Line conditioner...

plus one for 68pete. I've had great results with their products.

If you turn on your system, the source is a good CD/SACD, well made, with a good power supply. Turn the volume all the way up, with nothing playing.
My system you hear NOTHING, no noise anywhere, from the tweeters, the mids, the bass drivers, the subs, every source of noise is gone. pure silence!

There is a few thing powered up too, 7 power amps, Preamp, Active OXO, TT (sometimes), Sdac x 2 , Streem, TV, and MC

Some settle for a whole lot less and call it good. NO NOISE, ZERO.

BUT

There is a slight hum at the conditioner closer than 2 feet. It goes away, at 25% volume when under load, and stays gone until 85% volume, then returns from 85-100%. If I stay at 100% for 2 seconds, that goes away also. To me that is a NO NOISE system... I have one conditioner in another room, both plugged into the same 20 amp circuit and the same outlet.

I guess you would call that less noise, but not sound better.. Makes me think something is wrong if it sounds better. Why have filter caps on a power supply if it doesn't FILTER very well.. Kinda short in terms, but long in meaning, AY?

Regards

There is a slight hum at the conditioner closer than 2 feet

If that's from the conditioner itself it is likely to be mechanical, should just be a matter of finding the right screw to tighten.

Have you tried the same test without having the conditioners in the circuit? I'm genuinely interested in understanding what these things do that the manufacturers of our amps don't consider worth doing in their own power supplies.

@ mikeydee,
Absolutely! I have had great result from my Inakustik conditioner. Which one did you try yet?

I recently purchased a Panamax strip and it definitely helps the sound of my system.  I noticed it right away.  I don't spend a lot of money on this hobby, but I get reasonable sound with a minimal expenditure (Teac AI101-DA (DAC integrated amplifier) into Sony bookshelf speakers.  I am using Toslink from my TV with the YouTube Music app.  It's sounds good enough for me.