anyone upgrade their RCA connectors on Cardas RCA cables?

To @westcoastaudiophile the physical differences I’m aware of are more mechanical in nature, and less measurable, negligible, as I understand it. Even Cardas will state they have cables that measure the same and sound different. I’ve experienced this myself, two pairs of the same, side by side with different type connectors/connections. If you can’t hear a difference, it does not matter or makes no difference, to each his own.  

Clipped Notes:

• Contact Resistance: High-quality crimping, often referred to as a "cold weld," can achieve extremely low contact resistance—typically less than 10 mΩ—an airtight, metal-to-metal bond. .
• Impedance Consistency: In high-frequency or precision lab environments (e.g., >18 GHz), soldered connections can sometimes offer slightly better return loss or Voltage Standing Wave Ratio (VSWR) due to more predictable and consistent resistance levels.
• Mechanical Strength: Crimped connections generally offer superior vibration resistance and mechanical durability, as soldering can create a "brittle point" where the stranded wire meets the solid solder.
• Signal Loss: For most audio and commercial RF applications, the difference in insertion loss between a properly executed crimp and a professional solder joint is negligible, often measuring less than 0.1 dB.

I’ve experimented with the Cardas GRCM and GRMO RCAs from Cardas on that Mogami cable, as well as with ETI Kryos.

That Mogami cable is very good (and underestimated) when paired with any of the above connectors.  

My Headwaters interconnects are comprised of that Mogami with either Cardas RCAs or ETI Kryos.  Loosely speaking, I’d equate the Headwaters to the Cardas Clear Cygnus.

I suspect your Iridium cable uses one of the above RCAs.  It’s difficult to tell from looking at them.

I find the ETI’s to be a subtle improvement over the KLEs - not enough to change if you’ve already built a cable, but slightly more nuanced.

In general, I find the ETIs (and by inference, the KLEs) to have a slightly more extended top end than the above referenced Cardas plugs.

The above two Cardas connectors tend to focus your attention on the upper bass and lower midrange, and in many systems, folks will prefer the Cardas for their "warmer" sound.  

Note:  I have not tried Cardas’ top of the line SRCAs.

Given that the top end on their Clear Beyond cables is more extended, I suspect the SRCAs approach the ETIs in upper frequency extension.

Note 2: The relationship between ETI and KLE is a complicated one.  ETI used to publish their origin story before they rebuilt their website.  As I understand it, the current industrial designer at ETI designed the original Eichmann Bullet plugs.  At some point, Eichman became KLE, and ETI was formed at some point after that.  There's some sort of licensing agreement between ETI and KLE, although the product designs have diverged a bit while stil maintaining the low mass concept.

Thom @ Galibier

@thom_at_galibier_design, thank you.  This is the type of detailed answer I was looking for, and I will probably be keeping my Cardas Iridium cables in their factory config.  I wonder how the Furutech 126(g) RCA connectors compare to the original Cardas GRMO connectors?

I haven't played extensively with Furutechs.  Some of them are quite good and are very similar to Cardas - perhaps a bit more upper frequency content.  If you're changing from the KLEs, I wouldn't bother.

... Thom @ Galibier

Prior to Sept 2012, in 2005 or 2006, Robert Woodland who was ETI by name, sold his portion of the business to ETI. ETI went into voluntary administration in Sept 2012 and the existing directors of ETI re-purchased ETI in Oct/Nov 2012.

Up to Sept 2012 Keith Louis & Patricia Eichmann were earning royalties on their concepts and ideas (IP and Products) sold by and through ETI. From Oct/Nov 2012 onward, Keith Louis & Patricia Eichmann have received no further royalties from their IP and Products even though ETI has been and still uses and sells their IP and Products.

You should know that Keith Louis Eichmann invented many more products than just the Bullet plug for ETI, in fact, most of them.

Even though ETI were instructed to stop using and selling KLE's IP and products, by Keith Louis & Patricia Eichmann, ETI have continued to use and sell KLE's IP and products.

As a result Keith Louis & Patricia Eichmann decided to begin again and started up Keith Louis Eichmann Innovations (KLEI), in 2013/14, by releasing their next generation Eichmann Bullet plugs, the new and improved KLEI Harmony (Bullet) plugs."