?
Solved

LCD TVs - What would generate a 1110Hz (audio) pitch?

Posted on 2014-03-28
2
Medium Priority
?
222 Views
Last Modified: 2014-04-16
We have a new soundbar ($200 range, middle of the road as these things go).
Unrelated, due to various factors we must use the Earphone-out jack from the TVs.
We realize that this is not optimal impedance matching, but it's not a high-end home theater situation.

What about two different brands of flatscreen TVs (Sceptre, LG) would BOTH generate the identical 1110Hz pitch picked up by the soundbar amp/spkr?
Is there an internal scan line frequency or refresh rate that coincidentally is the same in both TVs?  (maybe a uproc or switching pwr supply  clock frequency?) -- something whose EM field is unshielded or un-notch-filtered.
I've tried all combinations of off/unplugged, and it's only when the one isolated TV under test (connected to the soundbar) is plugged in that the pitch is picked up WHETHER THE TV IS "ON" of "OFF" (i suspect a standby mode). Also, it's the same regardless of TV input source selected (HDMI vs AUX vs TV RF tuner).  Also high-end earphones pick up nothing.

In trying another non-TV device earphone-output jack (my laptop was handiest), there is no pitch (i would have expected the laptop to have more rogue unfiltered/unshielded emissions going on),  thus it's not the soundbar's fault.

We can live with the SNR mitigated with TV volume loud and soundbar volume low, there's no distortion.

But i'm curious why exactly 1110Hz,  between two brands.
0
Comment
Question by:willsherwood
2 Comments
 
LVL 22

Accepted Solution

by:
CompProbSolv earned 2000 total points
ID: 39962817
My first suspicion is some sort of grounding problem.  Headphone jacks are typically designed to connect to passive devices that have no ground (or other power) connections.  That would explain why headphones or a battery-powered laptop wouldn't exhibit the problem.

I'm afraid that I can't explain the actual frequency.  My first guess would be that it has to do with the switching power supply in the TV, but I believe that those run at much higher frequencies than that.

Is there any chance you can use a different output, such as line-level or optical?  If not, some sort of audio isolator may be appropriate.
0
 

Author Comment

by:willsherwood
ID: 39962860
thanks for your comments- the optical output jack for the TV is broken (we didn't discover until too many months too late), i suspect it would be fine.
i hear you about passive... (low impedance)
0

Featured Post

VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

by Todd L'Herrou An important part of the home theater experience is surround sound. Surround sound is the use of multiple speakers to create a 3D ambiance of sound - so that does that mean? Well, simply put, surround sound is what makes it sound…
I don't watch much broadcast TV directly (I hate commercials), but I do have an extensive library of video files (movies and TV episodes) on my PC's hard disk.  When I got my new Toshiba HDTV, the first thing I did was hook up the "PC Interface" as …
Screencast - Getting to Know the Pipeline
Kernel Data Recovery is a renowned Data Recovery solution provider which offers wide range of softwares for both enterprise and home users with its cost-effective solutions. Let's have a quick overview of the journey and data recovery tools range he…
Suggested Courses

578 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question