Who makes the best copper cables?

Top Cardas clear, Clear beyond are very good I have clear beyond for interconnects ,and Clear for Loudspeaker cables , excellent results !!

Beware, model-level performance varies within each brand.  For example, Cardas offers many different cable lines and different price-points.  If someone recommends "Cardas", ask them WHICH Cardas?

One minor point, I had Audio Envy many years ago, and they were dogs and I tried to give them away, but no takers... 

I like my current Audience FrontRow speaker cables.

@bthrb4u

I'm confused. 

You have Furutech Project-V1, but find them too uncolored?

I'm not so lucky. But I do have Furutech throughout my system. I started with the DPS-4.1 power cord with FI-50 NCF terminations. I loved it, so I bought more. They took ages to break in, but still retain a warm, rich, house sound. 

I found a used Furutech Nanoflux NCF power cord and snapped it up. This was their top of the line prior to V1. It’s great, and objectively better, but more transparent than the DPS-4.1 with FI-50 NCF terminations. 

My advice, which may seem counterintuitive: Have someone make you a DPS-4.1 power cord. Place it strategically in your system. You may find it adds the character that you're looking for.

Good luck!

Who makes the best copper cables?

A very small company in Mordor.   They forge the copper cables in the fires of Mount Doom. 

There really are only consumer grade and data center grade cables. Consumer-grade Ethernet cables are typically designed for home use, offering basic performance and durability, while data center quality cables are built for high performance, reliability, and often include advanced shielding and materials to handle demanding environments. Data center cables are generally more robust, supporting higher data rates and longer distances without signal degradation.

If you believe it will make a difference, I would recommend Companies like GEARit and Amphenol TPC Wire & Cable offer a range of data center-grade Ethernet interconnects designed for high performance and durability. 

Some people believe consumer electronic companies have some magical formula when it comes to ethernet interconnects, but it's likely they're using data center grade from one of the companies named (or a few will use consumer grad)  and then make it look fancy.