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Telephone PC Interface
I am trying to find a way to record telephone conversations to my PC,
(legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks |
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"Jay" wrote in message om... I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks I suspect the problem is a grounding one. If you plug into the microphone input of your cassette recorder and all works well and then move the plug over to your computer mic input and all you get is hum, then check to see if your 'interface' is powered. If it is, use an isolation transformer or temporarily run it by battery. If it then works, you can sole the problem permanently. |
"Jay" wrote in message om... I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks I suspect the problem is a grounding one. If you plug into the microphone input of your cassette recorder and all works well and then move the plug over to your computer mic input and all you get is hum, then check to see if your 'interface' is powered. If it is, use an isolation transformer or temporarily run it by battery. If it then works, you can sole the problem permanently. |
"Dana Raymond" wrote in message
. cable.rogers.com... "Jay" wrote in message om... I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks I suspect the problem is a grounding one. If you plug into the microphone input of your cassette recorder and all works well and then move the plug over to your computer mic input and all you get is hum, then check to see if your 'interface' is powered. If it is, use an isolation transformer or temporarily run it by battery. If it then works, you can sole the problem permanently. If your in a real hurry take apart an old modem, lots o filter coupling parts, and hey they work with phones. Try running the phone line to a modem(no power to it) and pick the signal off the matching/isolation transformer output use the soundcard line in. With a little post processing to even up levels and some VOX software to conserve disk space I had 100's of hours of conversations. No, I didn't learn much of the subtleties of phone interface circuits but it took only minutes and cost me some old hardware from the junk box. -- They can have my command prompt when they pry it from my cold dead fingers. |
"Dana Raymond" wrote in message
. cable.rogers.com... "Jay" wrote in message om... I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks I suspect the problem is a grounding one. If you plug into the microphone input of your cassette recorder and all works well and then move the plug over to your computer mic input and all you get is hum, then check to see if your 'interface' is powered. If it is, use an isolation transformer or temporarily run it by battery. If it then works, you can sole the problem permanently. If your in a real hurry take apart an old modem, lots o filter coupling parts, and hey they work with phones. Try running the phone line to a modem(no power to it) and pick the signal off the matching/isolation transformer output use the soundcard line in. With a little post processing to even up levels and some VOX software to conserve disk space I had 100's of hours of conversations. No, I didn't learn much of the subtleties of phone interface circuits but it took only minutes and cost me some old hardware from the junk box. -- They can have my command prompt when they pry it from my cold dead fingers. |
Soundcards don't take the same kind of microphones as tape recorders. A
tape recorder or PA system takes a microphone that outputs about 1 mV. A soundcard supplies power through a resistor to a transistor inside the microphone, amplifying the sound level to about 30 mV. A few years ago I published an article and circuit in QST (the ham radio magazine) about how to use a traditional microphone with a soundcard. It's a 1-transistor amplifier. I don't have the circuit or the exact reference handy. |
Soundcards don't take the same kind of microphones as tape recorders. A
tape recorder or PA system takes a microphone that outputs about 1 mV. A soundcard supplies power through a resistor to a transistor inside the microphone, amplifying the sound level to about 30 mV. A few years ago I published an article and circuit in QST (the ham radio magazine) about how to use a traditional microphone with a soundcard. It's a 1-transistor amplifier. I don't have the circuit or the exact reference handy. |
"Jay" wrote in message om... I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks How about this? http://www.modemspy.com/en/index.php -- To reply: Please remove x y z. |
"Jay" wrote in message om... I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks How about this? http://www.modemspy.com/en/index.php -- To reply: Please remove x y z. |
"Michael A. Covington" wrote in message ...
Soundcards don't take the same kind of microphones as tape recorders. A tape recorder or PA system takes a microphone that outputs about 1 mV. A soundcard supplies power through a resistor to a transistor inside the microphone, amplifying the sound level to about 30 mV. A few years ago I published an article and circuit in QST (the ham radio magazine) about how to use a traditional microphone with a soundcard. It's a 1-transistor amplifier. I don't have the circuit or the exact reference handy. Okay, thanks for the advice. Apparently the mike jack isn't compatible with a telephone/cassette interface. What about the line in jack on the back of the computer? Would this be compatible with this type of interface? |
Ischultz posted:
I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? The simple answer is that you must use a transformer. Your telephone line is a "balanced" line. Your sound card has an "unbalanced" input. When you connect between the telephone and the PC's line input using your interface (device) you are essentially placing a ground on one side of the telephone line, unbalancing it and causing it to be a great noise and hum receptor. The interface (device) you now have works with the cassette recorder because the interconnecting cable is short and the cassette recorder is not grounded. If it *were* grounded, it would cause noise and hummmmm too. You cannot fix this by using more capacitors anywhere. You must use a transformer. Tell us more about your interface device and we can help with specific details of the transformer you need. Don |
On 14 Sep 2004 14:43:13 -0700, Jay wrote:
I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks I think some "voicemodems" allowed voice recordings to be played on a telephone line. There may be a model that will do exactly what you want. Aidan Grey |
Aidan Grey wrote:
On 14 Sep 2004 14:43:13 -0700, Jay wrote: I am trying to find a way to record telephone conversations to my PC, (legal, for training purposes only). I have an interface that plugs into a cassette recorder and that works fine on the cassette. I have tried this same interface plugged into my computer, either line-in or the microphone jack, but when I record I get a loud hum noise and I can faintly hear myself in the background, though I have to talk or whistle loudly to do so. Apparantly I need a different interface. I have found them for sale for around $50, but I would prefer to make my on, usually these interfaces use fairly simply filter circuits. Any suggestions? Thanks I think some "voicemodems" allowed voice recordings to be played on a telephone line. There may be a model that will do exactly what you want. Actually that's all under software (ATAPI standard) control. IOW, with the proper program, *all* voice modems.... jak Aidan Grey |
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