AudioQuest RF Stoppers

For me, they are super effective on my phono cables, between the turntable and the phono preamp. I used to hear radio stations faintly when listening to records. The AQ RF Stoppers cleaned up this noise very well.

Notably, the phono signal is often the lowest voltage in a system, requiring the most amplification boost, and a little bit of RF noise that the cable picks up gets boosted along with the signal. However, by the time you get to speaker cables, RF noise really shouldn't be a factor.

I don't know what's causing your hiss. Sure, go ahead and try the RF Stoppers -- they aren't that expensive, but my guess is you may be hearing something else.

Hi Mark if you think the AI L1 is causing high idle noise (which it probably is, being tubed) then simply turn it off. Does the noise diminish? Next, disconnect your interconnects from the power amp & see what changes; my guess is, that won't change the idle noise. If it doesn't then RF stoppers are probably not what you need. If your power amp is also tubed, then any noisy or gassy tubes therein also contribute to high idle noise. Even solid state equipment produces some thermal noise, although full-balanced topologies tend to run significantly quieter.
I will say that RF stoppers that I once placed around signal interconnects acted as filters well down into the audio band, which significantly degraded HF performance. This phenomenon will of course vary according to cable design, but just be aware of it.

Buy TDK ferrite cores, 99 cents each. No need to pay Voodoo pricing...