Silver cables added resolution

If the hiss is independent of the music playing or not, it's bad shielding.

WW does not shield their cables AFAIK, and it does matter, even with XLR.

Quote, from an Engineering Textbook:

"Silver and copper are the two most conductive metals known to mankind, with gold following behind in third place.
The conductivity of silver is 63 x 10^6 siemens/meter.
The conductivity of annealed copper is 59 x 10^6  siemens/meter."

So roughly 7% higher for silver vs. copper.  It's a measurable difference, but a clear and direct audio difference?--doubtful.

IMO there are clear and essential audio differences between different cables, but if all other things are equal for silver vs. copper (which is not actually possible or desirable), they are essentially the same for audio applications. So then, it's probably design, purity, quality control, metal treatments, manufacturing and terminations that matter more than one metal vs. the other. 

Diagnosis: Don't change your electronics to match your cables. Buy what sounds best to you with your equipment, knowing that a lot of work has been put into finding and offering the best.

Your experience is common. Know that proper assessment of cables demands they be compared in sets, at least initially, according to manufacturer recommendations. So, all the comments about assessment of particular cables' attributes  when used in mixed sets are pretty much worthless. 

It is common for silver OFC and silver conductors to show more brilliance and noise, as you hear. There are many variables involved, but silver does not always mean brighter. Case in point, the Iconoclast cables I just reviewed for Dagogo.com are better balanced in terms of frequency spectrum than most copper cables I have used. So, simple selection of conductor material alone is not a definitive answer. Imo, AWG is as important to obtaining a less strident sound as is conductor material. 

If you hear more hiss, then you have an elevated/increased upper frequency range with that particular combo of cables. It typically is perceived as adding more information. You can hear this easily when you listen to music. Put the older cables in, and the hiss diminishes, and the brightness is not there. 

I can tell how bright a cable will be to some degree based on such hiss; I know the cable has brought more upper end energy/emphasis before even hearing the first note. When a cable is less "hissy", then you will have more balance toward the bottom end of the frequency spectrum. I regularly tune systems with selection of the appropriate cable that confers the proper qualities, such as the degree of emphasis (or not) of the upper end of frequency spectrum. 

Most audiophiles do not have a thorough understanding of these things, because they have never used and compared complete sets of cables. It is simply too challenging in terms of cost/time/effort for most. They mix them and have no baseline to gain more developed understanding of these things. The worst are those who think the conductor material does not matter. They spread misinformation, wretched system building advice, when it comes to using cables to elevate system performance.  

I am not interested in arguing my observations and recommendations. 

For what this is worth....
I was discussing the impact of all silver versus hybrid silver and copper with a rep from Kimber Kable.  I was able to get 2 sets used from a friend and was trying understand what was the difference between the cables.

"They're explanation of the intended difference was all 'silver' would transmit the information better and the result would be excellent high frequency performance and clarity in details.  The hybrid was intended to enable dynamic impact especially on lower frequencies because 'copper' tended to provide better bass performance." 

They both were a noticeable upgrade from the Better Cables I was using and I couldn't differentiate between the all silver and hybrid silver copper (1 copper line used for the ground, 2 silver used for + and -).

Have you measured it? done any blind A B testing? Then it is all in your brain.