[Alphonse]

Need help diagnosing and/or resolving a mechanical hum (not thru speakers) issue I recently noticed. I have the following gear; Bryston BP-6, 2 Bryston PP300SST monoblocks, Arcam CD37 SACD/CD player, Pioneer BDP-51 Blu-ray player, Samsung LCD HDTV, Dynaudio speakers, DH Labs interconnects and speaker wires and one pair of Bryston interconnects.

Recently while listening to music I went over to change CDs and I noticed hum coming from the Arcam CD player. Upon further investigation I noticed both PP300s also had hum.  No noise from the pre-amp or thru the speakers, TV and Blu-ray player off.

I also noticed that it is an intermittent issue, i.e., after further listening that session the hum went away in both amps and the Arcam. The next day when I powered everything up again there was no noise but a couple hours later the hum reappeared. The next day when I powered everything up the amps and Arcam had the hum to start.  What seems to be consistent is the amps and the Arcam are either all quiet or all making the noise at the same time, just no predicting when.

Also this is noise that is audible from about 1-2 feet away, but not from the listening position (11 feet away.)

Anyone have ideas why this happens just to the amps and Arcam but not the BP-6 or Pioneer or Samsung.

I did do some searches on mechanical hum and found that one explanation can be power supply saturation from DC in the AC line.  And although it may not affect quality of sound it may not be great for the power supplies.

What else may explain this? Anyone else experience this?  If so how did you isolate the problem and resolve?

Or as my subject line states, is it not a significant issue.

Thanks,

Al

 

[brucek]

Anyone have ideas why this happens just to the amps and Arcam but not the BP-6 or Pioneer or Samsung.

Whether a transformer is suceptible to hum with asymmetrical line conditions depends on its type and construction. Small DC bias in the neutral to hot generally will cause more mechanical noise in toroidal transformers than the standard EI type, but EI transformers are certainly not immune.

A power amplifier I use to own with a toroidal transformer had quite a nasty hum whenever DC was on the line. I presently use an Arcam Alpha 9 CD player that will hum from DC bias when it's turned off (since the power switch merely unloads the transformers secondary and doesn't shut off the primary circuit). My solution for that is to leave it on all the time......

Producers of transformers do strive to reduce this problem by engineering the windings and core so that magnetic flux densities remain well below the saturation levels, and will often specify the DC-voltage which the transformer can handle without getting noisy.

There's not a lot you can do about the problem. In worse cases people will construct a DC blocker circuit, but they're a bit nasty, since they are in the primary circuit and might be considered a safety issue. Certainly any line conditioner that uses an isolation transformer will strip all the DC component from the line.

In mild cases where the problem comes and goes from a small amount of DC intermittently on the line, I never felt it was too serious. Any harmonics from slight saturation would be removed by the power supply. Overheating should only become an issue in the worst of cases.

brucek

[jethro]

Al,

In the past, I had a problem with halogen torchiere-type lights causing mechanical hum in my 4B-St. The lamps didn't even have to be on the same circuit to cause the hum. I have no idea why they caused the hum but the lamps went in the garbage. Perhaps you have a similar problem ?

--Steve

[NewBuyer]

Need help diagnosing and/or resolving a mechanical hum (not thru speakers) issue I recently noticed. I have the following gear; Bryston BP-6, 2 Bryston PP300SST monoblocks, Arcam CD37 SACD/CD player, Pioneer BDP-51 Blu-ray player, Samsung LCD HDTV, Dynaudio speakers, DH Labs interconnects and speaker wires and one pair of Bryston interconnects.

Recently while listening to music I went over to change CDs and I noticed hum coming from the Arcam CD player. Upon further investigation I noticed both PP300s also had hum.  No noise from the pre-amp or thru the speakers, TV and Blu-ray player off.

I also noticed that it is an intermittent issue, i.e., after further listening that session the hum went away in both amps and the Arcam. The next day when I powered everything up again there was no noise but a couple hours later the hum reappeared. The next day when I powered everything up the amps and Arcam had the hum to start.  What seems to be consistent is the amps and the Arcam are either all quiet or all making the noise at the same time, just no predicting when.

Also this is noise that is audible from about 1-2 feet away, but not from the listening position (11 feet away.)

Anyone have ideas why this happens just to the amps and Arcam but not the BP-6 or Pioneer or Samsung.

I did do some searches on mechanical hum and found that one explanation can be power supply saturation from DC in the AC line.  And although it may not affect quality of sound it may not be great for the power supplies.

What else may explain this? Anyone else experience this?  If so how did you isolate the problem and resolve?

Or as my subject line states, is it not a significant issue.

Thanks,

Al

I know how you feel, and then some - I absolutely hate hum or buzz (either mechanical or through speakers) from equipment, and won't tolerate it in my system.  It could be DC on the line, but not necessarily.  Next time you hear the mechanical hum from all mentioned components, try completely unplugging the Cd-player (but leaving everything else still on) and see if this eliminates it.  If not, more things can still be tried here.  Also, I'm curious what you have all that equipment plugged in to (which may also be a contributing factor) - are you using a strip or conditioner, etc?

[Alphonse]

Thanks all.  I do not have any halogen type lights.  Also, NewBuyer, today I tried your suggestion of unplugging the Arcam CD player, but it did not stop the PP300s from humming. 

I am not using a power conditioner or special AV powerstrip.  I have always had each amp and the preamp plugged into their own wall outlets, with the TV, CD player, and Blu-ray player sharing a simple heavy duty home depot type power strip.

Today when I powered up the preamp, amps, and CD player to listen to some music, the amps and CD player had hum, but after a couple hours of play time the hum went away.

Thanks,  Al