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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
thecarpathian's avatar
thecarpathian
5,142 posts
 
Line emi meter.
oldhvymec
5,101 posts
 
Do you have a DMM Digital Multi Meter? Most valve amps like a certain voltage. Normally if it's LOW the transformer can be noisy. What will fix a low voltage issue is a Variac. I keep one here just for troubleshooting things like this. I also use it to bring up the old valve gear. 

It will supply 0 - 140 vac. 

See what the wall current is and swap to the other rail and see if that helps too. BUT I got a feeling you have low voltage and a BAD location for echoing the noise right into YOUR ears.. LOL

I use Triplites 2400s. BUT heck they have a transformer buzz. It maintains 120VAC on the button. I fixed 95% of THAT noise with silicone and dampening on the top and bottom of the conditioner along with about 15 lbs on top of the unit..

Regards..
arcticdeth's avatar
arcticdeth
1,572 posts
 
Iisten after 12:00am
vinylzone
288 posts
 
If it is a transformer hum, you might have a dc offset problem.  This is usually caused by some other device or appliance on the same circuit.  You either need to figure out what it is, or get a dc blocker.
dletch2
455 posts
 
The old point the finger at the other guy problem eh!


Carry the amp down to wherever your breaker box is. They usually have an outlet close by. Plug the amp in. Turn off all the other breakers. If the problem does not go away, odds are the unit has an issue. It could be a design issue of a MFG issue.
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