AC filtering/tweaks:
1. Install a dedicated line for your stereo....best to have several dedicated lines....like one for the amps, one for low level analog and one for digital....maybe more (especially if you have a home theater).  I had a friend who installed 4 double sockets in the wall and each individual socket had its own feed/circuit breaker right from the main input panel.  Much cleaner sound.

2.  Never stack a component with a big transformer with any other component.  The field from the transformer will effect the other component.

3.  Use split bobbin isolation transformers on your low level equipment.  150 watters will do.  Do not put them on the floor.  Hardwire them up in the air.

4.  Get some Hammond chokes and wire them across the line in front of your components.  See Audiocircle review threads and Audioasylum tweak posts.

 

6.  Bybee conditioners.....after tons of burn in, according to my crazed tweek bud, these things are the real deal.

7.  Treat you fuses with silver contact enhancers and replace fuses (if manufacturer allows) with audiophile grade fuses.

Other Electronic Tweeks:
1. Get rid of all magnetic material around a toroidal transformer and diode bridges.  You can substitute several large tie wraps for the steel cover and bolt in a toroidal transformer and you can use brass or bronze hardware to hold down any diode bridges...much cleaner sound.

2.  Get rid of all LEDs.  They add noise to the power supplies and mess with imaging and purity.  Use neon lamps or such for indicators., if needed.  Power indicators do what?  How do you know when something is on....it plays....don't need no stinkin LEDs.

3.  Damp your heatsinks for better sound.  If you rub your finger nail on your heatsinks and it goes "zing"  then that very sound is being added to the amp.....(CAUTION) Use damping material that can stand the heat...some heatsinks never get more than warm....some are super hot....use common sense....but this tweak works.