Crossover Capacitors for Accuton Tweeters - Solen -> ClarityCap -> Jupiter -> Duelund


I've got Coincident Pure Reference Extremes with an Accuton ceramic tweeter and have moved through four different capacitors to provide my high pass filtering.  The speakers only have one 4.7uF capacitor in the crossover (no resistors or other components), so it was pretty easy to hear the sound of each cap. 

Started with stock Solen's, then tried Clarity Cap CMR, then Jupiter Copper Foil & Wax, and finally Duelund Tinned Copper CAST.  Just installed the Duelunds on Monday and despite not being broken in, they sound absolutely amazing.  Smooth, sweet, and detailed without any grain or harshness.  Just really spectacular, they let me hear more details while also preventing the tweeters from being aggressive, which has been a problem I've had to work hard on ever since owning the speakers.  

To comment lightly about the other caps I heard, I actually thought the stock Solens were pretty good.  They had a nice sense of color... when I changed out to the clarity cap, things got a little clearer, but felt too neutral.  I read that they are "ruler flat" and found that a good description.  I liked the cleanness, but missed some of the tone & color from the Solens... felt like I got a good combination of those two traits when upgrading to the Jupiter Copper Foils.  After about 6 months of the Jupiters I finally bought the Duelunds as a self-birthday present, and they completely lived up to my (very high) expectations.  Just beautiful, organic music.  Can't wait to see where they go over the next 200 hours.  Only have 10 to 20 on them so far.  

If you've got an accuton tweeter and can handle the stupid cost (and size), I concur with everyone else's recommendations (thanks humblehifi, jeff's place, @charles1dad, & @grannyring), they will make your speakers sound better.
128x128cal3713

Well, no capacitor is certainly better than the most expensive, highest-quality option you could buy, assuming the tweeter is built to handle a full range signal!  Congrats.

Thanks for the input!

I've been looking into caps. Duelund CAST were quoted over $2k...hahaha. Looked into ClarityCaps, V-Caps, and was getting to about $150-250 per cap, while the replacement AMT diaphragm is $130. So I have removed the protection cap and I'm driving the AMT directly from the 45-type SET. So far no issues. It sounds much better than with the cheap caps I had. Pretty impressive actually.

I am getting a replacement diaphragm just in case, but no cap sounds pretty amazing. Should I have trouble I will need to revisit the decision. Maybe tomorrow, maybe never :-)

@lewinskih01 Maybe a Mundorf in the EVO Supreme line?  They've got your large value caps and I really enjoyed the Supreme Silver Gold Oils in my linestage as output capacitors.  The only thing I didn't like was that they impacted bass performance... but everything else was just spectacularly beautiful.  Clean, quite, and rich sounding with just spectacular 3 dimensionality.  Clearly you don't have to worry about bass performance in this usage scenario.

And Mundorf has a lot of other cheaper options at that value in the film & oil lines if you want to start small and see what happens.

Posting in this thread since so many experienced with different capacitor brands have contributed.

What are the better brands and products for 25-30uF caps to use in series with AMT tweeters? Duelund CAST and Jupiter's seem to come in smaller values only. 

Thank you!

Interesting. I have been using my diy sit3 for a couple weeks and just switched back to the f4s. I lose a little bass energy, but gain warmth and smoothness. Still not totally sure which I prefer, but the F4 is just a fabulous amp if you've got the right speakers.  What are you driving with them?
Cal3713; 
To bring this back to discussion: 
I have XA25 and SIT3. The F4 is hands down a level above all of these. I have in fact a F4 in Mono configuration and its superior to SIT3 in so many ways.


Bill (brownsfan)I  agree with you. This IMO was a language/communication issue.  I realized this after reading Raul's 2nd clarifying post on this thread.

Charles

@rauliruegas 
"our hobby is all about MUSIC."
Exactly!  
I suspect if we sat together in a room listening to a piece of music we would have similar reactions to what we heard.  I think that most of what remains between us is due to language differences, not differences in substance.  
Enjoy the music!
Dear @brownsfan  : I agree with almost all your post that's not " against " mine. What happened ( I think. ) is that due that english language is not my native language many times I can't explain things as need it.

Yes, not all distortions are really bad ones and exist every where including in live events.

I was aware about J.Hendrix but not Page. Yes I was aware too on N.Pass designs  whom and due that several high end customers were/are accustomed to tube electronics he choosed for something that can give a quasi-tube signature, that's was too why when in Threshold always used bipolar transistors in Pass he choosed FET/Mosfets.

Yes, it's true that through age always exist a degradation on the sound perceived sensitivity but we have to remember that we hear/listen trhough whole body not only the ears and that the brain knows and develops those harmonics that for whatever reason were not " listened ".

Yes, final arbither must be our " body ".

Don't worry about distortions ?, well I try to to take actions in my room/systems to put at minimum. I know that today I'm enjoying my listening sessions better that 5 or 10 years ago and I'm sure that you are enjoying the same as many other gentlemans.

All of us are growing up " day by day " as our room/system too. Our hobby is all about MUSIC.

Btw, I agree with @racamuti  statement on those distortions:

"""  Yes but, I don't want to add additional distortions to Jim or Jimmy's guitar just the ones they add. """

because we have to add to the distortion developed through the recording proccess and our system play process.

R.


Yes but, I don't want to add additional distortions to Jim or Jimmy's guitar just the ones they add.

TISH
@rauliruegas I may not be following your line of reasoning correctly.  If I am missing your point, I apologize.   Consider the music of Jimi Hendrix and Jimmy Page.   These two individuals, by almost unanimous consent, are two of the greatest guitarists of all time.  It is my understanding that they both deliberately introduced distortion into their guitar work.  It was a part of their creative expression.  Distortion was/is an integral part of their art, and without it, the music cannot convey the intended message.  Or consider Nelson Pass, who developed a 2nd harmonic distortion generator for those who wanted to introduce a bit of SET flavor into their solid state system.  My point is that not all distortion is subjectively objectionable.   My previous mention of the great violinist Isaac Stern delivering a live performance that emulated the death cry of a tortured cat, which I hope never to hear the like of again, provides an example where a perfectly undistorted absolute reference recording would not be subjectively desirable.  

Recently, someone mentioned that it is generally not good for a listening room to be ruler flat.  Rooms that don't have a bit of high frequency roll off can be perceived as too bright.  Consider another scenario.  Typically, one's ability to hear the highest frequencies is diminished as one ages.  For such an individual, might it not be advantageous for such a person to have a system or room that provides an offset for that hearing loss?

I'm not saying there is no value in measuring a room's frequency response and decay times.   Those measurements can most certainly be a guide as one attempts to optimize a room.  But the final arbiter must be one's ears.   I'm not saying there is no value in taking objective measurements of hardware.  Those measurements can be invaluable in assembling a system that works well together.  But the measurements cannot tell you how a particular piece will sound.  Again, the ear must be the final arbiter. 

Most of the folks around here are well informed listeners.  They frequent live venues and have a pretty good idea what a recording of acoustic music should sound like.  They also know when a system, a system component, and yes, a particular capacitor delivers that special level of engagement, which may well not measure as well as another choice that may objectively measure better.  

Enjoy the music indeed.  Don't worry about the distortions until your ears or your emotions tell you that you need to worry. 



Dear @brownsfan  : """  What is wrong with enjoying distortions? """

in reality are not the distortion it self but the kind of those distortions and its higher or lower levels.

Distortions levels is what defines/makes differences in the quality level performance of any room/audio system.

All room/audio systems have inherent distortion levels, so always exist trade-offs and in each one of us systems we already choosed our self " best " trade-offs that put us nearer to our targets. Nothing is perfect.

"""  those venues with which I have experience don't even deliver a consistent voice  ""

agree. Everything in a venue could change each one of us perceptions of what we are listening, even attended in the same seat position. Things are that the  people that attend to the venue  the same day as us is not not only exactly the same number/popullation but their seated distribution is not always the same and certainly not always people go with the same kind/fabric of clothes and all those has influence in what we listening there. But even musician/players are not seated exactly the same each session after sessions and many times they don't have the same day by day " mood "
. Even room temperature could be not the same and temperature has its own influence in the instruments voice.
Normally the venues has an overall "signature "  that depending on those and other surrounded characteristics shows some kind of little " deviations " from the overall venue signature.

How can we enjoy MUSIC and not DISTORTIONS?  well we can't avoid several kind of room/system distortions and the best we can approach is to put at minimum those distortions and to achieve that we have to be aware/identify those distortions and this is extremely difficult and as difficult too is to be sure from where is developed that distortion.

Nothing is easy in audio when we are looking for " heaven " and this is what makes audio so interesting other that ENJOY THE MUSIC.

R.


This thread took an interesting turn... always good to hear everyone's opinions.
Hi Bill,
I like your "rants" they’re grounded in logic and stimulate thought. Given the gist of Raul’s 2nd post I believe he’d agree with you. No room, system or component is without fault and we as listeners choose and live with our accepted/inevitable compromises. A couple of years ago I heard jazz trumpeter Roy Hargrove perform at a local jazz club. My table was at the very front of the stage. I could have reached out and touched his horn. While playing some ballads with his fugelhorn the tone was  utterly full, warm and saturated with beautiful richness. Just sheer beauty. This is what I hear, I can’t speak for what others may hear. In my humble opinion many components strip away this very real warmth and harmonic richness in the chase for so called accuracy and detail.

A live vibraphone, tenor saxophone or cello for example are just undeniably rich and tull of color and richness in my live listening experiences. It seems in current High End audio these qualities are to be shunned and have taken on a negative connotation. This mindset doesn’t work for me. For me a good 300b amp doesn’t add color, it preserves it.
Charles
"enjoy the MUSIC NOT DISTORTIONS."  Friends, Raul has said a lot with that statement.  

Forgive me, but I've been down an epistemological rabbit hole for the last couple of years with respect to in home reproduction of music.    So I am going to challenge what might seem like an indisputable maxim.   Now mind you, I replaced my dearly beloved 300B Frankensteins with my equally beloved Atma-Sphere M-60's, precisely because the Franks, in my system and room, were driven to OBJECTIONABLE levels of distortion.  It would seem clear, would it not, that I would accept Raul's premise?  Sorry.  I have to ask, "What is wrong with enjoying distortions?"   If a 300B amp delivers an engaging listening experience with 3-4% 2nd harmonic distortion, so what?   What is wrong with that?  Does a 300B with all of its glorious midrange bloom deliver a typical live venue experience?  I would answer that question no, but clearly others would answer that with an emphatic yes!  I don't frequent the same venues as Charles, and those venues with which I have experience don't even deliver a consistent voice.  Charles isn't objectively wrong or right to prefer his Franks over other amps he has tried.  Cal3713 isn't objectively wrong or right to prefer the Duelunds over something else.   The have gotten what they sought from the choices they made.  That means they made good choices.

I'm not so sure that accurate reproduction of a live venue is even the desirable target.  I once heard Isaac Stern performing a work in a venue that was dead.  Somehow, he managed to emulate the death cry of a tortured cat with his violin.   I would not be interested in reproducing that performance in my listening room. 

We all listen critically to music for a reason, but I suspect we do not all listen to music for the same reason.  In fact, I as an individual listener don't always listen for the same reason.  Sometimes, I want Beethoven.  Sometimes I want Chopin or Schubert.  Sometimes, most of the time actually, I want Bach.  Why?  I won't take the time to provide the answer.  If you know the music, you understand my point. 

There is a place for first principle knowledge, and there is a place for experientially (or experimentally) gained knowledge, and there are different types of experiential knowledge.   Those who achieve their goals have usually done so by balancing the science and the esthetic elements. 

Sorry for the rant.  Too much intolerance of intellectual diversity has become the norm.  
Hello Raul,
I appreciate your last post and the clarification of your stance. I do not disagree with anything that you have just written. My only point was This topic/area is by default purely subjective. Each one of us will pursue what we think sounds right/best based on our respective perspectives.

Sweet and smooth is  not part of your music listening vocabulary and I can respect that as it is simply based on “Your” Live music listening experiences. Ironically sweet and smooth are characteristics I immediately notice in the presence of live musicians playing un-amplified instruments. As you note it's quite possible that these terms have different connotations to us individually. 

You and I are just an example of two music lovers with extensive exposure to live music who perceive things differently. I appreciate your contributions to this site.
Sincerely,
Charles
Dear @charles1dad  : I'm not saying I'm just rigth because if our reference is live MUSIC then no one can be rigth in any room/system combination no matters what.

I know I'm away from that target and I know too that every single link in the roo/system chain has its own distortions and colorations.
Diastortions/colorations that goes according each one priorities.

Each one of us fine tune our room/system according to those priorities that at the end is what we like it but several of our room/systems has its own limitations, limitations that preclude to really stay " there ".
Always exist beterr electronics or cables or speakers or whatever and no one of us already listening all the options out there so the best we can do is try to do our best effort to stay nearer to our targets.

Duelund's through my speaker tweeters just does not performs as I expected and where the Alumen and Mundorf makes a better job.

The Jantzen Alumen is extremely humble cap against the Duelund/Jupiter/Mundorf and many others and it's not Cu. Talking with Jantzen people told me that in this second part of 2019 they will have the Cu version and certainly I'm waiting for after the good results I achieved with this non Cu Alumen version.

Sweet or smooth characteristics are not in my MUSIC vocabulary, maybe at low SPLs but not at 87db-92db SPL at seat position and certainly in a live event seated at near field listening ( 92db-105dbs+! ).

In the other side same audiophile words has not the same meaning for each one of us and maybe could be an explanation of some of my comments.

Btw, I don't try to say that I'm rigth and he or " you " are wrong. Just different ways to " see the life ".

I'm not try to be condecendent with any one and agree with @cal3713  in his statement:

"""  Definitely it's a journey trying to get them to where I think they can go.  ""

Dear @grannyring  unfortunatelly for all of us our room/systems are different and certainly with different room/system whole signature. As @cal3713  and you and other gentlemans I'm where I like to stay where I enjoy the better my listening sessions and this is the must important fact for each one of us.
At the end my opinion is only that: just another opinion with no single attitude to fend any one or diminish anything at all.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
Erik,
I agree with your statement about "added sparkle" not heard in the presence of live instruments. I became aware of this effect from personal experience many years ago and realized that so called hyper detail is simply added upper frequency tilting or emphasis. I’m not knocking those who prefer that type of presentation (individuality must be factored in). Personally I do not hear this emphasis (however other listeners may )  even when in close proximity to live music performances. You final sentence sums it up nicely.
Charles
Hey @railruegas,
You made some interesting points which made me think more of room acoustics and volume.


How loudly we can play music in the home, compared to live, as well as the treatment, or lack thereof, has a lot to do with how a speaker is tuned.  Speakers with a built in U shaped curve can sound a lot closer to live at lower volumes. Rooms with better acoustics also can sound more intimate.  I often suggest people listen to their speakers 1 meter away. The difference between that and the couch is room acoustics. 

Users can adjust this with loudness switches, room acoustics and the like.

I don't find top end Mundorf's to be more like live music so much as adding sparkle which I just don't hear in real life. It's like a scintillation, kind of like a ribbon tweeter. Many ribbons have been shown to add some harmonics and that's kind of what I hear.


As you say though, you really need to make your own choices and buy what you like.

Best,

E

@charles1dad Also, I did compare a FW SIT2 (from reno) and the Franks back when I was buying an amplifier for the Super Eclipse IIIs.  I preferred the Franks as well.  I'm sure if the PREs were an easier load I'd never have moved on.  
@brownsfan Me too.  If not trying to find a booster amp to augment the Franks I wouldn't have ever tried the F4.  In the end, I just think it's a case of a particular design working well for a particular speaker. 

Of course there is this quote from Nelson in the manual:  "The combination of a simple Class A circuit operated without feedback and the good objective performance gives us a superb sounding amplifier. The low distortion, bandwidth extension, and high damping results in midrange clarity, treble detail, and control on the bottom end. While these are available from most good solid state amplifiers, the F4 also brings depth, imaging, midrange warmth and top-end sweetness. Overall, it is one of the best sounding amplifiers, and if you can live with unity voltage gain in your amplifier, it is possibly your best choice."
Bill (brownsfan),
I had the pleasure of using a professionally built Nelson Pass D.I.Y. designed S.I,T 2 push pull version that is 40 watts per channel for about 3 weeks (thanks to a generous Audiogon member loan). I can tell you it was a ’VERY’ good sounding amplifier without question. It is a solid state amplifier I could happily live with.

Quite competitive with the Frankenstein in many ways. Both are very open and transparent. Ultimately I preferred the Frankenstein as it was a bit more tactile, 3 dimensional and had just a bit more tonal/harmonic fullness/richness. More humanity if you know what I mean.   But again the PP S.I.T. 2 was excellent. Your speakers require a little more power and current than my speakers so I believe that they’d be a good match for you.

I certainly can’t say you’d choose them over your Atma-sphere amps but I think you’d find them legitimate competitors.
Charles
@cal3713 , thanks for the update on your journey through the amplifier jungle.  Pretty fascinating stuff.  I am a little surprised that the F4 clones ended up on the top of the heap.   I've had an itch to try one of the Pass or First Watt amps myself, and I think I would also enjoy the diy experience.  @grannyring may have created a monster by holding my hand through the rebuild of my Super Victory II crossovers.  Please keep us informed after you have a chance to evaluate the SITs vs the F4s.  
Rodman99999,
Very well stated. For Raul to suggest that his system/approach gets it right and cal3713's results  are merely pleasant distortion and coloration is the height of arrogance and condescension. 
Charles 
Ever notice: whenever you’ve found a component(passive or active), tweak, room treatment, cable, or ANYTHING that enhances your musical pleasure, or- provides an experience that brings you closer to the original recorded event(even if YOU did the recording), there’s always someone out there(especially, in here), that’s never seen or heard your system, never been near your listening environment, or(in all likelihood) any of the music venues you’ve visited(certainly: not the same seating, whether audience or sound booth), that just HAS to assert, "THAT CAN’T BE RIGHT"? It MUST be some type of distortion/coloration! YOUR system CAN’T provide as much as a simulacrum, of actual live music(regardless of how familiar YOU might be, with the real thing)! It CAN’T POSSIBLY be enjoyed at realistic SPLs(regardless of whether acoustic or reinforced originally, how long you’ve been involved in music as a profession, or- what comprises your system/room acoustics)! AND: YOU’RE JUST WRONG(irrespective of how many others have drawn the same conclusion, or- experienced the same effects/results, as you)! You know the type and their songs(AudiogoN’s Top Hits): "If yours does it and mine doesn’t; yours is wrong(or-it’s distortion)!" "If you can hear it and I can’t; it’s your imagination!" "If it works for you, but- I haven’t TRIED it, can’t HEAR it, or- it didn’t work in MY home; it’s Snake Oil!" Enjoy the music / PAN THE BS!
@rauliruegas I've been a scientist for most of my adult life and certainly am biased towards truth. That said, if I could listen to every speaker/amp/source combination out there I'd probably choose the one that made the greatest percentage of my music "sound good", accuracy be damned. I don' know that system would include the Coincident PRE's though. They are intensely revealing.  I'm glad I have them though, because they don't cover up anything and it's allowed me to learn a lot about music reproduction. Definitely it's a journey trying to get them to where I think they can go.
@charles1dad when I had the super eclipses, I never had any indication that the Frank's were straining in any way. Bass wise, I certainly had more out of that combination than I've been able to extract out of the PRE's. In part I upgraded because of the seduction of better sound, but I also moved and started pushing the SEs harder than they should. My living room is 19 x 16 with 23 ceilings and the 16 is fully open to the attached dining room, that's a 25' run to the front of the room.  The PREs are certainly capable of much more than the SEIIIs, but I'll always love the way the Frank's played music on the SEs.

Cal3713,

Your speakers are a tougher load than my Coincident Total Eclipse II so I can understand the need for a better matching power amplifier. The Frankenstein has been ideal for my needs. Given your teriffic results with the First Watt F4s I suspect you'll love the S.I.T.3 mono blocks.

Charles

Very interesting comments regarding listening preferences. Truth is they will differ
with each individual. I can tell you I’ve listened to live unamplified music in small intimate jazz venues (2 feet from the stage sometimes) and peformances in private homes (very up close at times) for many happy years. When I use to practice with my trumpet (can’t get  any closer than that) my ears have just become accustomed to the sound of live acoustic instruments.

I find myself in agreement with grannyring in thaat the Duelund is hardly colored. In fact what so strongly attracted me to it’s performance is just how dynamic, natural and realistic it captured the pure tone, vitality and harmonics of acoustic instruments so convincingly. I understand we all hear and interpret sound in our own unique ways. The Duelund CAST is outstanding in my opinion. Jupiter copper foil are excellent but I like the Duelund even more.

One man’s natural/organic is another man’s colored.

One man’s neutral is another man’s analytical/sterile.

Absolutes in regard to sound quality and perception don’t exist.

Charles

The Duelund caps in question are not colored based on my listening and testing. I would also say the Jupiter copper foil caps are not colored. Both are even handed top to bottom and do not exaggerate any part of the frequency spectrum. I have used the Alumen caps and currently have them in my Dali Epicon 6 speakers as part of an upgrade I did. I like these caps as you do. However, they are not more neutral than the Duelund tinned copper or Jupiter, but they are flatter sounding and less dimensional sounding. I wanted to place the Duelund tinned copper CAST in my Dali speakers, but it is simply too costly for me right now. The Alumen Caps are one of favorites in terms of value. I like them more than Mundorfs which to my ears are tipped up in the presence area and not as natural or neutral.

I do not hear a warm or romantic editorializing with the Duelund or Jupiter caps. They offer improved realism over Alumen with instruments, voice and venue sounding as they do ...... not a facsimile or colored rendition. They sound so much more real! Recordings sound unique and fresh with no sense whatsoever that the cap is imparting a sound character of its own to each recording. I have not heard this sort of editorializing in my builds or mods for myself and customers.

Perhaps what you hear as distortions or editorializing is actually the tonal nuances and completeness of the instruments’ sound being fully revealed with the Duelund CAST tinned copper cap? 
Dear @cal3713 : Great speakers you own, very good overall design and hard to beat.

Many of us almost always " want " better quality performance levels in our room/systems and many times through different room/systems changes " up-grades " we think we achieved that " better " whole target and normally what we got was more than a better quality levels a " different " quality levels but not necessary better one. We try to achieve what we like that not necessary means is rigth.

As you I tested several caps in my speakers and made comparisons through the tweeters caps: 4.7 uf. Mundorf, Jupiter, Duelund, Jantzen, etc.

My MUSIC/sound prioriites/targets are different from yours. My main target is to stay truer to the recording and performance must be in the neutral side with the natural MUSIC color, very good tonal balance, efortless dynamics/power, fast transient and ryhthm and with the natural agresiveness of the live MUSIC event seated at near field position that’s where normally the recording microphones are " seated " ( 2-3m. ).
Live MUSIC means too the SPLs of live MUSIC event, way higher of what we are accustom too at home.


""" Smooth, sweet, and detailed without any grain or harshness. ........ preventing the tweeters from being aggressive, which has been a problem ...."""

""" Just beautiful, organic music . """

Well live MUSIC at near field position is everything we want but " smooth, sweet or organic "" and it’s agressive, brigth and sometimes with harshness. All these is live MUSIC that's my reference.

I’m not questioning what you like because our different targets.

The designer of your speakers choosed Mundorf caps for its neutral characteristic in that frequency range where according my targets it has when several audiophiles look the Mundorf’s in the brigth side when it’s not when compared with live MUSIC seated at nearfield position.

What you like is something that several audiophiles are accustom to where the performance quality is more or less like if we were seated at 20m-30m from the live source/instruments. Nothing wrong with that but it’s not my target.

At the end I choosed the Jantzen Alumen over the Mundorf and I choosed because has better tonal balance. No, it’s not so expensive as the Jupiter or Duelend but these caps are heavy colored, are not neutral as many people could think.

Always is more easy to like something colored than dead neutral.

Anyway, good that you are enjoying your system and this fact is the more important for you.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.


Not sure if this (google photos) link will work, but here's a picture of the Duelund cap next to the Jupiter and original Solen, in case folks are curious about size:  https://photos.app.goo.gl/XRieYxBEng4nH4tFA
@brownsfan As you know, the Franks struggled a bit with the load of the PREs.

To recap, I tried a Lyngdorf 3400, Atma-Sphere M60s, and a Pass Labs XA25, but in each case settled on the Franks despite their poor bass performance.  Eventually I decided to built a pair of DIY First Watt F4s.  They provide only current gain and my plan was to use them as a booster amp to power the PREs' bass units while being driven directly by the speaker outputs of the Franks.  Unfortunately, bi-amping just killed the speakers' coherency.  That was also true when I had tried using the active crossover of the Lyngdorf.

Surprisingly, when I tried the F4s as the sole amplifier of the PREs, they actually beat out the Franks and are my favorite amplifiers of the above list.  They retained a great deal of the sweetness of the Franks, improved the bass, improved clarity, & reduced distortion.  Soundstaging is roughly equal... maybe a very slight loss of front to back layering.  And maybe a small reduction in tonal color.  After having them in the system for a month, I put the Franks back in and it was clear that there was no going back.  Just finished selling them and all the upgraded tubes (separately because no one would bite on the full package) this week...  

It's also nice to have built my own amplifier.  Way cheaper (<$1800 for two F4s) and fun to learn about the circuits and parts.  Plus the Pass group at diyaudio is fun to interact with.  Instant technical service when something goes wrong, and people sent me free parts to help after I toasted a MOSFET because of inexperience.  I found the process a bit addicting actually.  Just ordered the parts to build a pair of DIY SIT-3s.  They use the same power supply and chassis as the F4s, so you just have to swap out a circuit board and you can try out a completely new amp.  Couldn't help myself despite my satisfaction.
Cal7313, I am most happy for you! I realize it is risky to spend big money on a part that you were not 100% sure would deliver the sonic goods you hoped for and expected. Turned out to be a great investment in your enjoyment of music. Good for you!
The new Duelund tinned copper CAST caps are easily the finest sounding capacitor I have heard. They are fantastic and to my ear significantly better than the standard CAST Duelund Capacitor and Jupiter copper foils.  However, they are so darn expensive. I use them and the .01 uf bypass capacitors regularly now. They bring you closer to the emotion and feeling of the music.

I am also a big fan of the Duelund tinned and stranded copper wire in cotton. To my ear they sound as beautiful as the capacitors. Using this wire for speaker cables, ICs, DC power supplies, Internal speaker wire etc...has been a revelation. Great products from Duelund.

I placed the Duelund tinned copper caps and wire inside my Lyngdorf 2170 and smiled so big with the result. Just so engaging and beautiful sonically. Music flows in a way that causes you to just melt away into the music

I have one other recommendation that is cut from the same sonic cloth. Use the Perfect Path Audio Total Contact paste over all your solder connections and part lead outs for another significant jump in musical bliss. Enjoy!
I’ve had Duelund’s Cast PIO/Cu, as coupling caps in my Cary monoblocks, for the past few years and loving the presentation/realism. Guess I’ll now have to try their Cast-Cu(Sn) Loudspeaker caps, in my Emerald Physics speakers. Thanks, pal.

Hi cal3713,

I’m happy to read of your very fine outcome with the Duelund  CAST copper foil capacitors.I have always felt comfortable recommending these superb products. I have them in my speakers and DAC and they improved what were already excellent sounding components. Just as you described, beautifully natural, organic and alive.Worth every penny in my opinion.

Charles

@cal3713, I am happy to hear you found the right cap for your PREs.  Having had the pleasure of a long audition of the PREs, I can well imagine that the Accutons could be a bit on the aggressive side depending on other system components, the room, etc.  BTW, are you still driving them with Franks?