The best coupling caps in power amp ?? Mundorf, Infinicap ??

I too just replaced the coupling caps in my 300b Audion with the Jupiter Copper caps and the results were excellent. Very Surprising the improvement.

Rodman,
It's interesting to note that when proponents of the VCap describe its character the word is neutral. 
Duelund CAST proponents descriptive word is natural.  Both are meant to be complimentary yet they convey perceptive differences. Having used both capacitors I understand the chosen terms. Natural is the highest compliment I can use to describe an audio product. 
Charles 

I have built more tube amps that most people have seen.......I have used 20-30 different caps over the years......I have always been interested in the descriptions people give of there sound experience when dealing with different sounds , speakers and delivery of sounds.......I try and use this information in the construction and delivery of tube amplifiers.....I try to understand the descriptions people give for different sound quality in words that differ from one to another when describing the same sound ......When one person says "warm" and they are using a V-cap another may use a totally different word to describe their experience ......autospec

YEP, "variables"!    Semantics, perceptions, systems, aural acuities, references(if any), etc.   Of course, the better(to me, more neutral/transparent/clean/natural/quiet/fast) ANYTHING(tubes/rectifiers/caps/cables/special copper/silver) swapped into the total system, the more obvious strengths OR weaknesses upstream will become.   The natural tendency(for most) would be to attribute whatever perceived differences might be exposed, to the new component(s).       "Best" will always be subjective.   

We've been auditioning coupling capacitors for close to 40 years now. The current king is the V-Cap copper foil Teflon; it is both neutral and extremely musical.

As far as musical goes we've heard some extremely good paper and oil types but the problem we've seen with many of them is that they can develop electrical leakage. Usually this is a very small value, but when you are using the coupling cap in a power amplifier section the effects on the bias on the power tubes should be considered!

For this reason I don't regard such caps as in the running as some power tubes can be quite rare (not to mention some vintage power transformers in some vintage amps) and such parts could shorten the life of both.  So I see the V-Caps as being the only game in town.

Now one important issue with the V-Caps is that being made of Teflon they should be handled as little as possible. For this reason they are shipped in bubble wrap and they really should not be unwrapped until installation. Otherwise the handling will cause them to change value and by this I mean loose value. I don't doubt that this issue alone could be the reason why the well-deserved accolades this part gets are not universal. But that's how it is with Teflon caps.