"Who would buy this?"
Back in the late 90's, Musical Fidelity launched a cheeky cylindrical range of goodies using valve and/or solid state - the original 'X' series. There was a soft toned valve preamp, similar phono stage, a dac which 'used to' sound/perform quite well and what I wanted to mention, a valve line buffer, the X-10D, which was marketed as an impedance matching box between inexpensive CD players and amplifier inputs. I can't argue about the impedance matching, as it offered highish input impedance which I thought at the time suited cheap CD player line outs better (I don't feel this way these days - read on). Stereophile tested it -
Sidebar 3: Measurements Although it could be conjectured that the presence of tubes in the X-10D might add a certain thermionic something to its sound, there was nothing in the measurements that would confirm that hypothesis. In fact, the Musical Fidelity appears to use a well-engineered...
www.stereophile.com
But the box as supplied really did alter the perceived sound repeatedly, adding a certain weight or 'thickening' to the sound and seemingly cleaning up subjectively, the 'hashy highs' of the then popular Maranta 63 KI Signature CD player which 'everyone' bought back then.
I got one for little money a good few years back and did a 'Rock Grotto' update on it with fresh Russian mil=spec valves. There was an improvement sonically with the update to the point I couldn't any longer 'hear it' in the system, so it was abandoned and now lives in storage along with the other stuff I accumulated. The transistors act as voltage doublers in the power supply I believe.
Sorry to drift, but here's the X-10D as supplied - would be interesting to see how the review box looks inside...