Background noise

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.

yes...i'll look into the tubes. Actually, i just opened it, and noticed that the housing of one of the tubes is a bit loose. so, that might be the culprit...or one of the tubes. i'll keep you posted. thanks.