I was able to get in a nice listening session with the new Duelund CAST silver-copper hybrid capacitors, and I wanted to give you the scoop on my initial listening impressions.

My apologies to Frederik for the lengthy delay in writing about his new hybrid silver-copper Duelund CAST capacitors, as it has taken much longer than I had expected due to the performance issues I've been having with my vintage McIntosh MX110Z modifications not going as expected.

Because of that, I've held off on writing about these Duelund CAST hybrid silver-copper capacitors, as I didn't want the performance issues of my MX110 to influence my ability to discern what the hybrids were capable of.

When I'm dealing with something that is beyond the state-of-art - like all of the Duelund CAST components are - I have to be absolutely sure that I am able to accurately articulate their performance, and I wasn't sure I could do that with the performance issues I was having with my MX110.

We've made enough progress with the MX110 now that I feel more confident in describing the performance of the Duelund CAST hybrid capacitors, and as a backup, my friend Leo has loaned me his vintage McIntosh C22 preamplifier, should the need arise to replace the MX110.

First a quick recap to set the stage:

It has been over six years since I bought my beloved Tannoy Westminster Royal SE loudspeakers from the good folks in Coatbridge, Scotland, which arrived here at Jeff's Place on December 30, 2009, where with the help of my good friend, Chad, we were able to get them uncrated so we could give them a listen.

I've been crazy about my Westminsters ever since that day - they are fantastic loudspeakers!

It has been over three years ago now that Frederik and I embarked upon our project to build high-performance crossovers for my Tannoy Westminster Royal SE loudspeakers using his amazing Duelund CAST components (capacitors, resistors, autotransformers, and inductors) - how time flies!

The Duelund-Westminster project that Frederik and I did was my first 'DIY modification adventure', and what a grand adventure it was to start with!

I was so impressed by the results we achieved using Frederik's Duelund CAST components that nothing has been safe from hot-rodding since then!

I chronicled the Duelund-Westminster project in real time here at Jeff’s Place, and I ultimately wrote everything up for feature articles at Positive Feedback (Part 1 – Issue 70; Part 2 – Issue 74).

When Frederik and I built the pair of external crossovers for my WRSEs out of his ultra-performance Duelund CAST components, we used the circuit schematics for the stock crossovers:

We replaced all of the stock components of the circuits with Duelund CAST components, which I laid out onto outboard crossover platforms.

Frederik also built a number of custom components for the Duelund-Westminster project, like the 200uF Duelund CAST Mylar Capacitor shown below that we used in the C4 position of the low-frequency section of the crossovers ...

... and the amazing Duelund CAST silver autotransformers that we used to maintain the adjustability Tannoy built into the Westminsters' high-frequency crossovers ...

... and finally, the exquisite pure silver 6.8uF Duelund CAST capacitors Frederik built for the C1 position in the high-frequency section of the crossovers.

The one-two punch of pure silver 6.8uF Duelund CAST capacitors in the C1 position injecting the music signal directly into the pure silver Duelund CAST autotransformers was like adding a supercharger to the already amazing Duelund CAST crossovers we had built for the Westminsters, and I was gobsmacked by huge increase in performance these silver wonders brought about.

That huge performance increase came at a cost that most mortal men could not afford, as the cost for each 6.8uF pure silver Duelund CAST capacitor was $10,289.48 USD - breathtaking!

For most of us, the cost of building a pair of outboard crossovers for our Westminsters using even the more affordable pure copper 6.8uF Duelund CAST capacitors stretched the budget to the breaking point, and the pure silver Duelund CAST capacitors were just out of reach.

It sure has been a wonderful experience hearing what is possible with the state-of-art pure silver 6.8uF Duelund CAST capacitors, but chances are that most of you will never get a chance to hear what they can do, and that's a shame, because they are magnificent.

Frederik told me that to help bridge the pure silver Duelund CAST capacitor performance-gap, that quite a number of his customers have been bypassing their copper Duelund CAST capacitors with a small silver Duelund capacitor, with very positive results:

“We are not blind to the fact that pure silver capacitors get very expensive at larger capacitances like your 6.8uF Duelund CAST silver capacitors, so the idea was to try to recreate some of the silver capacitor’s performance at a much lower cost. Quite a few of our customers like to bypass our larger CAST capacitors, so we thought that incorporating a small Duelund silver bypass capacitor into the CAST enclosure made the most sense to accomplish that."

Thus the new hybrid silver-copper Duelund CAST capacitors were born. The 6.8uF Duelund CAST hybrid copper-silver capacitors incorporate a 0.015uF silver bypass capacitor (that’s the hybrid part) into the 6.8uF Duelund CAST copper capacitor’s potted enclosure.

As a refresher, let me remind you how the hand-crafted Duelund CAST silver & copper capacitors are made.

In the Duelund CAST capacitors Frederik uses only pure annealed soft copper or silver foil in natural paper and oil, along with resonance control both inside and outside the capacitor. A capacitor is made using two foils with paper between the foils, which results in capacitance being created in the electric field between them. Each Duelund CAST capacitor is completely hand made in an incredibly labor intensive process:

“Foils of pure copper or silver are initially wound with paper to a certain value that is a good deal over the needed capacitance. Then the foil is put under vacuum pressure in an oil tank at high temperature for about a week, so that everything inside the winding undergoes vacuum impregnation and is permeated by oil. When this process is done, the resulting foil is wound by hand in a humidity and temperature-controlled room to an exact specification, and then it is placed back into the oil. Immediately after this process the winding is sealed by the use of a special lacquer, which is also used in the yacht industry to seal against moisture. This takes another week. During this process a ring of vacuum impregnated paper has been readied with a base of our CAST material.”

“The winding is heated and then placed in the ring & base assembly and CAST material is poured on top of it in five stages, with air bubbles in the CAST material being forced out by applying a very precisely controlled flame to the surface (yes really!). This process takes another week. Following this step the capacitor is measured and checked (as it has been at every step along the way), and if everything is ok, then we ship it to the customer. The total production time is typically six to eight weeks.”

So inside the new Duelund CAST hybrid silver-copper capacitor there are really two capacitors enclosed within, the exotic copper foil capacitor that is being bypassed, as well as an equally exotic silver bypass capacitor. They are both potted together as described above, which damps any resonance effects you might otherwise get.

If you look closely at the lead for the 6.8uF Duelund CAST hybrid silver-copper capacitor above, you can see intertwined leads from both the bypassed pure copper foil capacitor & the pure silver bypass capacitor hidden within the CAST potting.

So what do the hybrid silver-copper 6.8uF Duelund CAST capacitors sound like?

To characterize the performance of the new hybrid silver-copper Duelund CAST 6.8uF capacitors ($744 USD/each), I installed them into the C1 positions of my crossovers and listened to a variety of music with them, and then compared their performance to that of the pure copper 6.8uF Duelund CAST capacitors ($700 USD/each), and pure silver 6.8uF Duelund CAST capacitors (approximately $10,200 USD/each, but pricing depends on silver spot prices when you order them).

My initial impressions are that the hybrid silver-copper 6.8uF Duelund CAST capacitors sound very similar to the pure silver 6.8uF Duelund CAST capacitors in the higher frequencies (upper midrange on up), yet they maintain the overall sound of the pure copper 6.8uF Duelund CAST capacitors in the upper-midrange on down.

My Tannoy Dual-Concentric high-frequency drivers' love the pure silver 6.8uF Duelund CAST capacitors in the C1 positions of their high-frequency crossovers, resulting in a performance level that is almost indescribably good, being smooth, rich, natural, detailed, shockingly transparent, and incredibly musical. You don't hear even a trace of grain, grit, brightness, harshness, etching, or other nastiness from the pure silver 6.8uF CAST capacitors, in fact their performance is so lofty they're just otherworldly!

Here's the good news: I think that most listeners will find it challenging to hear any differences between the hybrid silver-copper 6.8uF Duelund CAST capacitors and the pure silver 6.8uF Duelund CAST capacitors in the higher frequencies (upper-midrange on up), so the hybrids can be a very cost effective choice for injecting some of that pure silver magic into the high-frequencies.

You can easily hear the difference between the hybrid silver-copper 6.8uF Duelund CAST capacitors and the pure silver 6.8uF Duelund CAST capacitors from the upper-midrange on down, where the hybrids sound identical to the pure copper 6.8uF Duelund CAST capacitors that they are based on.

However, the way I hear it is that the pure silver 6.8uF Duelund CAST capacitors are still in a league of their own by a substantial amount, which I guess is not too surprising. I have lots & lots of hours on my pure silver 6.8uF Duelund CAST capacitors, so they are silky smooth from top to bottom, and they have developed over time a sophisticated sort of nuance & articulation about them that is unlike anything else in my experience.

The hybrid & copper Duelund CAST caps don't have nearly as much time on them, of course, but I suspect that over time they too will continue to smooth out and become more nuanced and articulate like the pure silver Duelund CAST caps, and I will continue to report as I get more time on them.

I would say that all of Frederik's Duelund CAST caps, whether the hybrid, silver, or copper, are in a league of their own compared to anything else, and each are amazing accomplishments.

I think that being able to choose among the hybrid, pure copper, or pure silver Duelund CAST capacitors in a crossover circuit will provide a very powerful method for voicing and optimizing the performance of a crossover to get the very best in performance from it.

After listening to the hybrid, pure copper, and pure silver Duelund CAST capacitors, all I can say is "Well done, Frederik!"

Ok, that's it for now on my preliminary listening impressions, I'll have more to say later.

Many thanks to Frederik for letting me experience these amazing capacitors and allowing me tell their story here, and thanks to you for stopping by!