Preamp Output Capacitor: Mundorf Supreme vs. Supreme Silver Oil

My experience matches that of  @salectric 

With tube gear where the input impedance is typically 100K or more, a 0.68uf coupling cap is fine.

The smaller value you can get away with, the better the cap itself will sound (and no need for a bypass). That is why we have a direct-coupled output in our preamps, so that the significant cap in the circuit is only 0.1uf.

Could someone explain why adding a 0.01uF capacitor in parallel/bypass with a 2.2uF capacitor improves sound quality? 
If this is way off topic and I’ll delete the post and ask elsewhere.
Thanks.

Not everyone agrees that a small bypass cap improves sound quality.  I have tried bypass caps in all sorts of applications going back literally 40 years and I haven’t found a single instance where the bypass improved sound quality.  The bypass certainly changes the sound; usually the bypass makes the sound brighter, leaner and less coherent.  I much prefer the sound of a single quality cap like a Copper V-Cap over any combination of caps with a bypass.

You may reach a different conclusion so by all means try it yourself, but don’t be surprised if you tire of the sound with bypass caps.

It depends on the combo and position. The Vcap Odam & Cuft bypass are a match in heaven. Chris from Vcap turned me onto it. I will say it is magic on the output of a dac which is where I have used them on 5 occasions now. I am sure they would sound as wonderful together on the output of a preamp.  I am using them on a tweeter next and will report back. 

Some combos just work and some just dont.  Learn from experience.  The Jupiter copper foils bypassed with the Duelund silver foil bypass cap also works wonderfully.  In my experience the two examples work and I have used them extensively.