# diagnosing system hum



## TucsonHiFiGuy (Feb 23, 2013)

I've got an emotiva umc200/upa500 combination. When I first set it up about a year ago I remember testing it by turning it up to full volume with nothing playing and there was not a hint of hum in the system. Recently though I have noticed a pretty obvious hum coming from all 5 speakers. I first noticed it after I switched to cable from direc tv. My first thought was to disconnect the hdmi/unplug power from the cable box but when I did that the hum was still there. It occurs on all inputs, does not change when the volume is changed, and goes away if I disconnect the interconnects between the pre amp and amp. The hum remains if I turn off the pre amp but the amp is on

Anyone have any thoughts? I'm considering tearing the whole system apart and putting it back together piece by piece to try and see what may be causing this.


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## chashint (Jan 12, 2011)

With the preamp plugged into the amp and hum present, I would try disconnecting the inputs to the preamp one at a time and see if the hum goes away, if yes leave the offending device unplugged and plug the rest of the inputs back in to make sure there was not two problems.
If all inputs to the preamp are disconnected and you get humm then at least you know the problem is between the amp/preamp.
When you connect the preamp to the amp does the humm start with the first speaker connection ?
If yes does the humm only come out of that speaker or does it come out of all speakers ?


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## tonyvdb (Sep 5, 2007)

Quite often hum can come in from a cable or satellite receiver if one is connected to your system.


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## TucsonHiFiGuy (Feb 23, 2013)

The hum is present with no inputs connected. If i dissonnect/reconnect the interconnects between the preamp/amp, the hum will only be coming through speakers that are connected.


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## chashint (Jan 12, 2011)

Are you connecting the preamp to the amp with RCA plugs or balanced connectors ?


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## chashint (Jan 12, 2011)

I came across this on another forum, don't know if Emotiva has a capacitor problem or not, but it was mentioned in this post

[quote name="cc999" url="/t/1423584/outlaw-975/420#post_24332762"]I can say the following from experience. I owned the UMC-200 for about a year and 3 months. There were alot of problems with it. First off the video switching is terrible. I can't tell you how many time watching TV the sound would drop and come back because of the source audio format changing. Very annoying. Software updates are a complete nightmare. My unit has gone back for repair as now it does not turn on and then all of a sudden after several turn ons it does turn on to a software bootloop. Called Emotive and they admitted to faulty capacitors and power packs on the unit. When you try to mention this on the Emotiva boards you get shut down pretty quickly.
CC[/quote]

I don't have a horse in this race, I am just trying to give you ideas to consider about your hum issue.


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## kevin360 (Oct 4, 2012)

Have you unplugged the RF cable from the cable box? If that is the source of your hum, you'll need an isolation device like this one.

http://www.ebay.com/itm/like/360460878489?lpid=82


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