Musical Fidelity X10-D tube buffer

I've been in this hobby for around 60 years and, until about 2 months ago, never tried using a buffer.  That's when a friend gave me this tube buffer along with the DAC made by the same company. I'm writing this because I see that quite a few members as well as others randomly found on the internet have questions about this thing and thought I'd put in my 2 cents worth. I probably wouldn't even have tried it except that I've been trying to improve sound from the Echo Dot that I occasionally use as a source in my little all tube near field garage setup.   

Because the Dot has no digital output and I don't know how to access digital part of its circuitry I thought the buffer might make some corrections with results similar to a decent DAC. The hookup went as follows: Dot;  Nirvana electronics work P3 5W preamp;  Russian 30W no name tube power amp; B&W CDM1 speakers. With setup alone the sound is ok and I'm pretty happy with it but, of course, we all keep looking. 

I won't comment on sound quality; it's too personal a thing to presume but I can state without reservation that the change in sound is dramatic at least in this setup. Bass frequencies decame more dominant seemingly without noticeable loss in upper frequency detail. The surprising thing to me was that it seems also to have increased the overall signal strength for increased loudness. So, it's addition changed the sound in a major way but I can't say that I prefer it over what I already have without. Maybe it depends on what I'm listening to at any given time. 

Not very technical or audiophilish explanation but take it FWIW.