Preamp Output Capacitor: Mundorf Supreme vs. Supreme Silver Oil

You sure they're the correct values?

@imhififan If you read a lot of capacitor discussions, you can see some other people finding that the bass response of the s/g/o decreases over the first 300 hours (e.g. https://forum.audiogon.com/discussions/mundorf-silver-gold-in-oil-supreme-caps-any-good).

@noromance Yes, actually the original reason I started modifying the capacitors was because the miflexs were right on the edge of being too small for my amplifier's input impedance.

@alexberger Although the miflexs' had nice tonality, they presented a very flat image in my system. Adding in the Mundorfs put a lot more layering into the soundstage. It very much went from 2d to 3d.

Also, I just discovered the thread I cited above did have some s/g/o to silver in oil comparisons. It was hard to explicitly search for differences because the only difference in terms is gold (and people write out the cap names variably).

Looks like maybe supreme silver oils do have better bass.

@alexberger and I'll probably also try some Duelund tinned copper. Thinking about putting those on one output and one of the Mundorfs on the other.

Those Duelund tinned copper caps are so special. If you can afford those, they will easily surpass the Mundorf caps in every sonic area. I think you suspect that is true.  They are pricy! 

Yes, actually the original reason I started modifying the capacitors was because the miflexs were right on the edge of being too small for my amplifier's input impedance.

Be careful- just increasing capacitor values can get you into trouble. The output section probably the least, but in many cases, the designer is juggling the inductance that a larger capacitor has against the capacitance- and has arrived at a value that has the best compromise between bass bandwidth and coloration. Bass bandwidth good, coloration bad :)

(This is why we have direct coupled outputs on our preamps- this problem is avoided.)
There is a timing constant involved (which sounds like you might already know) the formula is F = 1/R x C x 2Pi
Its a bit inconvenient as stated, but if you replace 1,000,000 for the 1, then R will be in ohms, C will be in microfarads and F will be in Hz. Ideally you want the -3dB point (which is what this formula gives you) to be no more than 2Hz- allowing the preamp to then have no phase shift at 20Hz which will give you neutral bass. R in this case is the input impedance of the amplifier.