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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. 
oldschool1948

Showing 5 responses by oldschool1948

oldschool1948's avatar
oldschool1948 OP
507 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?


oldschool1948's avatar
oldschool1948 OP
507 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.
oldschool1948's avatar
oldschool1948 OP
507 posts
 
@gloriousunicorns  I'm using Silnote XLR cables from my BHK pre to the 250 and Transparent Super XLR cables from the BHK pre to my DirectStream Sr. DAC.  

I use Tungsram 7dj8 tubes in my pre amp and 250.  I've tried 3 different sets of Tungsram 7dj8 tubes and a new set of PS Audio 6922 tubes and got the same result.  I will try it at another house - great idea.  I just hate moving that monster around.

@dledletchThanks for the info.  I'm grasping at straws.  Luckily, I can send it back for a full refund. 

oldschool1948's avatar
oldschool1948 OP
507 posts
 
@lowrider57 There is no hum thru the speakers, and I can only hear it up close.  PS Audio tells me there’s nothing wrong with the amp, so I will believe them.  I ordered the Humdinger.  Can’t wait for it to get here 😀
oldschool1948's avatar
oldschool1948 OP
507 posts
 
I installed the HumDinger; it made no difference.  I replaced my VooDoo power cord with a new GR Research power cord.  Each day when I first turned on my system, I put my ear close to the tubes and could hear a faint hum.  After about 30 minutes, the hum was barely perceptible.  

The amp came back from PS Audio with new PsVane stock tubes.  Because they sound better to me, I put my used Tungsram 7dj8 tubes back in.  The slight hum came back.  I put in a new set of Tungsram 7dj8 tubes.  The amp was dead quiet.  Hopefully, it will stay that way for a while.

After 40+ years of SS gear, I'm beginning to understand even more how much I still don't know about tube stereo equipment.  I started buying tube gear about 3 years.  It's been an interesting journey.  
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