Is an isolation transformer better than a power conditioner?

I took Charles advice a while back and now run Equitech on 4 systems. Best audio advice I ever got. Huge improvement IMO. (I had tried Shunyata and PS regenerators), There is a reason so many of the big boys use Equitech.

I have used isolation transformers and preferred the sound without. The sound was less alive. I use a PS regenerator and prefer that to without. Have fairly typical power usually reading about 2.7% THD.   

You may no need either. You equipments power supply can generally clean up AC, so if you have no line noise that is often in frequency ranges power supplies are not designed to filter, special power conditioning and cables may not do much for you. Isolation transformers are less expensive and often do the trick, it depends upon the noise and the transformer. Good luck sorting it out, no one who doesn't know the power in your area can give you a perfect answer though, IME.

Would clarify that Equitech is "balanced" power transformer. Not conventional transformer. Noise gets canceled by balancing power to +60/-60 instead of +120/0 (not a completely accurate way to describe it). Most of the noise affecting your system is produced by the reactive power generated by your own gear (depending how terrible your wall current may be). The  regenerators do nothing to mitigate that problem. Plus they limit current so you can't use it for your amps. You can (and should) plug your amps into the Equitech. Dynamic range is not limited (assuming you have the right size unit) and the noise floor is lowered dramatically.

I like to 'try new things' as much as the other audiophile, but I think when it comes to power it's best to ask oneself "what am I trying to fix". Let's start with the basic premise of power supply to our systems. It needs to be a stable sinewave. For us in North America, that means a 60Hz sinewave with as little distortion as possible, and no DC offset. For most people, this is indeed was is coming into your house, and it gets a bit muddled up from there, but maybe? So....I could write pages about this, but if you want to 'try and listen' please do - but it is so much better to start with a good power analysis (put a power analyzer on your mains and on the outlet(s) feeding your stereo. Start with that! I do have a power analyzer at my disposal and discovered the cause of much hum (mechanical, in transformers) was DC offset from my incoming power. Also, my voltage does drift (as most does) dpendant on time of day, and I would see moments of current distortion (iTHD) about 4%; my vTHD was typically <2% - all good, but could be improved. Start with something like that. I opted for a whole house surge supression system, a 20A dedicated line in MC (not Romex) and a large (3000VA) dedicated isolation tranformer with some EMI filtering included mounted near my breaker box. They HUM. If they are torroids, the might not, but standard laminated transformers will hum, and that's ok given my power issues. Result? remarkably quiet system in my music room. No hum (mechanical, audible, or otherwise) whatsoever. Dead quiet. Lots of transient ability in amps (the transformer is rated at 550A for 1/2cycle, 110A for 1sec, continuous at 25A, though my breaker/circuit is 20A). I'm very pleased with the result. THD is now <1%.   If you want a similar analysis, I would contact any electrical/power consulting company in your area; the engineer might be a bit perplexed at first, but I would guess he'd embrace a homeowner/hobbyist taking his power system seriously. If they don't, move on to the next one.