Snipes, I have owned a Sonic Frontiers preamp before with the same problem but my hiss was in the left channel. Called SF and they told me that the Mosfet transistor that followed the tube had become noisy & if I could tolerate the hiss it was not necessary to replace. To cure this hiss of course is to replace the Mosfet follower.
Another thing to keep in mind as when you swap out tubes it is important to wait at least two minutes after turning the unit off before doing so otherwise damaged can occur to the Mosfet follower. I am assuming the SF Line 1 is a hybrid like the SFL-1 which I had owned. Hope this helps.
Another thing to keep in mind as when you swap out tubes it is important to wait at least two minutes after turning the unit off before doing so otherwise damaged can occur to the Mosfet follower. I am assuming the SF Line 1 is a hybrid like the SFL-1 which I had owned. Hope this helps.