4 (2 in 2 out) HFC RCA Magnetic Adapters.

Further Information: 

Up for sale, a set of 4 (2X output, 2X input) High Fidelity Cables Magnetic RCA Adaptors. You place the "outgoing" set on the outputs of a device (DAC, Preamp etc) and then the "input" side of the receiving device. 

The Magnetic Adaptors were designed as a lower cost point of entry into High End Cable's magnetic conduction technology. Their cables started at about $1300 so these offer a lower price taste of what they can do. 
They add an amazing timbral quality and really accentuate the presence region in a nice way. They also add a lovely dynamic quality and add intelligibility. Very addictive. Ideal if you have a dark or a neutral setup that needs some extra life.

I experimented with placement and found that there is some flexibility with which cables you use them on if you are running a source, a preamp and a power amp. They have a very strong effect and 2 sets will more than enough for most systems.

Audiobacon review:

"This experiment had some unexpected results for me. I did expect some kind of improvement but not at this magnitude. These innocent-looking little magnets were not only able to improve all sonic elements of this system, but brought it to heights I believe only achievable with at least five times more money. However, given that the magnetic conduction technology is patented, you might not even get this “magnetic signature” without Rick’s products. If you’re stuck finding an inexpensive way to upgrade your current 2-channel system, I cannot recommend the High Fidelity Cables Magnetic RCA Adapters highly enough. It’s a no-brainer. So much so, I spoke with my wallet and placed an order for a pair. "

I tried one of these on a really good quality SPDIF cable and it subjectively brought a really nice uptick in dynamics and clarity. So even though they aren't specified as being useful in that scenario, they made a real improvement for me.

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