This is probably stating the obvious, but be sure to turn up the volume some on your TV to overcome any residual hum that is a part of the TV's circuitry. If you run your headphones at relatively low volume, you may not hear the hum, but when that same signal is fed through another amplifier and played back at a higher volume, hum can become evident. However, that would be too easy a fix.
Also check where your cable is routed. Sometimes if a cable is too close to another power supply, even an AC adapter, hum can be introduced. Finally, the cause is most likely the hardest to fix, that being a ground loop. This is especially likely if your TV is connected to cable TV. It can be further complicated if your computer is connected to a network through an ethernet connection as well. Try disconnecting the cable from your TV while it is on to see if the hum goes away, realizing, of course, this isn't a viable solution. If the hum does go away, you probably have a groundloop. We tend to think that "ground" is "ground" and this just isn't the case. When devices are connected to ground through multiple paths that take different routes, those paths can themselves create what amounts to one turn on a large coil that can pick up hum. Sometimes to correct such a problem you have to actually disconnect a device from ground or isolate devices. Let's take a quick possible example. Let's say that your computer is connected to internet by being plugged into a router that is connected to a cable modem. In addition to normal grounds, there is a ground on the ethernet cable that connects back to the ground of your router, that connects to the ground on your cable modem that connects to the ground or outer shield of the coaxial cable that goes to a splitter where the cable splits and goes to your tv. Now, the ground on your tv is connected to the audio ground on your patch cord which connects to the audio ground on your desktop which is connected to your desktops ground. We have just described a path that makes a long trip that can be described as a loop. If disconnecting the cable from your TV gets rid of the hum, there are filters that can be placed between a TV and a cable that allows the cable's shield to act as a ground for radio and TV signals but not for AC. This would then break this particular loop. Unfortunately, there are other interactions that can cause ground loops so figuring out how to avoid them is a pain. Of course, if you were able to connect your TV to your desktop using bluetooth, there would be no physical connection. This can be done in a number of ways, but the bluetooth sound might be lower quality. You also might consider recording on aa portable audio recorder and then transferring the results to your computer. In the end, you should be able to record directly on your desktop, but depending upon other factors, the hum may not be so easy to eliminate. Maybe, though, you'll be lucky, and turning up the TV's volume a little will clear up everything! Best regards, Steve Jacobson On Wed, 19 Mar 2014 14:17:09 -0400, Dean Masters wrote: >Yes it is to a desktop. All outlets are the three prong type which means >they should be grounded. >Dean >-----Original Message----- >From: Joe Paton >Sent: Wednesday, March 19, 2014 4:15 AM >To: PC Audio Discussion List >Subject: Re: Hum from Cable >Hi, >are you connecting to a desktop computer? >You might try grounding your machine if this is the case. >Joe >On Tue, 18 Mar 2014 21:52:03 -0400 >Dean Masters <dwmaster...@gmail.com> wrote: >I am wanting to run a patch cord from the headphone jack on my TV to my PC >to record some shows but there is a hum. I have Comcast cable. The patch >cord is actuallly two cords with male plugs on both ends and a connector >with two female plugs. >When I put headpohones in the jack there is no hum. >Is there something I can do to get rid of the hum? >Thanks, >Dean >-- >Joe Paton <j...@vi-ability.demon.co.uk>
