My DS Sr runs balanced direct into a fully balanced 500wpc solid state power amp. The sensitivity of the system is such that I can hear the DAC’s noise floor when nothing is playing and the room is quiet. (It’s not the amp’s noise floor – the white noise vanishes completely when I engage the DAC’s 20dB output attenuator or switch the DAC off.) And my goodness can it play loud if I want it to. Most modern recordings with little or no headroom are house-fillingly loud with the DAC volume set to 50.
So no: I do not need a “gain stage” between the DS and my amp.
My amp’s input impedance is 50k-ohms, which is not far shy of the BHK Pre’s 66k for balanced. The DS DAC output impedance is almost as low as the BHK Pre’s. So no: I do not need a “buffer” to better match my source and amp electrically.
Interestingly, I find that engaging the DS output attenuator distinctly degrades the audio quality in my very highly resolving system, despite the reduction in background noise. It could be as simple as a slight roll off at the top end but something becomes lost in terms of fine detail, the decay, the imaging and soundstage etc.
Given that I’m at the point where something as trivial as a resistor shunt to ground causes audible degradation in a minimalist system that’s producing some of the best audio quality I’ve ever heard (and I’ve heard a decent amount), it’s extremely hard to imagine that adding an entire pre-amplifier’s worth of additional circuitry and another set of interconnects would deliver a purer signal. Purity is what I’m after – tone, timbre, colour, ambience etc must come to me in the recording itself.
As with everything else, it comes down to what you like and what you want from your system. A pre-amp can solve problems with impedance and gain matching, it can offer flexibility with multiple analogue sources, or it can provide some kind of additional tone control or harmonic sweetening. If - as for me - none of those are relevant, you can happily live without a pre-amplifier between your DAC and your power amp.