Good small/single outlet power conditioner for preamp.

I would continue to troubleshoot until you are certain of the problem, then solve that. It will be very interesting to see if the problem goes away when using a power strip only.

Update: The Furutech tp-609 passive power distribution unit AND the Equi=Core 1800 balanced power conditioner are BOTH hum free!!

This confirms some sort of mismatch in power or grounding between the Puritan PSM156 and the Backert Labs Rhythm 1.4 preamp. 
 

So if I elect to keep the preamp, I will need to invest in another power conditioner for the main system here… maybe a new thread for that… Unless anyone has a good recommendation for something at least relatively close to the $2300 price of the Puritan, but some more $$ is fine to consider. The Puritan is so good at its price, I’m worried what it’ll take to match its performance. 

There are many excellent power conditioners on the market.  Furman is only one of many and Erik_Squires recommends this brand mostly because he owns one and likes what it does.  I use Shunyata and many others use other brands.  There is an Audioquest Niagara 1200 available used here for around $700-800.00 which is an excellent value as well. 

+1 for the Audience AR2 P.  If you can swing the bucks go for the AR2 T for better SQ. I have one cleaning the power to my streamer only so I do not shut it off.  All other components are connected to a Shunyata 6000T V1.  

@jriggy I am a Synergistic Research dealer, so take it for what you will, but they make a PowerCell One for plugging one single component direct into the wall. I’ve personally been a big fan of the PowerCell series long before I became an SR dealer, moving from higher end PS Audio conditioners. The PowerCell One retails for $1,095 and may be worth looking into if you are just looking to separate your preamp from the rest of your system’s conditioning.