me to experiment with so in all but one case the metal caps were supporting the chassis rather than the feet of the components being auditioned. The first piece I chose was a Melco N10 operating as a server and streamer, effectively providing the source for the digital system. This is a two piece device and I put the Auva EQs underneath the transport rather than the power supply. The effect was very positive with an increase in detail resolution that was audible as extra reverb and greater clarity of quiet sounds. This has the effect of filling in the gaps between the fundamentals, of rounding out acoustic instruments including voices, and making the presentation more vivid and realistic. The N10 contains a spinning disc drive which may make it more sensitive to vibration than solid state alternatives, but it’s usually the quartz crystal clock that is intrinsic to the process of digital streaming that is in the greatest need of a mechanically quiet environment.

Putting the Auva EQ feet underneath an Auralic Vega G2.2 DAC instead of the four sprung feet that it usually sits on proved to be worthwhile as well. The springs on this weighty component are quite stiff and do not compress very much under the 9.3kg spread across them, I suspect that the Auva EQs are more compliant (softer) because the sound opened up quite dramatically when they were used. The sound became more spacious which allowed female vocals to sound more nuanced and expressive. This sort of change can sometimes be at the expense of solidity and power but that was not the case here, the DAC continued to deliver a typically powerful performance.

Stack Audio Auva EQ isolators https://the-ear.net

With the Mutec MC3+ USB reclocker which is a much lighter unit at 1.35kg the effect of elevating it with the Auva EQs was to make the sound bolder and more dynamic. With the heavier (2kg) Ref10 Nano word clock the result was closer to that found with the previous electronics and mainly related to spaciousness and three dimensionality of imaging.

Moving over to the analogue source I tried the three Auva EQ feet under a Tom Evans Groove+ SRX MkII, this acrylic cased phono stage has four rubber feet so the Stacks were placed against the base with the rubber feet on the wooden rack shelf beneath. This had the opening up effect again with a clarification of detail making it easier to hear what was going on. It felt like a tonal lift that worked well with a relatively clean recording but might highlight shortcomings with less sophisticated productions. The bass was not restricted but rather leading edges were better defined and this increased the sense of articulation across the board.

Stack Audio Auva EQ isolators https://the-ear.net

Under the three feet of a Rega Naia turntable (4.7kg) the Stack isolators allow the sound to open up rather nicely without any apparent tonal change, just larger soundstage scale with stronger image projection. Crucially they also reveal that this turntable capable of even better timing when separated from vibration in the supporting surface. The Naia has no suspension of its own so is more likely to ‘read’ the energy in the support, but its high stiffness and low mass mean that its less sensitive than most, yet the Auva EQs clearly benefitted the sound it produces.


These Stack Audio feet may look simple but the results suggests that the combination of silicone rubber and their particle damping system works and works well. I note that the weight ranges are related to the silicone inserts and that these can be purchased separately should you switch components, making them usefully future proof. The Auva EQs are priced competitively considering their British made origins and proprietary tech, not to mention that they are built and finished to a high standard. If you want to get a better idea of what the components in your system are capable of I suggest you give them a try.


Type: isolation feet
Weight: ranges:
CSA 1: 0-4kg (0-9lbs) per isolator
CSA 2: 4-10kg (9-22lbs) per isolator
CSA 3: 10-15kg (22-33lbs) per isolator
Dimensions HxD: 28 X 50mm
Warranty: 2 years

Price when tested:
£150 for 3
£198 for 4
Manufacturer Details:

Stack Audio
T +44(0)1626 24 9005


isolation feet


Jason Kennedy

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