Duelund cast Pio Hybrid Copper/Silver or Rs series with Silver Bypass PIO

this will be in the signal coupling cap 1uf 630v. 

Ca6bdf8a 14b4 4e97 84e2 fecb0f8ce879zipost
In general, copper has never let me down. I've not gained anything by adding silver/gold to a mix when it comes to capacitors or wires.



I use the Duelund CAST copper capacitors in my Coincident speakers at the tweeter crossover and as output capacitors in my Yamamoto YDA DAC with superb results. I'm thoroughly satisfied with these upgrades. 

From what I have read from those who have done actual listening comparisons the addition of silver seems to improve performance even further yet.  I personally have no direct comparison experience but I don't doubt the impressions of those who do. 
For your use I would stick with the copper CAST. They are wonderful. I am not sure you need to add the bypass silver cap to be honest. Sometimes resolution can be taken too far and long term listenability can suffer. Many recordings are less than perfect 😁

I agree with EriK on the copper Duelund CAST and even the RS as my go to choice. Also, sometimes adding a bypass cap in high voltage electronic applications gives a strange sort of result. Sometimes it can be good and sometimes not as good. Crap shoot and with this kind of money I would not take the risk. Stick with one high quality cap and you may well be better off.

Lastly, don’t discount the Jupiter copper foil cap. I actually like it every bit as much as Duelund copper CAST and they cost far less. Sonic Craft has great prices on these wonderful caps. The Humble Audio site rates the Duelund caps a little higher, but remember these were only tested in low voltage crossover networks, not electronics for coupling. I have compared both in coupling positions and the Jupiter copper foil caps were wonderful. The CAST copper were also wonderful. The Duelund is quieter with a dead silent background. They also had a very slight emphasis in the upper midrange. The Jupiter caps had more air, improved Micro details, and were more even handed through the upper mids. 

Food for thought!

i just want to kindly thanks for all who responded to my questions.    Your advise and input helps alot and will make me understand more about caps, and let me decide which will works best with my application.    Your info are greatly appreciated!


the Jupiter copper/oil wax,  I like the fact that Jupiter doesn't use oil but wax instead.  I find that Oil in cap ( Jenson copper oil) was a bit slow for me.  Here is my dilemma!!  I am trying to find the right cap for my tube cd player.    The design is base on a triode output tubes, the coupling cap calls for a 1.5uf, 450v.   I spoke with the Manufacturer, he recommended that i do not use paper/oil.   

So my question:  Should i stick with the Duelund Rs series or Jupiter copper/wax?? 
Or just ignore his info and buy the top of the line Duelund cast PIO hybrid!  

Hi Zipost,
As I wrote above the Duelund CAST are excellent choices. I also have the Jupiter copper foil capacitors in my Coincident 300b SET amplifier that replaced the Solen capacitors for input coupling . Just as Grannyring wrote, these are excellent as well. The truth is that you simply cannot go wrong with either.

I’m very happy with both. If forced to choose only one I’d give a "slight " edge to the Duelund CAST (such a beautiful and natural midrange and yet without any weaknesses across the audio spectrum). Grannyring would I suspect give that slight edge to the Jupiter 😊. Summary,  you'll be very pleased with either is my belief. 
Curious as to why the builder said avoid PIO caps? Yes the Jensen caps are warm and a tad slow, but nice overall. Not all PIO caps sound the same however. If you love speed, resolution and air, then go for CAST hybrid! If that is what you are shooting for you will get it with the hybrid from Duelund.

I have compared Jupiter copper foil directly to Duelund copper CAST only. I compared in the same gear and in the same position so I have a good handle on the sonic differences. I did this in a tube dac, tube preamp, and tube amp coupling positions. My comments in the previous post should help you decide.

If money is no object and you want ultimate resolution, speed, detail, air etc... then the Hybrid is your best choice. All Duelund caps have this in common as well as a dead quiet background. They, like all PIO style caps, sound very real and less plastic or artificial. The Jupiter caps share this real sound and avoid sounding electronic. Duelund caps sound a tad richer then Jupiter. But I must point this fact out. Duelund CAST copper caps do highlight the upper mids and that in the end forced me to go for the Jupiters which sounded more even handed throughout the sound spectrum. My ears are very sensitive to upper mids due to my tinnitus. Some will prefer this upper mids presence and you must know your preferences. On good to great recordings the slight emphasis on the upper mids is a nice thing. However on less quality recordings it can become a tad irritating. Also, what kind of music you listen too is also important. 
I made up my mind, I will be placing an order for the Duelund cast at PartsConnexion. My questions here is that they make so much series, just mindboggling.

Duelund cast Pio Tinned Copper series
Duelund cast PIO CU Copper series
Duelund cast PIO copper/silver Cu/Ag Hybrid
Duelund cast PIO Ag silver series

Tinned Copper series vs copper series... what difference does this make by adding tin? So much good stuff to choose from. Please advise??

I did more digging/researching into the Duelund Series:

Duelund Cast Copper/Silver Hybrid =VSF cast series + Bypass cap .01 PIO silver series put together in one cap.

if that is the case:

Then the RS series + a Bypass cap .01 PIO silver series be cheaper in price or equal in proformance to the Duelund Hybrid series.  What your take on this?  

This is the cap Charles and I used and liked. All you would need with no additional bypass cap. 

Duelund cast PIO CU Copper series

 They  are expensive. Go ahead and email them saying you would like to splurge on these but need help and ask if they could offer you a  15-20% discount. They have for me in the part on these mega expensive caps. 
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I am glad to have found this thread and would like to chime in with a question. I have just learnt to upgrade capacitors. I recently replaced the stock caps with a pair of Audyn True Copper Max caps to my Line Magnetic 518ia and had great result. And I just placed an order this past Friday at PartsConnexion for a couple Jupiter Copper Foil caps for the crossovers. 

Since I read this thread, I wonder if I should replace the Audyn caps with the Jupiter caps in my amp. Can someone please give me your advice?

I thank Zipost for starting the thread and thank all for sharing your experience. 

Happy listening! ... and experimenting :)
I'd say that if you are committed to this region of top tier capacitors then get the CAST copper rather than the tinned copper version.  As Grannyring wrote,  these are the ones we've both have used with exceptional results. 

No reason to replace those wonderful Audyn caps as they are also very, very good! 
Chumsusi....Audyn Max has a beautiful midrange very sexy type of midrange ( i still miss the midrange).   The highs shimmer exceptionally classy.  Bass is neutral, but can be better!    But to me the Copper Max has a very neutral organic type of sound.  Some people might like it other thinks it's a thin sounding cap.  To me i think it's a neutral sounding cap.  

I had great success using Max as a coupling cap for my cd player.   I wish it has the thickness in sound, a little bit more meatier.  I think that has to do with the dielectric/material and type of insulation.   This is where Duelund & Jupiter outclass other type of caps, it makes the Biggest Difference.   This is the reason why i am going to replace it with either the Duelund or Jupiter to get that meatier/thickness sound. 
I found the Jupiter copper cap to have better bass impact compared to Duelund cap as an FYI. Again, I found this to be true in high voltage useage, not crossovers. In terms of thinness, both the Jupiter and Duelund CAST have meat on the bones body for sure. Both have great in this regard. 
PartsConnexion is all out of the Duelund Cast Copper.   I wanted to order a pair but no luck, kind of wish they had more stock.   Anyone or somehow can locate me a pair of the cast copper series 1.0-1.5uf 450v.  Much appreciated!  

I thank you for your inputs. The descriptions are accurate. For now, the Audyn Copper Max caps will stay in my amp for they sound much better than the stock caps and I only have had them a few weeks. I will keep the Jupiter Copper Foil caps on my upgrade list. 

FYI, I placed an order of some Jupiter Copper Foil caps for my speakers at PartsConnexion couple days ago and had 25% discount.

Happy listening!

hificollective in UK carries Duelund, so you might want to check with them. They ship fast, too. I got my caps in one day with expedited shipping and did not pay a lot extra.

Hope you can find what you want there.
I got a chance to buy both the Jupiter Copper Wax & Duelund Rs Series w/ the .01 Silver Bypass. I want to give my feedback in regards to the two caps.

I like to say thanks to Chris at Jupiter for giving me his utmost time answering my questions and letting me purchase the Jupiter Copper/Wax caps.   He was nice enough for a one time courtesy sample price on these caps.

Jupiter Copper Foil Wax Impregnated:

These caps i would estimate has around 100-150 hrs on them.   I notice it got better everytime i start listening to them. I have to say, this is the first time i encounter a cap that has copper impregnated in Wax. Right out of the box i noticed the design, packaging and the look of the cap is amazing ( sturdy and has weight compare to other caps) it shows that they do care when you spend money on these things. The Jupiter Copper Foil is a detail ( shimmers beautifully) has good transient, has airy mids ( very sexy mids) and tight bass.    Bass is much deeper and tighter.   You can't really say anything bad about the cap. But......

Duelund Rs Copper Wax series w/silver bypass:
just the cap without no bypass, it lacks in detail, midrange is exceptable, but suffer on bass (bass is muddy).  If you compare it to the Jupiter Copper Foil it will Not Compete.  It looses in all categories!  But With the silver bypass,  it's exceptionally good.   It brings the cap to another level!! The high seems to be alot better, midrange is beautiful, bass is quite good.  Blackness is the strong point in the Duelund Rs series w/bypass cap and noise level is much lowered. One thing that stands out the most is the realisim and soul, the Duelund to me is exceptionally good in this category.  The sound is extremely thick and meatier compare to the Juipter copper foil.

In all i would pick the Duelund Rs series with Silver bypass for the output coupling on my cd player. One thing that i did not like about the Jupiter cap, it lack the heart and sole ( very analytical). The Jupiter Cap wasn't musical It's very thin sounding cap compare to the Duelund Rs series with .01 silver bypass.

Why not use the silver bypass cap on the better Jupiter foil cap for the best possible combo?
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I’m currently running and generally liking Mundorf SGO coupling caps in my EL34 based amplifier. I’d like to preserve the spatial depth and overall energy in the high frequencies, but build out some weight/texture/tonal color in lower registers.

Would the Duelund CAST Cu/Ag be a good choice? 

I’ve used Jupiter caps, as well as the Audyn True Copper caps to great effect in other projects, so I’m familiar with the contenders. That said, I’ve read that some folks did not favor bypassing coupling caps, which is what the CAST hybrid cap is in effect. Ultimately, I’m looking for a vote of confidence before making such a non-trivial investment.
I have to tell you I do not believe in bypass caps placed on film caps. Yes, on electrolytic caps in the power supply. Usually bypassing perfectly good film caps sounds kind of phasey and odd.

Well, forget everything I just said. Why? Because these new Duelund Silver foil bypass caps are like magic. I added them to a set of .47uf Jupiter foil output caps in my Int amp and simply am overwhelmed with the improvement. My experience, in electronics, is crazy positive with these glorious sliver bypass caps. Glorious.

These would be so special as bypass caps on tweeter and midrange caps in a crossover, the output of Class D amps, coupling positions in tube gear, output on dacs....etc....

Yes, my experience has been so positive.
To clarify, your question on the Duelund hybrid cap relates to my post in that they are made using the Duelund CAST copper cap with a silver foil bypass cap.....the same cap that can be purchased separately now. The cap I posted on above.

So yes I am confident the hybrid Duelund cap would be simply wonderful sounding.
Another approach not often talked about here is using parallel caps. Using larger value (10uF or so) caps, would be interesting to note if any boutique caps sound significantly better. Essentially self-bypassing.


this will be in the signal coupling cap 1uf 630v.

You say it’s a coupling cap in the signal path, not a de-coupling cap.
You should only use one quality cap as a coupling cap.
No bypass caps, as you will smear the sound because of the different behaviour of each cap at the overlap point (frequency).
It’s fine and encouraged to bypass de-coupling caps with smaller ones.

Cheers George
Grannyring...the duelund silver foil .01uf bypass is Amazing.   I think it's one of the best bypass cap that works wonder in any cap.   They make a huge differences in Any cap! 

George.... thanks for the info.

let say if i did use the hybrid duelund 1.0uf 630v for the coupling signal, which is basically a silver foil .01uf cap bypass with the cast copper cap?  So this will not work?  What is the differences between de coupling or coupling?  Can you Please educate me on this? 

De-coupling, usually goes to ground for power supply smoothing.

Coupling caps have the ac music signal going through them, never bypass them, and always best to use one only here, the most highest quality you can afford.

Cheers George
The magic of the Cast caps is undoubtedly in the oil. I’ve used 600v Duelund Cast caps in an amp and I know the beautiful sound they convey until the oil leaks.

Oil leaks is one issue. What about the shelf life of the oil? Does oil degrade over time? Does the Duelund magic deteriorate over time?

V-Cap CuTF and Jupiter Copper caps won’t have those issues and are my preferred caps to use.
Excellent point!  I am with you on this, longevity might be the Biggest issues for the Duelund caps or any other caps that has the oil impregnated in them.   
No worries on the oil. I am not aware of any such issues in real life usage. Oil impregnated caps have been sold for decades.  This would be especially true for crossover usage where there are no heat issues to worry about. 
There are 2 excellent capaciyors I am currently using  in my preamp no direct voupkjng caps it us transformer coupled but has a big Mundorf Supreme 22uf 
Very respectable I added 15% ,the new Duelund Jam  using their latest using a lite tin over Copper which for sure opens up the top a bit in s paper oil, but in a Aluminum housing not quite as fleshed out as the cast but close at half the cost 
Very nice depth and instruments have a nice accurate tonal balance.
On the Dpeskrr end I gave a Huge 68uf  Clarity Csa cap  the Jupiter 2.2 ads some realism and depth  the last cap Brand new Jsntzen Alumen Z is a Aluminum foil with very very thin dialectric very smooth but fadt and detailed grest imaging 
A great match a very easy cap to like blends with most other caps. 
Priced very nice I put in a pr of 4.7uf caps  the Voxativ drivers really come alive 
A new budget favorite cap  they only go to 10uf.  Hifi collective is the only place yo buy , order the FedEx option delivered in 3 business days . 
Both Duelund Jam, and Jantzen  Alumen Z foil  caps  would be a great combo 
The Jsntzen only 100v ,for Loudspeakers. I AM ARE 630v and are tanks a 3.3uf 
85mmx 75mm and over 1 lb each.
Having my speakers upgraded, with the crossovers currently being made up:

  • Tweeter Network - Jupiter Copper Caps (4 x 10µF and 2 x 1µF),
  • Woofer Network - Jupiter VT Round Aluminium Caps (2 x 6.8µF)
  • Main Caps being bypassed with Duelund Silver Caps (0.01µF)
  • Resistors - PathAudio 10W
  • 10awg hand wound Air Core Inductors
The crossover board is getting a wee bit tight, especially with the main Caps (they’re actually slightly bigger than a Coke can). Not quite finished yet, still need a couple of resistors for the Shunt, and then attach the ribbon wiring, but nearly there :)

Very nice.  You have some very high quality boards that will help make your speaker sound beautiful. Did you make the inductors or were they made for you? Nice! 

Mike Lenehan (Lenehan Audio) is doing the upgrade from my ML3 Ref’s to the newer ML5 Ref’s (they’re his speaker brand). Not so many people in the USA have his speakers, but here in Australian he’s very well known for his own brand, and has a very loyal band of customers (me being one).

His standard ML5’s come with Jantzen Superior caps, with Duelund carbon resistors, but he’ll upgrade what others want (based on his recommendations). A lot of people are gong for Duelund VSF’s, but I went for the Jupiter Copper as been told they have a bit more ’flavour’ to them over the VSF, and as Mike’s speakers tend to be very neutral/clean/precise (or whatever others want to call it, maybe resolved is a better word) I’ve went for the Jupiter Cu. The Woofer network wouldn’t give back the full value of using Jupiter Cu’s, therefore have went for the VT rounds in here.

Lots of people have been writing about the benefits of the Duelund Silver bypass Caps so I’ve included these in both the Tweeter & Woofer Networks. Realise most would say it’s not worth it in the Woofer network, but as my current ML3’s have to be shipped to the other side of Australia and back for the upgrade (I live in Perth, Mike lives in Queensland) I thought it worth including for the small(ish) cost to add.

The inductors are hand wound by Mike (and his sons, who also help in the business), and he prefers these (also helps with the cost). Some people are going with Jantzen Wax Foil inductors, but Mike suggested I stick with hsi hand wound one’s. I’m not much of a numbers guy when it comes all the componenets, etc. but he said the 10awg produce 1.25mh DCR 0.09ohms (he may even have improved on this, I’m not sure).

I’m also changing the tweeters, currently 30mm Wavecore TW030WA14, but changing over to SEAS Exotic T35’s. Not my shout, but Mike and others feel it’s a worthwhile upgrade (a few people like the benefits of the Alnico magnet)

I’m just a customer who pays the bills to the guy who knows what he’s doing - Mike. He’s not a salesman, but a speaker builder who has pride in his work, and as such will put everything into his speakers (at a cost) to make them the best sounding he can (within the budget).


My current speakers:

You made a good decision sticking with the heavy gauge solid core  wound over foil. You will love the results.  What are you using for internal wire. Looks like Duelund copper stranded? Thoughts of placing the crossover outboard? Very good for Sonics. 
 Nice  looking speakers. Look to have great build quality.  

The New Duelund Tinned Copper,paper in oil  .1uf bypass caps are Excellent 
The New Tinned Copper which their new Jam caps have which I have in my preamp are truly excellent they have a aluminum case ,not quite as good as the top paper case.  The Tinned  Copper bypass cap I just got  .my brother and his friend say these little caps truly add depth,as well as air to loudspeakers.
They also have a Silver paper in oil , a little better detail ,then the Copper bypass 
But not as much body. And at 600volt  can be used anywhere.
I have Altec 604E speakers with Werner Jagusch crossover. I bypassed high frequency driver's part of "original" WJ crossover vintage capacitor with Duelund Tinned Copper Foil & Wax/Oil BYPASS capacitor. Sound improved a lot. It sounds like new, much more expensive speakers!
I'm thinking about buying Duelund RS capacitor.
What do you think, will Duelund RS capacitor bypassed by Duelund Tinned Copper Foil & Wax/Oil BYPASS capacitor significantly outperform "original" WJ crossover vintage capacitor bypassed by the same Duelund Tinned Copper Foil & Wax/Oil BYPASS.
Yes it will. Jupiter copper foil will be even better with that wonderful Duelund bypass cap.  
Hi grannyring,

Do you think Jupiter will work better with compression horn driver then Duelund RS?
I mostly listen jazz and classical. I rarely listen rock. I don't listen "junk" electronic and dancing music at all. 
I have 300B SET DIY amplifier (6SN7-6F6-300B).

I certainly do think so.  I have compared the Duelund CAST to the Jupiter and I actually like the Jupiter even more. It is a wonderful sounding cap.  
I bought Duelund RS for high frequency part of my crossover.
I did some burn-in using Frybaby2.
I like results. Sound is unbelievable transparent! Now my Altec 604 can be compared in this regard to Lowther based speakers.
I have second order LP filter for mid-base driver of Altec 604.

Will changing of capacitor in 2nd order LPF do the same huge effect?
I need 8uF capacitor. Will Jupiter VT Series capacitors good a match for LPF for my Altecs?
Jupiter caps are excellent and are the best "bang for your buck" brand. The Flatstacked series which I'm familiar with has a natural tonality and open soundstage. 

I would not think the Rs is comparable with the Jupiter copper series.   The cast duelund to me sounds better than the jupiter copper series.   Has more organic, lively and romantic sounding.  
So which one sounds better in the crossover - Jupiter Cu or Duelund RS?

I have seen little mention of the VH Audio Copper- Teflon caps I have been using 
these and for resolution none better ,but take up to 4-500 hours runin time.they are flighty warm ,but not much speed and resolution
for a bit more air  and  depth the Duelunds are vest 
They are nice, but not my particular cup of tea. Just a tad too thin sounding vs Juputer or Duelund CAST. 
grannyring do you know the Morel ET338? What do you think which capacitor is the best for this tweeter?