Background noise

"I still believe a gain mismatch is contributing to the OP)'s noise issue"

As you should, you are correct! In fact it is central to the issue. IMHO of course.

Well, in terms of load, I checked the specs of the Sumiko, and there is no problem. So, that is not an issue.

I agree that the load mismatch can exacerbate the problem, but I do not think it is the root cause or the central issue -- the problem is that no matter whether the turntable is connected or not to the preamplifiers, when I turn up the volume I hear a lot of background noise. The underlying problem must be somewhere else...at this point I am convinced it's a tube issue. Thanks.

Sorry, I didn't pay much attention to your original post........

If you are getting tube rush/hiss without a TT connected, then you have either a phono stage with a high(ish) noise floor, noisy tubes, or very efficient speakers which will reveal noise floors not readily apparent with less efficient speakers (like 102db v 86db speakers). Ask some owners of horn speakers. Some time ago I had 82db speakers and every thing was quiet. Then I got some 92db speakers and discovered all kinds of hums and buzzes. :-)

The only way to figure this out is get some phono stage quality tubes tested for low noise. If you still get the hiss you've just got a spare tube or two, or four, etc, and a different decision to make.

I'll add that the Shindo units I have heard are astonishingly quiet, so that would also make me lean towards a noisy tube as the culprit.