2. amps-preamps
  3. 166258-110858

Detecting “Dirty” Power

I bought a used BHK 250 still under warranty. It is plugged into a Denali S power conditioner.  I heard a hum coming from the area around the tubes.  I cannot hear it from my sitting position and it doesn’t effect SQ, but I want it gone.  

I sent it to PS Audio; they tell me there is no hum and sent it back. They implied I mostly likely have a power problem and recommended some troubleshooting steps.  I unplugged everything from the 250 and plugged it straight into the PS Audio receptacle.  The hum is still there, but it is not as pronounced.  A P15 power regenerator might fix the problem, but I want to know if I have a power problem before I do anything.

How can I determine the quality of the power coming into my house and out of the receptacle? FYI, the Denali is plugged into a PS Audio receptacle/dedicated 20 amp line.  I have a whole house generator w/ transfer switch and whole house surge protector. 
128x128oldschool1948
oldschool1948's avatar
oldschool1948 OP
503 posts
 
Thanks everyone for the suggestions.  

My breaker box is in my basement listening room.  I have a dedicated 20 amp line connected to the box.  Connected to the PS Audio receptacle's top plug is my Denali power conditioner.  Everything but my 250 is plugged into the Denali.  The 250 is plugged into the bottom plug. 

I will unplug the Denali leaving just the 250 pugged in to see what happens, and I will try different power cords. 

While researching, I came across the Audio Magic Signal Purifier for Power Cords https://highend-electronics.com/products/audio-magic-signal-purifier-for-power-cords.  Does anyone know how it may compare to or differ from the https://avahifi.com/products/humdinger-dc-line-blocker?


vinylzone
288 posts
 
I don't know about the first link.  It won't block dc offset, and makes some "interesting" claims.  The AVA is what you should try.  Alternatively, Emotiva makes one too:  

https://emotiva.com/collections/accessories/products/cmx-2

I haven't tried it yet, but was going to order one shortly.  Both that and the AVA should work if the problem is indeed dc offset.
gs5556
1,236 posts
 
Start at step one: lift the ground of the amp by using a two prong cheater plug. If the hum goes away then it’s a ground loop.
oldschool1948's avatar
oldschool1948 OP
503 posts
 
I unplugged everything but the 250 and changed power cords.  Slight hum is still there.  I ordered the HumDinger.  I'll follow-up after I try it.
dletch2
455 posts
 
The Humdinger fixes transformer hum. You said the hum was near the tubes. If that is the case, it will not fix it.
More to discover