March 2014

Duelund Cast Pio (Paper In Oil) Copper Capacitor
Review By Jonathan Lo

  When audiophiles are asked to list some of the best capacitors available, the name Duelend inevitably makes the list. Duelund produces several audiophile capacitors. While the top-of-the line Duelund is technically the CAST-PIO-Ag, this silver capacitor costs $700 to 800 each, placing it beyond the reach of pretty much anyone. As a result, when one thinks of Duelend, it usually refers to Duelund CAST-PIO-Cu which is less dear at less than $200. They also make the VSF "Virtual Stacked Foil" capacitor and Alexander PIO capacitors, which are more affordable. This review pertains to the Duelund CAST-PIO-Cu capacitor, which is based on the virtual stacked foil design but adds waxed paper-in-oil dielectric among other enhancements.

Gone are the days of ancient paper-in-oil capacitors with overly-warm, larger-than-life images with rolled-off treble and wooly bass power. While these types of capacitors could still be quite attractive in certain situations to certain listeners, it would be difficult to argue they sounded neutral. Credit must be given to Jensen of Denmark who has kept the PIO flame going into the modern times with PIO capacitors that sound much more neutral while retaining that extra harmonic richness many audiophiles desire. Other companies have followed suit, and there are quite a few PIO options to choose from these days, which is a boon to the music lover. Still, it is not too difficult to tell when a PIO is in the circuit due to the unique sound characteristics, and other, more modern types of capacitors, especially Teflon, have demonstrated what most PIO's are missing in terms of microscopic resolution, frequency extension, and dynamic punch.

Enter Duelund
Coming from that perspective, the Duelund CAST PIO copper capacitors simply break the mold in terms of what a PIO capacitor is expected to sound like. Gone is the top-end roll-off and bottom-end bloat, and the level of detail resolution is unheard of in a PIO. In fact, the sheer amount of clarity and detail resolution the Duelund brings to the table is quite uncanny, not "for a PIO" but for any capacitor. Thankfully, the special naturalness and ease of a good PIO remains intact. Actually even more so, since there are no strange frequency response aberrations or quirks in the sound to distract the listener. What's even more interesting is how the harmonic richness and bloom is maintained while avoiding extraneous warmth, bloat, or opaqueness. The overtones and textures seem to be physical properties of the themselves, not a fuzzy, resonant ghost riding on top of the music like a halo, a problem often heard in very old PIO's that were not manufactured to exacting standards or perhaps those that have not aged well.

The way the Duelund presents strings is especially something to cherish. It is very difficult to get the balance correct between the resin of the bow and cavity of the body, but here there is the perfect amount of friction and glide, which presents the right amount of glorious texture without undue etch, all resonating from a warm, palpable body of the instrument. Those who lament the death of glorious strings in the digital era may have hope left yet. Speaking of strings and classical music, this capacitor is capable of localizing and layering the various sections of the orchestra in lateral, vertical, as well as depth dimensions, leading to a very engaging experience.

The Duelund distinguishes itself from some of the state-of-the-art teflon capacitors by the very way the sonic background gives the impression of perfectly calm lake without a single ripple, a calmness that permeates through the space between instruments, which in turn holds and supports the instruments firmly in place in the soundstage. There has to be a correlation between this sense of serenity and calmness and the extreme mechanical stability and damping present in the construction of the CAST PIO capacitor. There is no trace of blurred images or inconsistent tonal balance that can happen when parts are allowed to resonate or ring, and reading about how these capacitors are constructed, one can begin to understand why.

"The Duelund CAST Capacitor is a no holds barred flagship capacitor. The construction builds on the foundation of the Virtual Stack Foil design but does so with the addition of a proprietary WPIOdielectricum which necessitates several days of impregnation under very high pressure. This creates a form with incredible damping properties giving a mechanical stability hitherto unheard of. On top of this casting process, a ring of hard pressed paper strengthens the damping properties of the design helping music flow effortlessly."

Perhaps aided by the mechanical integrity, this capacitor's instrument separation and localization is top-notch, and while the presentation is beguilingly smooth and organic, when called for, there is plenty of metallic sheen and ring when such instruments are struck. In fact, this is one of the areas where CAST PIO seems to outdo most Teflon capacitors, which tend to lean a little more in the direction of metallic sheen and crackle versus the smooth and organic, to the point where sibilance and stridency can be a little more distracting, at least on less-than-perfect recordings.

There seems to be an interesting phenomenon that happens to the perception of time with the Duelund in place; time almost seems to slow down a fraction. This is not the same thing as if a musician makes an error and rhythm actually slows down; there just seems to be a minute fraction of a second more available between notes that allows more time for the listener to relax and sink into the music. The best teflon capacitors subjectively seem to present the "accepted" time flow with more distinct and harder-hitting transients and beats, but the effect is akin to a speed boat rocketting down the river energetically, splitting the water producing power waves. Duelund's effect is more like a beautiful sail boat with strong wind in its sails, still propelling forward but with more of a graceful glide. There are certainly types of music that will favor one type of presentation over the other, but both approaches are quite satisfying in their own way.

The Point
Before some users hastily slap in some Duelunds, give them a cursory listen, and declare them "overrated," I would strongly heed some words of caution. While various Teflon capacitors are usually notorious for taking forever to break in, the Duelund CAST PIO are not much easier to break in before they come to their full potential. Various types of capacitor burn-in devices or DIY contraptions may come in handy here, although even after that, this capacitor seemed to need a long time after being soldered into the final destination to fully "bloom," especially in terms of overall clarity.

Having evaluated a bevy of capacitors over the years, it would be difficult not to conclude that Duelund CAST PIO belongs in the very top echelon of capacitors. There really is no "best" when one gets to this level of excellence, just different roads to conveying the musical message. It would be perfectly feasible that different listeners may prefer capacitors of different build principles. For example, the very best Teflon capacitors may perhaps exhibit more imposing dynamics and apparent detail, yet the Duelund possesses something that is quite magical, i.e. a beautiful narration of the musical message without cyborg-like kinematics that perhaps gets in the way of true appreciation. Chances are, when one's most dear music is played via the Duelends, music will be enjoyed and savored to the fullest. That is certainly a worthy goal in my book.

Duelund Coherent Audio
Copenhagen, Denmark
CAST-PIO-Cu Capacitor
Price $180 to 200 range each depending on capacitor value
E-mail: info@duelundaudio.com
Website: www.DuelundAudio.com