If you stream music from the internet, I can't recommend this more highly


I had been using a Roon Nucleus to stream Qobuz, with my Chord Qutest directly connected to the Nucleus. I thought I was getting pretty decent sound quality. And then I got a marketing email from Small Green Computer touting some of their optical gear. The basic idea is that normal cables and connections used to stream from the internet pick up noise of one kind or another (radio frequencies and electromagnetic something or other). But fiber optic cables and their connections/interfaces do not. I don’t know anything about anything, but it made theoretical sense to me, it wasn’t a huge amount of money ($1,400), and with a 30 day return policy I figured I could always return it if I didn’t hear any improvement. Well, I didn’t just hear a slight improvement; it was like turning on the lights in a dark room. Much greater clarity and detail, much better micro and macro dynamics, better timbre to acoustic instruments -- overall just more lifelike. Two quick examples: I’ve listened to some of Steely Dan’s top songs 100s of times over the course of my life, and this is the first time I’d ever noticed a particular and very subtle sound characteristic of Fagen’s keyboard in Babylon Sister. It’s hard to describe, but it’s like there’s a slight sound of air being exhaled by it. The other example: the specific timbre of whatever percussive instrument is used at the beginning of Copeland’s "Fanfare for the Common Man" (a recording by the Minnesota Orchestra). There’s more of a metallic sound than a drum skin sound to it that I didn’t know was there before. The metallic sound starts in the center and then projects out and to the sides, like a wave washing over you. Anyway, I’m just thrilled about having stumbled upon the whole "optical" thing and felt obligated to let others know about it. If you stream music over the internet, I highly recommend giving it a try. (The product I got was the opticalRendu, with the linear power supply option, and the Fiber Ethernet Converter Bundle option.)
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I'm not saying that any of these devices don't work, but what I don't understand is, don't streamers cache a certain amount of the data internally? If you are listening to music and you pull the ethernet cable out of your streamer, it will continue to play for a brief period of time. 

So I'm just not sure how "cleaner" ethernet packets going into a devices memory chips (cache) would improve the sound. 

Could anyone elaborate on this?
What matters is the analog signal coming out the DAC. These products have been measured and, yes, I'll say it again modern competent designed DACs have no problem dealing with the noise unless it's absolutely ridiculous. The devices do work the thing is it doesn't matter unless your DAC is junk. 
Been trying to figure out....  I am not clear what streaming services work natively with SGC devices.  I have my eye on Amazon Music HD due to its VAST collection.  I don't think Amazon and ROON works together  at all ?  Can someone shed some light ?  Thanks.

If you want to understand a TON of information about digital streaming that few people understand, check out The Hans Beekhuyzen channel on YouTube.
Here's a link to the MicroRendu review.  https://www.youtube.com/watch?v=2XRi9utNBl4

Hans is extremely objective and explains in plain English why you may or may not get any improvement from a new piece of digital gear.
Whether you'll benefit from optical depends mainly on how well your other components - server, streamer, dac - clean up the incoming signal.  The best ones do it for you.