Resonance
It is common thought at least on this thread that the best of today's capacitors exceed what was available in the past.
It has been known for decades that bigger beefier caps were more dynamic and were in many companies better amps.
What is better today? Resonance or better control of it. What is bad about resonance? Resonance fills out a frequency giving perceived liquidity. (sounds good) The bad part is this is not done across the spectrum but at the frequency the part resonates at...
In all the cap testing I have done it is the middle upper to upper frequency that parts resonate with loss of clarity and detail at the extremes.
Tubes. Vintage capacitors do not have the same following or held in the same regard as vintage tubes. It seems no tube can be as good as a tube made many years ago in North America or Europe from the "tube era"...
Here is a review not of a capacitor but of a new tube (Northern Electric) vs. vintage. (KT88's)
The reviewer does not know it (I think) but is talking about resonance. I feel I could have wrote this comparing vintage caps to Duelund CAST.
"Compared to a pair of NOS tubes that I had on hand, the only area where the NOS tubes excelled was in imparting a noticeable liquid quality to upper mid-range and lower treble. However, this small gain was at the expense of considerable bass control, definition and detail, especially given the single-ended application in which these tubes were used. While the NOS tubes imparted a romanticized character to the sound, the NE tubes conveyed a confidence that the listener was hearing more of the source material and with greater accuracy".
Tomorrow I am going to test the vintage 12AX7's tubes vs. the new Gold Lions.
Selection of tubes is an extensive list of Telefunken, U.S. and British made tubes.
Even before the test I was quite shocked when the Gold Lions went in. They exhibited all the same characteristics of putting in CAST caps...
Low resonance increased detail I had not heard more and better controlled bass.
Looking forward to trying some of today's better tubes.