After you read this, perhaps you would expect a better system to test the capacitors. So today, I visit a friend, and test the capacitors on his system. We can call him, Mr. X. Here is some brief of Mr. X audio system.

Below is the power amplifier. Powered with RS241, RE604,and 6J5. Rectifier is RGN 2504 (later we try Klangfilm RGN 4004). OT is Tango. Currently powered with Jensen Copper Foil Capacitor and old NOS Western Electric capacitors. FYI, RS241 is claimed by most audiophiles as best sounding tube amplifier (forget 300B or 2A3) – and it’s really proven, if you have chance to hear it. This is an ultimate Single Ended tube amplifier (if you really know what do RS241, RE604, and 6J5 really mean to an audiophile).


We move to pre-amplifier section. We have Tungsol 26 in Globe (rare, eh?) with (I think) RGN2504 there. Also, one of the finest pre-amplifier.


Conrad-Johnson Phono Stage.


A turntable as source? Why not? We did enjoy the Norah Jones (Feels Like Home) from the Vinyl.


Audio Research CD7 as Digital source.


Lowther EX4 in Fidelio enclosure. Well, it’s time for a full range 🙂

Btw, do you notice a “special” appearance from this EX4?


Tweaking time!!!


A final battle, between Jensen Copper Foil Paper Tube and Duelund CAST PIO.


A complete system appearance for testing the capacitors.


How do they sound it this system? Let’s start.


This classic Jensen Pure Copper Foil is used as a benchmark for current popular – most used – coupling capacitor. It has warm sound, good vocal, adequate treble, but definitely less detail and sounds too crowded (if you have ever heard the others on this capacitor comparison session). For its affordable price, around US$ 73.9/pairs, this is the one that you should try if you expect a warm sound but with adequate treble.


The highest level from Mundorf, the MCap Supreme Silver/Gold/Oil. Not much different from yesterday findings, this capacitor has good staging and good emphasize in high frequency notes. While the oil inside this capacitor will still maintain the vocal from becoming to “cool” as the VCap. If you expect a live sound, while still expecting an adequate mid-vocal (don’t expect it would be too sweet), then this could be yours. But remember, with US$ 177.2/pairs, this is considered as serious capacitor!


This VCap TFTF is praised as one of the best signal capacitor. I think I have to agree that this is the most revealing capacitor. Teflon is well known as expensive capacitor, no surprise if VCap sells its 1uF/600VDC TFTF at US$ 279.98/pairs. But sorry I have to say, on our current testing system, this VCap can’t fight much with others in terms of musicality. Not because this is a bad capacitor (someone will throw something to my head if I say word “bad” for an US$ 279.98/pairs capacitors), but simply it doesn’t match with our testing system. Think like this: You already have a salty noodle, then you add some more salty soup. How does it taste? We already have a quite revealing system with RS241, with addition of VCap, it will become even more revealing (and no longer enjoyable). This is the thing that shouldn’t happen in audio. Use VCap on “dull” system and it will work best! I’m thinking of 300B which somehow has too warm vocal and less clarity – with VCap – I believe it will work best to reveal 300B weakness. And perhaps on pre-amp with 5687 or 6DJ8 tubes which most of the times – shares similar character with 300B. Back to our system, VCap sounds too thin, cool, and less emotion (we hear the detail, but we don’t hear the music). We admire its detail and revealing character (I think it’s the best compared with others in this round up), but simply not a perfect couple for our current testing system.


Jensen Pure Copper Foil Paper Tube is the latest generation of Jensen. I think, it shares similar build technique (construction) with Duelund CAST PIO (similar color appearance to). According to our source at Duelund (see the note at the end of this entry), Duelund has different internal construction and different material inside – despite the similarity of appearance with other capacitor. My subjective sound test proves this to be true. Back to the Jensen Pure Copper Foil Paper Tube, it has excellent musicality. Vocal is very warm and “swing” following the music. But one thing we have to underline (after extensive testing with Duelund CAST PIO), this Jensen has less resolution (not a real treble cut off, but just less detail). Just like a picture with too high compression. Overall, both Jensen Pure Copper Foil Paper Tube and Duelund CAST PIO will be looked similar in general. But after you zoom it in, you can see that the Duelund CAST PIO has better resolution. Duelund CAST PIO will maintain it sharp picture while the Jensen already shows garbled picture with same zoom-in ratio. The different may vary, depends on the music and your equipments. If your music has a lot of brass and cymbal or other micro details sounds, the different could be very significant (like on our Carmen Gomez Meets Kharma track). But the different also could be in a “small” margin (like if you are a vocal lover of Ingram Washington track). To avoid any confusedness, let me explain the above phrase a little bit: On a “not to extreme” resolution system, and if your background are a mid-vocal tube lover tubey sound – and better if never ever heard Duelund before), the Jensen Pure Copper Foil Paper Tube should be fine for you. We are talking about most tube fans which currently prefers Audio Note or Jensen on their coupling application (on my experience, they never heard Duelund before). With its “affordable price” (again, the definition of “affordable” here only works if you are comparing it with US$ 800 Duelund), the Jensen Pure Copper Foil Paper Tube is a very nice capacitor (and a nice upgrade from your old Jensen). It just doesn’t make sense to spend US$ 800 capacitors on US$ 500 pre-amp, right? (although some did, like me >.<). And eventually, we have to find option for this “less critical application”, and the option could be this Jensen Pure Copper Foil Paper Tube. If before you love Audio Note or Jensen “classic” Pure Copper Foil and now prefer to choose in between, then you can’t go wrong with this Jensen Pure Copper Foil Paper Tube (US$ 173.9/pairs). It’s a well worth jump from the “classic” Jensen.


No surprise, with around US$ 822/pairs, this should sound special. Compared with Jensen Pure Copper Foil Paper Tube, this Duelund CAST PIO definitely has more resolution and better staging. Compared with VCap, this has better and sweet mid-vocal. Not as revealing as VCap, but the details are there  – without have to be over aggressive. Is it too forgiven character? Not really, since every details are maintained perfectly, not more, not less. Cymbal is cymbal, full with its micro harmonics. If almost all capacitor has its own speciality, whether it’s emphasized on sweet vocal or in high notes, then this Duelund simply has none to be proud of. It’s just maintain the music and all the micro details, included staging and layering. The low is soft, layered, natural. The mid-vocal is just right. The high is very detail, but not sharp or over emphasized. If I have to use words to explain, I would say “Natural”, “Resolution”, and “Pricey” to describe the Duelund CAST PIO.

I think, you can (should) use Duelund if you already have a “near perfect” system. I would suggest a VCap for a “dull” system, a MCap S/G/O to get a live sound (average), and a Jensen “classic” or Paper Tube in a too revealing system. But Duelund? Use it if you already have a “near fine” system, and Duelund will help to add its “perfect touch” on it.

About Duelund’s price tag (which sooooo expensive, the 1 uF/630VDC Silver Foil version sold around US$ 1000 each!), I have to agree with Tempo Electric and I quote them as below:

In an age of $17,000 phono cartridges, $27,000 speaker cables, and $120,000 turntables, he could be right. On the other hand, silver bullion has been selling in the range of 10 Euros (US$13.00) per ounce for years now. How much silver is really in these things, anyway?

If you could afford US$ 9000 CD Player, US$ 10,000 Power Amplifier, or even US$ 5000 for a turntable cartridge and another US$ 20,000 for speakers, why dont you spend US$ 800 for capacitor? Don’t ask me 😉 Sighhh… But still, few hundreds bucks only for a capacitor is considered “insane”…

Added 18 August 2009:

Frederik at Duelund Coherent Audio emailed me and said that Jensen Pure Copper Foil Paper Tube and Duelund CAST PIO are not the same in terms of construction. I completely agree that we (I) never know whether they are the same or not inside (well, no one knows except the manufacturer). But from a standard customer point of view, they both have similar brown/black color tube, same Copper Foil, and same Paper In Oil type capacitor. I think it’s natural if most people would think, perhaps, they both share similar “technique” or “construction” (both from Danish and both “are” Jensen). But from the ears point of view, definitely, they both sound different.

Added 21 August 2009:

Frederik at Duelund Coherent Audio emailed me to clarify the question whether Duelund is made by Jensen. You can read the detail explanation here:

Cooperation with Jensen Capacitors

From time to time, we get the question if a Duelund capacitor is simply a rebranded Jensen capacitor, as is so often seen in the industry. The short answer is “absolutely not!”, whereas the more detailed response is that we do collaborate with Jensen Capacitors, but the products themselves have nothing in common with a standard Jensen capacitor besides being a “wet” capacitor.