[Ericus Rex]

Big fish,

The lower gain settings are supposed to give you wider bandwidth.  But I haven't really noticed a big improvement with different settings.  I use the different gain settings to equalize the volume differences between my phono and linestage inputs.  Try the lowest gain setting and see if the noise level goes down another degree.  You'll of course have to crank the volume pot up a little higher to achieve the same volume.

[Bigfishhk]

Try some RCA 6sn7gtb's, 1963. RCA made some sweet tubes back in the 60's.

I have a pair of the RCA GTB, though not sure what year (60's I think). they are excellent.

[decal]

Not exactly.  The Tempest is the Stereo 90 with a simple preamp section added.  The 99 is an entirely different beast.  The 6SN7s in the Tempest are drivers for the power tubes and the 6SN7s in the 99 are voltage gain and mu-follower stages.

I stand corrected.Thank you.

[Ericus Rex]

I will correct myself; the original Tempest is based on the 88 amp.  The T II and T III are based on the Stereo 90.  Sorry for the confusion.