[wilsynet]

I recently acquired a new preamp and there's a hum that I hear from the speakers that seems to be related to power quality and the preamp.  When I run direct from DAC (has a digital volume control) to amplifier, there is no hum.  When I put the preamp in the chain, I get hum.  Other preamps I've had in the past have not suffered from this, but its an older house so I suspect the power more than I do the preamp.

As for the hum, it's a medium volume, low frequency hum, a bit like a fog horn.  It'll come and go seemingly with usage of power by other things.

For example, I'll hear the hum for awhile, then I'll switch off the living room lights and then it'll go away.  If I then turn on the TV, the hum comes back.  Or I'll leave the lights on, the hum goes away after a few minutes only to return again 5 minutes later.

I have the preamp plugged into the Balanced Power Technology CPC.  Not one of their balanced isolating transformer based power centers, one of their less expensive CPC units.   I'm wondering if perhaps something more sophisticated would be appropriate.

Also, I'm renting, so I'm reluctant to call an electrician to investigate and fix.  But if that's the best thing to do, I'm somewhat open to it.

Is there a PI Audio Group product that people think would resolve this issue?

Thanks!

[morganc]

Remember all the problems I had?   It was likely a microphonic tube causing mine as well as poor grounding on the amp and preamp that I had.  Could yours be tube related?  You've had so much gear in your house that I doubt this could be an AC issue unless you moved?   

[dBe]

I recently acquired a new preamp and there's a hum that I hear from the speakers that seems to be related to power quality and the preamp.  When I run direct from DAC (has a digital volume control) to amplifier, there is no hum.  When I put the preamp in the chain, I get hum.  Other preamps I've had in the past have not suffered from this, but its an older house so I suspect the power more than I do the preamp.

As for the hum, it's a medium volume, low frequency hum, a bit like a fog horn.  It'll come and go seemingly with usage of power by other things.

For example, I'll hear the hum for awhile, then I'll switch off the living room lights and then it'll go away.  If I then turn on the TV, the hum comes back.  Or I'll leave the lights on, the hum goes away after a few minutes only to return again 5 minutes later.

I have the preamp plugged into the Balanced Power Technology CPC.  Not one of their balanced isolating transformer based power centers, one of their less expensive CPC units.   I'm wondering if perhaps something more sophisticated would be appropriate.

Also, I'm renting, so I'm reluctant to call an electrician to investigate and fix.  But if that's the best thing to do, I'm somewhat open to it.

Is there a PI Audio Group product that people think would resolve this issue?

Thanks!

First, it sounds like there may be a correlation with other things in the house.

Check these first:

Turn off ANY dimmers

If you are using CFL's they "may be" a culprit, but their switching frequency is pretty high for this issue

Make sure your washer/dryer or dishwasher isn't causing the problem = half wave heaters in them

Unplug any 2-prong cords to lamps and whatnot.  Could be there is a loop if they are not polarized properly. Check your TV for this, too.

Make sure your interconnects are away from any power cabling

Start there and check back in before you spend $$$.  I would love to sell you something, but not if there is a simpler reason for the hum'

I hate hum... I hate hummmmmmmmmm........................... ...

Dave

[wilsynet]

I couldn't investigate the past couple of days, but this morning I powered on the system again.

Different day, different problems.  No equipment or household changes other than time has elapsed.

Hum is gone.  Can't get it to come back like I could before.  Switching on lights and TV don't seem to change anything, where before the hum would return if I did these things.

Hum has been replaced by a low volume hiss that comes from all three drivers on both channels.  These are 85 db efficient speakers, not 101 db efficient speakers, and I haven't heard background hiss from them before.  On the woofer, it's more of a woosh than a hiss, and more like a hiss from the midrange and RAAL tweeter.

This noise was not there before, not masked by the hum.  Swapping tubes, turning off or unplugging other equipment, moving interconnects away from power cords, etc, does not make it go away.

Could this be noise on the power line I'm hearing?

[wilsynet]

A hah!  If I turn on the microwave, hum comes back.

Any recommendations for making the system microwave proof?

[fridays]

Don't use a microwave period

[wilsynet]

I haven't had equipment that has been sensitive in this way before, but the house is a pretty old house and I imagine the wiring is pretty old too.  The microwave isn't the only cause of the hum, but it can be one of them.  Would be good to make the system more resilient to noise on the line?

[dBe]

I haven't had equipment that has been sensitive in this way before, but the house is a pretty old house and I imagine the wiring is pretty old too.  The microwave isn't the only cause of the hum, but it can be one of them.  Would be good to make the system more resilient to noise on the line?

Old houses = new problems... and old ones, too.  How old?  2 or 3 conductor receptacles?

Dave

[wilsynet]

House was built in 1940.  I can see old 2 conductor receptacles, but at some point someone added 3 conductor receptacles (which are the ones I'm using).

When the refrigerator cycles on or the clothes dryer starts, the lights dim for a moment and then return.

[satfrat]

House was built in 1940.  I can see old 2 conductor receptacles, but at some point someone added 3 conductor receptacles (which are the ones I'm using).

When the refrigerator cycles on or the clothes dryer starts, the lights dim for a moment and then return.

Sounds just like my house,, which btw I've been renting since 1976. How many circuits do you have available? I only have ancient 2 prong outlets myself. When I got my BPT BP2.5 balance power conditioner, a 3 prong grounded outlet was necessary so I replaced one of the duplex's and ran a green ground wire to the copper water pipes. Then I found out that for some reason, the unused attic power was connected to a 20A breaker so I disconected the attic and had a dedicated circuit installed for my system so now I have 2 grounded duplex's on different circuits for my system tho I have all my essential audio gear on the dedicated circuit connected to a UberBuss that's connected to the BPT that's connected to all my A/V gear.

As for hum,,, I've never really had that problem myself evenb tho I'll always live with a flickering light whenever the fridge kicks on or the water pump kicks on. But I'd take that over hum anyday. 

Cheers,
Robin

[dBe]

House was built in 1940.  I can see old 2 conductor receptacles, but at some point someone added 3 conductor receptacles (which are the ones I'm using).

When the refrigerator cycles on or the clothes dryer starts, the lights dim for a moment and then return.

What I'm wondering is:

Did they just add the receptacles without a ground wire?

Did they get the receptacles wire correctly for polarity?

Send me a PM with your address in it.  I have something for you.

Dave

[Speedskater]

Lots of older World War II era, homes used open wires (Knob & Tube).  Often they did not keep the Hot & Neutral wires together.  They would connect to any handy near-by Neutral wire.  This creates all kinds of problems when Neutral current from one circuit flows through the Neutral of another circuit. So rather than Ground Loops we have Neutral loops all over the house.

[dBe]

Lots of older World War II era, homes used open wires (Knob & Tube).  Often they did not keep the Hot & Neutral wires together.  They would connect to any handy near-by Neutral wire.  This creates all kinds of problems when Neutral current from one circuit flows through the Neutral of another circuit. So rather than Ground Loops we have Neutral loops all over the house.

Out here in the wild west nothing is over 40 years old hardly.  I didn't even think of the neutral loop thing.

Good call.

Dave

[vinyl_lady]

My home in Spokane was built in 1911 and all of the homes in my neighborhood have or had knob & tube wiring. Most of mine was replaced in 1986 by the previous owner. I added an addition in 2005 that his my music room and we did a separate panel for the room with a dedicated 20 amp circuit for all things audio.

[dlbeck]

Reviving this old thread since I was going to title a thread with the same title.  I live in 7 year old house but have had some power related issues like light bulbs don't last very long.  Now the hum in the speakers.  I hate the hum. I have a tube preamp that had a minor issue but also starting to think the power may be the culprit. I believe the outlet I use for all my devices (receiver, amp, preamp, etc) are on the same circuit as a couple lights and maybe the water heater. 

So, should I run a dedicated line from the panel (long ways away) or buy a device that would clean things up.  Electrician said it would be about $1000 to run a dedicated line.

Any thoughts would be appreciated and I'm still reading a lot on AC about people who have encountered similar problems. Thanks.

David

[Speedskater]

Rapidly burning-out light bulbs sometimes is caused by a "Lost Neutral" power problem. "Lost Neutral" means that somewhere between the power company's transformer and your receptacle's there is a poor connection or a high resistance Neutral wire.  This means that under heavy load conditions, your circuits aren't dividing to 120V/120V but maybe something like 140V/100V.

[HAL]

A problem is a possible loose neutral connection at the box or line feed-in.  Had that happen on my mom's old house.  Had the electrical company in to correct the feed and fixed the issue.

One thing that happend here was the connections in the meter base were corroded probably due to a nearby lightning stike.  The local power utility had to come and remove the meter to correct it.  Cause a lot of hum problems in the system.

Just some other things to possibly check.

[dBe]

I think the lost neutral diagnosis is accurate and more than likely the culprit.

Here is what I would do, but ONLY if you are confident that you won't kill yourself trying to do this.  If you are not comfortable working with AC (and potential death) hire a licensed electrician to do this.  Observe all safety precautions: identify and turn off the breaker for the receptacles you are working on  (another plus for this is that if you do not have a properly labeled service entrance you can do so when you are doing the work); wear insulated sole shoes; wearing thin workman's gloves is a good idea: be vewwy, vewwy caweful at all times.

The process is simple -  remove each receptacle, check the wires for discoloration, clean the wires and tighten the snot out of each connection.  Pay special attention to the discoloration of the wires.  A lot of black corrosion means that the wiring was not well tightened.  If you have red corrosion you probably live around salt water and should check them more often.  If you live in a humid area putting a thin coating of No-ox-id A special http://www.sanchem.com/aSpecialE.html or equivalent will prevent most of your problems in the future.  It is electrically conductive and need to be applied very sparingly.  Do NOT use tail lamp grease - that suff is bad ju-ju over the long run.  After you have cleaned up and tightened everything re-install the receptacle and move on.  IF any screw feels even the least bit that it is stripped, move the wire to the adjacent pole, or better yet, replace that receptacle.  This is a PITA, but will probably cure your ills. 

I recommend that you leave the service entrance to an electrician unless you absolutely know what you are doing and feel confident work around 240V that can dump 200A before you can even think  Always - Safety first.

You never mentioned where you live.  If you live in a cold climate, this could be part of the problem, too differential heating between winter and summer can loosen screw more readily.  I check receptacles once a year for tightness.

REMEMBER: SAFETY FIRST.  We don't want to call you Sparky.

While you are at it replace the receptacles that feed your system with some really good ones.  There are a bunch of audiophile (I hate that term) recommended ones available.  I happen to know where you can get some good cryoed ones for not a lot of $$$   

Check back after you have done all of this and let us know the results.  This should cure the problem.  If not, we'll figure something else out.

Dave

[dlbeck]

Thanks guys. I'll give this a try later this week. Btw, I live in Iowa.  Do you think this problem is prevalent through the whole house and by fixing the outlets that I use only for my audio equipment, do you think that would solve the issue?

I should buy some receptacles just to replace them as I do it.  Thanks again.

David

[dBe]

Thanks guys. I'll give this a try later this week. Btw, I live in Iowa.  Do you think this problem is prevalent through the whole house and by fixing the outlets that I use only for my audio equipment, do you think that would solve the issue?

I should buy some receptacles just to replace them as I do it.  Thanks again.

David

David,

I would do the whole house because I'm a glutton for punishment and because if you find one wiring problem in a house you are likely to find more.

The very first thing you should do is go to Harbor Freight, Menards, Lowes, Home Teapot or the like and buy yourself one of these:



I prefer Harbor Freight because their Safety Manager is an AC member and I try to support them.

Check every receptacle in the house to see if they are all good and there isn't a swapped Neutral/Hot issue in one of the plugs.

You will find a lot of uses for this anyway.  It will tell you when the circuit is really off, not just "maybe" off.

Dave