iSonic ES2 loud hum in AUX

engrpas

There is a fairly severe hum from the speakers when the AUX port is connected to an HDTV mounted directly above the radio. Here are the circumstances and some of my findings:
- the TV's analog audio output is connected to the AUX input of the radio with shielded cable with RCA plugs
- the hum is present whether TV is turned on or off, as long as audio cable is connected
- hum starts around mid-level volume and increases as volume is increased beyond that point
- there is no hum when the AUX cable is disconnected from the TV, but the other end still connected to the radio
- when an iPod is in the dock, and the source is set to iPod, the sound is perfect (no hum)
- when the same iPod is connected via audio cables to the AUX input of the radio and the source is set to AUX, the sound is perfect (no hum)
- both TV and radio AC power are plugged into same receptacle
- when attaching a headphone to analog output of TV (same source as the AUX input to the radio), there is no hum
I have been suspecting a ground loop, especially since the isonic has a power cube. Is it possible that the chassis of the isonic is not adequately grounded through the power cube to the AC receptacle? Any thoughts?
Thanks
Pete

dubradio

There is a fairly severe hum from the speakers when the AUX port is connected to an HDTV mounted directly above the radio. Here are the circumstances and some of my findings:
- the TV's analog audio output is connected to the AUX input of the radio with shielded cable with RCA plugs
- the hum is present whether TV is turned on or off, as long as audio cable is connected
- hum starts around mid-level volume and increases as volume is increased beyond that point
- there is no hum when the AUX cable is disconnected from the TV, but the other end still connected to the radio
- when an iPod is in the dock, and the source is set to iPod, the sound is perfect (no hum)
- when the same iPod is connected via audio cables to the AUX input of the radio and the source is set to AUX, the sound is perfect (no hum)
- both TV and radio AC power are plugged into same receptacle
- when attaching a headphone to analog output of TV (same source as the AUX input to the radio), there is no hum
I have been suspecting a ground loop, especially since the isonic has a power cube. Is it possible that the chassis of the isonic is not adequately grounded through the power cube to the AC receptacle? Any thoughts?
Thanks
Pete

Pete,
The issue you are experiencing is caused by a ground loop, but the grounding loop may be more of an issue of the TV causing the problem rather than the Isonic. Quick test....

Connect 2 other devices if possible (1 at a time obviously) either DVD player, Cable box, satilite box, video game system. Basically anything with RCA out and connected to AC power.

If the hum stops when connecting any of these other devices... tada you have isolated the issue to the TV.

If the hum continues on the 2 other devices (which I highly doubt will occur) than the IES2 is the culprit. I personally have never had an issue with the isonic2 experiencing a ground loop though.

To combat any ground loop simply pickup a ground loop isolator


-Kyle

BeefJerky

The ground loop is most likely caused by the cable connection. It is very common, and I've had the same issue. That means the hum will occur when any device is connected to your iSonic that is also connected to a cable line. This could be a TV, cable box, VCR or even DVD recorder.

Since you can have other devices besides your TVplugged into the AUX without a hum, it seems that it is definitely the cable ground that is causing the loop. Unfortunately, a good solution isn't necessarily inexpensive. This is what you need:
http://cgi.ebay.com/CABLE-TV-GROUND-LOOP-ISOLATOR-JENSEN-ISO-MAX-VRD-1FF_W0QQitemZ380190677882QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5885215b7a

This is the only device I've come across that will completely eliminate it without affecting anything else. The cheaper cable line ground loop isolators will give you problems with digital cable and video on demand. I say this from experience, as I have been there and done that. I also don't recommend the in-line RCA audio isolators, as all the ones I've come across will deteriorate the sound quality.

Note that I am *not* affiliated with the manufacturer or seller of this product. I am simply a very satisfied customer since it completely fixed my problem.

headrott

How common is it to have a hum caused by a satellite system? (i.e DirecTV).

Greg

engrpas

I think you guys nailed it. I don't have any input device handy other than an iPod which does is not plugged into AC, but just pulling out the cable from the TV stops the hum. I'll see if Comcast will provide a filter.
Many thanks for the tips
Pete

engrpas

Here is my solution - not the most elegant, not probably to code, but it works ...
I spent a day following all the grounding from the cable box outside the house to all the rooms with cable outlets - could not find anything wrong. I didn't want to use a filter as that would most likely attenuate the signal.

So I just ran an insulated #14 wire from an outlet ground to a coax cable terminal by adding a nut under the cable termination to secure the wire. The hum is gone, essentially the ground loop goes down that wire instead of the amplifier.

dcat

When my tuner went into the shop I moved the Isonic into the living room. (The transformer somehow was injured in the move and Polk replaced it in like 2 days. Fantastic customer service!).

I have TWC cable. Hooking up the analog audio cables from TWC's box to the aux resulted in a hum that was louder than the TV audio. However, hooking the CD player up to the aux resulted in crisp clear sound. After much fiddling I used an old $1 three-to-two prong adapter attached to an extension cord, to try a socket in another room in the apartment. Later I realized it was the adapter and not the distant socket that was removing the hum.

Currently I have the adapter attached to the Isonic and plugged into my J15 power conditioner/UPC, which is plugged into a ground. I mention this because I don't believe that using an adapter is safe, electrically speaking, in most other situations. The few web sites I've just looked at don't recommend this as a solution, but seeing as I didn't even know this was an option, I wanted to get the word out. I plan on using this setup, through my power conditioned UPC, until my tuner is repaired in about a week. I assume the conditoner/spike eliminator/UPC will serve a similar function as the ground but??

BeefJerky

You are correct, it is not safe to be using a cheater plug like that. What you need to do is remove the real source of the ground loop issue - your cable line. This happens when the cable line is not grounded to the same place that your electrical lines are. Current code requires them to have the same ground, but older buildings may not be wired that way.

Here's what you need:
http://cgi.ebay.com/Cable-TV-Ground-Loop-Isolator-Jensen-ISO-MAX-VRD-1FF-/120416399884?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item1c0960720c
(I am not affiliated with that eBay seller in any way. I'm just using this as an example.

No, it is not cheap, but it works 100%, and doesn't affect the strength of your cable signal like the less expensive ones. I have it, and recommend it in cases like this.

dcat

BeefJerky wrote: »

You are correct, it is not safe to be using a cheater plug like that. What you need to do is remove the real source of the ground loop issue - your cable line. This happens when the cable line is not grounded to the same place that your electrical lines are. Current code requires them to have the same ground, but older buildings may not be wired that way.


I readily admit my complete lack of knowledge in this area. Would you tell me please why plugging an adapter into a socket such as this one is bad - keep in mind that the socket in question is in the back of my power conditioner, which is itself not only grounded but wired to prevent surges, spikes and other electrical baddies. This is not a power strip - it weighs 47 pounds (21.36kg)! It's the APC J15 - a google search'll give you more on it if you're curious.

By the way, my building IS very old - built in 1901, I believe, it currently has 36 apartments in it!

Thanks, I seriously am curious, darn this typing for forthright emotions :-)

BeefJerky

Simply put, if your device has the ground plug there is a reason for it. Yes, your power conditioner may still be grounded, but that particular device is not. This could cause parts of that device to be "live" that shouldn't be, even if the device is functioning properly. This not only presents a shock hazard, but possibly a fire hazard. Now that you know the risks, you can decide what to do with that knowledge.