The difference between Duelund CAST and Jupiter copper is this. I have used both in crossovers, tube amps, preamps, hybrid amps and dacs so I think I have had good experience with them both. You must let them break in for at least 150 hours to know how they really sound. This is a must.
The CAST caps are a tad more tipped up in the upper mids. Some may like this as it sounds very resolving and open. For me this slightly tipped up upper mids caused my tinnitus to flare up. It was a tad too aggressive for me. I found this tendency when used in electronics, not in passive speaker crossovers. In crossovers they are magic. The Juputer caps have more top end air, improved Micro details, and an obvious improvement in bass impact. The Jupiter caps are far less expensive to boot. They seem to work better for coupling and output in tube amps and dacs.
I have had less experience with Vcaps, but one the one occasion I tried them they did not offer the "meat in the bones" weight and tone of the CAST or Jupiter caps. Crazy resolving however.
