As soon as I connect the video in connector of the CRT TV to the STB, I get noise in the amp. The amp is connected to the STB through a Sony stereo. The noise is coupled only if this galvanic connection is made, not electromagnetic coupled.
No, please don't suggest change to Flat TV.
Is there a solution to this problem.
Gajanan Phadte
No, please don't suggest change to Flat TV.
Is there a solution to this problem.
Gajanan Phadte
Do you live in a unit with a shared antenna? Try disconnecting the antenna from the wall socket and see whether the noise goes away. If it does, you probably need to get an isolator.
When an antenna is shared among many units it has an amplifier to boost the signal. The earth potential of that amplifier can be different to that of your system, so when the earth of the antenna is connected to your equipment current flows causing hum/noise.
Tony.
When an antenna is shared among many units it has an amplifier to boost the signal. The earth potential of that amplifier can be different to that of your system, so when the earth of the antenna is connected to your equipment current flows causing hum/noise.
Tony.
It is not shared and is an individual owned DTH system. I was thinking of using audio transformers from old push pull 1 Watt power amp circuits from a tape recorder from the Ge era, isolating the audio gear galvanically. Aim is to just get rid of the annoying noise. Audio may suffer, but it is purely communication audio from the TV.
What I was looking for is to isolate Video galavanically, don't know if it is possible.
Gajanan Phadte
What I was looking for is to isolate Video galavanically, don't know if it is possible.
Gajanan Phadte
Still could be an earth loop, do both the TV and the amp have a three pin power plug?
If so the loop breaker circuit here --> Earthing (Grounding) Your Hi-Fi - Tricks and Techniques may help. Is the noise a 50 Hz Hum/buzz?
Tony.
If so the loop breaker circuit here --> Earthing (Grounding) Your Hi-Fi - Tricks and Techniques may help. Is the noise a 50 Hz Hum/buzz?
Tony.
All are two pin. I have a three pin for the amp but it is not connected to the ground(chasis). Only connected to the RFI mains filter.
Noise is not mains hum.
Gajanan Phadte
Noise is not mains hum.
Gajanan Phadte
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I don't see them in current Bourns catalogs but they look like miniature telecomms. balanced line transformers - perhaps from a fax, ethernet, modem or such. Probably ferrite core, narrow bandwidth and not too linear.
If this noise is actually higher frequency and you hear a sub-harmonic, perhaps it's worth looking at the noise frequency on a borrowed instrument - even a scope and consider a filter for that interference. 15.625 kHz was a pest with misaligned oscillators locally - maybe worth checking.
If this noise is actually higher frequency and you hear a sub-harmonic, perhaps it's worth looking at the noise frequency on a borrowed instrument - even a scope and consider a filter for that interference. 15.625 kHz was a pest with misaligned oscillators locally - maybe worth checking.
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those will work just fine for 2V signals. sorry, edit: those hava a 10k winding and a 500R winding.... if you have 4 of them you can connect the 500R windings on two transfomers so you have ... audio in connected to a 10k winding 500R winding of the first transformer connected in parallel with the 500R winding, and the ouput taken from the 10k winding of the second transformer, so for 2 channel audio, you need 4 transformers.
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They are miniature about 1 cm on one side.
The transformers are pulled from an echosounder signal receiver/amplifier card. The sounder was dual freq and the freqs were 33KHz and 210KHz.
Unclejed613
What I understand is dual isolation for unity voltage gain. I have more of these, so will give a try.
Gajanan Phadte
The transformers are pulled from an echosounder signal receiver/amplifier card. The sounder was dual freq and the freqs were 33KHz and 210KHz.
Unclejed613
What I understand is dual isolation for unity voltage gain. I have more of these, so will give a try.
Gajanan Phadte
This noise follows/change with the picture/frame. So it is probably a cross talk inside the circuitry between audio and video.
Gajanan Phadte
The blue trafos at post#6 cannot be used as they are having a frequency response from about 7KHz to above 20KHz and 500ohms coil seem to be the input(primary) side.
Gajanan Phadte
Gajanan Phadte
To have an audio transformer with good bandwidth, you'll need a moderately expensive item. It should be shielded with steel or mu-metal for best results inside an electrically noisy TV.
However, because TV isolation voltage standards are for much higher voltage than a cheap audio transformer will have, this is still considered very dangerous for live or isolated chassis TVs. However, I'm no safety expert nor am I familiar with your local appliance safety regulations.
However, you can experiment with standard interstage transformers from old transistor radios and small amplifiers. Here's some local examples that you may also obtain cheaper at your usual suppliers or from an old radio, even.
Altronics - Transformers - Audio Coupling
However, because TV isolation voltage standards are for much higher voltage than a cheap audio transformer will have, this is still considered very dangerous for live or isolated chassis TVs. However, I'm no safety expert nor am I familiar with your local appliance safety regulations.
However, you can experiment with standard interstage transformers from old transistor radios and small amplifiers. Here's some local examples that you may also obtain cheaper at your usual suppliers or from an old radio, even.
Altronics - Transformers - Audio Coupling
Does the noise increase when the screen has more white on it? I had this problem when I connected an amplifier to a CRT TV.
I could somehow mostly remedy the problem by switching from a regular RCA cable into a component video cable (which is the same thing, but tends to have much thicker shielding).
Also, moving the wiring as far away from the antenna cord would help to some degree, as well.
Interestingly, I've had none of these problems with my new LED TV. I'm not suggesting a change, though. 😉 I miss the CRT for some reasons, and only switched over because it died on me.
I could somehow mostly remedy the problem by switching from a regular RCA cable into a component video cable (which is the same thing, but tends to have much thicker shielding).
Also, moving the wiring as far away from the antenna cord would help to some degree, as well.
Interestingly, I've had none of these problems with my new LED TV. I'm not suggesting a change, though. 😉 I miss the CRT for some reasons, and only switched over because it died on me.
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