Thanks nigelwright7557. I'm not sure I'd want to take the TV or cable box apart (the box being owned by Virgin Media!), so that leaves the sub. I'm not sure where zero volts is connected to earth in there, or how to find such a connection.
I have a ground loop breaker, but it's not 100% effective (see post #30).
I have a ground loop breaker, but it's not 100% effective (see post #30).
the bass filtering of a transformer is not fixed like an RC high pass filter.
The level of attenuation of the bass is very dependent on the signal level.
The lower the signal level, the less the attenuation.
But the signal between the TV and the audio system is always at the same "line level". Maybe maximum of around 1Vac to 2Vac and average of around 100mVac to 200mVac.
You can measure this at the TV output sockets.
The level of attenuation of the bass is very dependent on the signal level.
The lower the signal level, the less the attenuation.
But the signal between the TV and the audio system is always at the same "line level". Maybe maximum of around 1Vac to 2Vac and average of around 100mVac to 200mVac.
You can measure this at the TV output sockets.
Not in this case. It's varied so that the TV remote still controls the level. The TV is acting like a preamp.
OK, that gives you room for experimentation.
Turn the TV up to max and turn the Audio system down low.
What does that do to the bass levels?
Now go in the opposite direction, turn the TV down and the Audio system up.
Can you hear any difference in bass levels?
Careful to avoid overload distortion at the extremes. Noise may become a problem with the second trial.
Turn the TV up to max and turn the Audio system down low.
What does that do to the bass levels?
Now go in the opposite direction, turn the TV down and the Audio system up.
Can you hear any difference in bass levels?
Careful to avoid overload distortion at the extremes. Noise may become a problem with the second trial.
That is your best bet. CPC used to sell a cylindrical isolator with f connector each side. They may still do.
Forget messing about inside your TV or other equipment. To prove it is a cable earth potential difference problem simply disconnect the cable into the virgin box and I bet the problem goes away. Then effect the cure with an isolating transformer.
The ground loop isolator you already have is not 100% effective because the cable potential difference is polluting your house earth. The proper isolator will prevent that.
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the Virgin cable connection is a very high frequency connection. It can go via a transformer.
But it will work with a capacitor coupling between the Cable entry and the TV. It may have to go between the Virgin box and the TV or it may work between the cable entry and the Virgin box.
Both sides of the signal connection need a coupling capacitor, not just the Signal Flow.
These capacitor coupling adaptors are usually much cheaper than the transformer type adaptor.
But it will work with a capacitor coupling between the Cable entry and the TV. It may have to go between the Virgin box and the TV or it may work between the cable entry and the Virgin box.
Both sides of the signal connection need a coupling capacitor, not just the Signal Flow.
These capacitor coupling adaptors are usually much cheaper than the transformer type adaptor.
All very interesting.
I think a key distinction is whether your cable is "analogue" or higher frequency such as "digital" or satellite. The inexpensive Parts Express isolator might work for some settings or maybe one very slightly more expensive to handle higher frequency services.
Pity Behringer doesn't supply definitive audio specs on their gizmo. And they have odd connectors.
I'm going to stick those little isolation transformers from Edcor into any future projects of mine. Maybe at both ends of the device, eh.
Regarding cable hum, best fix is an antenna! It will greatly improve picture quality. No special trouble getting FM and TV 80 miles.
Ben
I think a key distinction is whether your cable is "analogue" or higher frequency such as "digital" or satellite. The inexpensive Parts Express isolator might work for some settings or maybe one very slightly more expensive to handle higher frequency services.
Pity Behringer doesn't supply definitive audio specs on their gizmo. And they have odd connectors.
I'm going to stick those little isolation transformers from Edcor into any future projects of mine. Maybe at both ends of the device, eh.
Regarding cable hum, best fix is an antenna! It will greatly improve picture quality. No special trouble getting FM and TV 80 miles.
Ben
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