Hi Jon, I had that nasty flu a couple of weeks back. I'm STILL feeling the residual effects. Hope you're feeling better.
I'm confused. I looked up the Koetsu Onyx on the Elusive Disc website. It states that it has an output of 0.2mv. Is this cartridge offered with an "optional" ouput of 0.6mv also? Is the information I am being provided incorrect?
The difference between those two figures is somewhat significant. A 0.2mv output would require an optimum gain of 64db vs. 55db gain with an output of 0.6mv.
If your Melos is providing you with either 54 or 78 db of gain, you could now understand why you are using the lower output setting. A 0.6mv cartridge output would work almost perfectly with your 54db phono gain stage setting as (by the numbers) it would actually require 55db. You are really not going to get any closer than that. BUT, if it is in fact a 0.2mv output, it would also explain why you are experiencing the sound characteristics you described in your original post.
I think now you can see why I use my little calculations/formulae. THEY WORK! It helps to take all of the guess work out of these equations. They allow you to make a more accurate selection of cartridge/phono pre right from the very start or, in the very least, give you a closer approximation of where you need to be. (Measure twice, Cut once)
If you could, recheck your cartridge output. After that has been firmly established, we can then address the capacitance/operation issues.