Pro-163 outputs in mono?

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Brandenburg

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So I just swapped my Pro-164 for a Pro-163 so I could do everything more conviently from my desktop. With the 164, I ran an audio cable from the radio to the line-in on my computer sound card and all was well - in fact, there was very little hum. It was a good setup.

I tried doing the same with the Pro-163, but now the audio is mono (i.e., only getting one ear in my computer headphones to work). I'm connecting from the back of the radio via the EXT SP plug. I tried also, for the fun of it, to connect via the headphone jack at the front of the radio, but I got an insane amount of hum.

Any ideas how I can output my audio from the Pro-163 either as stereo or at least fake stereo (i.e., mono coming through channels A & B on my headphones)? I really hate listening to audio with one ear only :)

Thanks!!
Dan

Oh...and this site rocks. I'm a noob, but I've learned so much already!
 

gmclam

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PRO-163 or PSR-400

The headphone jack does not have a ground, and that will create a ground loop and hum. The ext sp jack does have a ground and is the output to use. If you still get a hum, I'd suggest using an isolation transformer, that's what I did/do.

Because I am using a transfomer, I also wired it to attenuate the signal. I then used the mic input instead of the line input. Mic inputs are mono and most line inputs are stereo. This resolved that issue too.
 

Brandenburg

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Thanks...I'm definately not getting a hum out of the EXT SP jack and that's the one I am using. I have the EXT SP going into the computer's line-in...and it's becoming mono.
 

N8IAA

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Thanks...I'm definately not getting a hum out of the EXT SP jack and that's the one I am using. I have the EXT SP going into the computer's line-in...and it's becoming mono.
Being that it is a RS model, use a stereo to stereo adapter and see if that solves the problem. RS does sell a cable that has the transformer in it. That would be your next solution.
Larry
 

Brandenburg

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Being that it is a RS model, use a stereo to stereo adapter and see if that solves the problem. RS does sell a cable that has the transformer in it. That would be your next solution.
Larry

Awesome...thanks. I'll check into both those options. I appreciate it!
 

gmclam

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and it's becoming mono.
Perhaps I misunderstood what you meant here. The scanner is not stereo and only has one audio source. You can't make it stereo. When I first read this I took it to mean that it is working correctly. Now I think you meant that you are only hearing audio on one channel, and you want to hear it on both.

By using the mic input, the computer will route the mono input to both left and right channels. There is a pan control in the mixer if you need to alter one side or the other.

To make the line input work, you'll need a cable or set of adapters that are mono on the scanner end, and stereo on the PC end. Of course it will need to connect the two signal inputs on the PC end together, and that takes an adapter (unless you make your own cable).
 

KC5EIB

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The headphone jacks on the 163 and 164 are wired such that mono or stereo headphones will work. The Ext Sp on the 163 is wired for mono only. You can use a mono to stereo adapter ot use the headphone jack on the 163 like you did with the 164
 

gmclam

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PRO-164/PSR-300 headphone audio

The headphone jacks on the 163 and 164 are wired such that mono or stereo headphones will work.
Yes they did, which is why there is no ground on the connector. It works great for headphones, but is lousy when connected to a computer.
 

KC5EIB

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There is a ground on the connector. Its just that the ground has a resistor in it to limit the audio level to the headphones. Run a lead from the sleve of the headphone hack to the antenna ground to bypass the resistor.
 

gmclam

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There is a ground on the connector.
There is NOT.

It's just that the ground has a resistor in it to limit the audio level to the headphones.
What do you think the resistors on the other side of the audio do?

Run a lead from the sleve of the headphone hack to the antenna ground to bypass the resistor.
Yup, and in most cases this will eliminate the hum you have, because otherwise there is no ground.
 

KC5EIB

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There IS a ground on the headphone jack, its just not a chassis level ground. The audio circuits of the radio are happy with the resistive ground. As far as the resistors on the plus side of the audio circuit, they are most likely for bias or impedance matching.
 

gmclam

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Hand-held scanners headphone Jack

As you can see from the attached schematic portion, the headphone jack does NOT have a ground, either a chassis ground nor a circuit ground, connected to it.

The tip of the jack connects through a 1uH choke to the audio amplifier output. When nothing is plugged in to the jack, the audio output connects directly to the speaker, and the other side of the speaker connects directly to ground.

The ring of the jack connects through a 68 ohm resistor to ground. More on that in a moment.

The sleeve ("ground") of the jack connects through a whopping 470 ohm resistor to ground.

When a stereo headset is plugged in, unless it is very high impedance, its 'speakers' are essentially connected in series from the audio amplifier output, the 68 ohm resistor and ground. The 470 ohm resistor would not have much affect unless the headphone has a 'high' impedance.

When a mono headset is plugged in to the jack, the sleeve and ring would be shorted, resulting in a little less than 68 ohms to ground on one side, and the other going to the audio amplifier.

The 'problem' is when this jack is used to feed a computer. A typical computer has connections to ground via power, network connections and other means. But because there is no direct ground to the audio source (the scanner), there is often a hum. Using the negative power connection or shield side of the antenna (which are direct grounds) of the scanner as the ground side of the audio will significantly reduce the hum. For some this is not enough and an isolation transformer is a better choice.

On the base scanners such as PRO-163 or PSR-400, there is an EXT SP jack. It is a MONO jack, there are no resistors involved. It has a direct ground and 'direct' connection to the audio amplifier output. MUCH BETTER for connection to sound card inputs, regardless of whether or not a transformer is used.

I am using transformers here because I also need to drop the signal level for use with a sound card mic input (it does not have a line input).
 

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