Buffer amp no gain

@erik_squires You literally just described the reason preamps exist.

Yes, Erik has it right, the pre-amp can amplify the signal, it also attenuates the signal and sends a signal to the amp at the right impedance. I've never seen a top audio system without a preamp (some pretty good ones without but not state of the art systems).

The unity gain "buffer" that I like involves the use of transformers.  I've heard a few and liked how they remove hard and artificial sounding "edginess"  without sounding murky or dynamically dull.  The attached is a discussion of the subject:

I think Luxman, maybe among others, experimented with transformer based volume controls.   I have to say I've always been intrigued by using transformers either as volume controls or output buffers offering galvanic isolation and balanced outputs.

Erik,

The problem with most transformer volume controls was the limited number of volume steps—the right volume seemed to always be between adjacent steps.  The are some nice ones offered my MyEmia (autoformer) that has many steps and remotely controlled volume and balance.  They used to offer the autoformer and relay switching as a kit, so one could build the control into one’s own gear, but I think the kit days are long past.  

noromance

micro iTube2 by iFi audio - Vacuum Tube Buffer and Line Stage Preamplifier (ifi-audio.com)

Unless I'm sadly mistaken, they don't seem to be available.