Buffering and caching are two entirely different concepts.
Every device that intakes a data stream from network or ISP will buffer that data stream. It is done to create a stable consistent flow of data irrespective of the incoming speed. If it’s too fast, the buffering regulates it down to the data flow that meets the requirements of the downstream processing. Same with slower speeds…it will buffer the data up until the requirements are met. Buffer size us typically not that large and is dictated by the design and the needs of the downstream components/processors.The data is not maintained in the buffer for too long.
Caching is typically a much larger data store (could be in memory or SSD) that caches the result set and stores it. Depending on the design, most of the critical processing may actually happen from the cache and that could result in cleaner downstream processing because some of the impacting entities like noise, etc had already been taking care of. Reading and processing data from cache in this case is similar to reading a CD. You can perform the remaining processing and further purify the data when it is converted to either the USB or SPDIF outbound signal that the DAC will understand.
If you pull the Ethernet cable out of your streamer that utilizes buffering only, you will probably get about 30s to a minute of play.
In the case of caching, depending on the defined size of the cache and what’s been cached, you might be able to listen to the entire album or the entire playlist.
In my experience, the impact of Ethernet tweaks is less evident with streamers that use caching. For example, with the Aurender you can A/B two different Ethernet cables by caching the same song twice, version A with cable A and version B with your second cable. It would be impossible to do with the buffering only streamers. Data in the cache will remain until it rolls of due to capacity or you clear the cache manually.
Comparing a ripped file to Qobuz or Tidal might also be a fool’s errand. You can never possibly know and ensure that the two versions are the exact same master. So the difference in sound may be attributed not only to CD vs. Streaming but also to the version of the streamed album you’re comparing your cd or cd rip to. The most critical link in the chain is immediately before the DAC. If you’re using a server, what happens on that server as long as it’s properly sized, is far less critical.
Quality of the streamer is extremely important. You can never make a mediocre streamer sound like a great one by adding gadgets, no matter how expensive they are. Just like you can never soup up a Civic to perform like a proper sports car, no matter what you change or add to it (not knocking on Civics…great cars).
Just adding my $0.05 here…
