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Astro Spectra Speaker/Audio Question

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MOCOMD1

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SCPD

QRT
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I don't think you can. Some part of the system is going to be grounded. This will kill the radio
 
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MOCOMD1

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Crimping it to a 3.5mm headphone jack and connecting it to my car, would any part be grounded?

What about connecting it to a 6ohm stereo speaker with the + and - n back, how would that be done?
 

SCPD

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The (-) side of the connector or the wiring connected to the jack usually is grounded.
If you connect a speaker to the radio make sure you don't ground anything. Make sure no part of the speaker is grounded to the vehicle's chassis.
 

MOCOMD1

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Thats 20 dollars which i can put towards the other things i need to get like the 800mhz antenna and mount ($35) and the Cable 55 ($15) for the ignition sense and speaker wires.
 

RKG

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You want to go out and learn something about the difference between "balanced audio" and "unbalanced audio." In "unbalanced audio," one lead to the speaker varies in voltage to mimic the shape of the audio wave and the other lead is grounded. In "balanced audio," each lead varies in voltage (usually referenced to a DC bias).

Unbalanced audio is cheaper. Balance audio tends to be more resistant to external interference.

Most car audio systems are unbalanced. Most Motorola two-way radios use balanced audio (at least from the speaker leads; one can obtain unbalanced audio from some radios via an AuxRxOut pin on an accessory connector, but this would be line level audio, insufficient to drive a speaker). If you plug a Motorola two-way into an unbalanced system, it is the same as shorting the two terminals of a battery; a few sparks and then something blows up. What blows up is the very expensive (and possibly no longer available) Motorola audio amplifier in the two-way radio.

Now, there are ways around this. Consult a good radio shop and they could make you an isolation circuit, if the project is worth the expense.
 

ramal121

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I did some looking on Motorola SYNTOR, SYNTOR X, SYNTOR X 9000, SYNTOR X 9000E and SPECTRA Mobile Radio Information for info on my spectra wiring, and found that pin 6 and 7 go to Speaker Hi and Speaker Lo, respectively.

In an effort to save some cash (and with little knowledge on audio) i was wondering if it were possible to simply crimp these two wires into an audio connector such as a 3.5mm stereo jack and play it through my car's aux plug.

Thanks.
Both speaker leads on a Spectra will have a DC bias voltage (put a meter on it and see). Grounding either side will wipe out the audio amp (even if there is no receive audio). This bias voltage could also damage the input of whatever you're trying to plug it into. Unless you isolate the speaker leads with an audio transformer or coupling caps before you plug it into the aux port there will be trouble somewhere. Also, the aux input is expecting line level audio and the Spectra will push out what, 12 watts I think at max. Way too much for the aux input. At least, it will sound crappy. At most, it may wreck the aux input by overdriving it.

Just hang a speaker on it to be cheap and safe. The audio amp is robust and can drive down to a 3.2 ohm speaker although that's pushing it. A 4 ohm speaker is OK, higher is better. A real Moto speaker sounds the best, but anything will work.

For those bent on running a Spectra through a car stereo or whatever, line level audio is available on a pin of the db15 accessory plug. Bummer is you have to jack with a couple of jumpers inside radio to make it fly.
 

lbfd09

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You want to go out and learn something about the difference between "balanced audio" and "unbalanced audio." In "unbalanced audio," one lead to the speaker varies in voltage to mimic the shape of the audio wave and the other lead is grounded. In "balanced audio," each lead varies in voltage (usually referenced to a DC bias).

Unbalanced audio is cheaper. Balance audio tends to be more resistant to external interference.

Most car audio systems are unbalanced. Most Motorola two-way radios use balanced audio (at least from the speaker leads; one can obtain unbalanced audio from some radios via an AuxRxOut pin on an accessory connector, but this would be line level audio, insufficient to drive a speaker). If you plug a Motorola two-way into an unbalanced system, it is the same as shorting the two terminals of a battery; a few sparks and then something blows up. What blows up is the very expensive (and possibly no longer available) Motorola audio amplifier in the two-way radio.

Now, there are ways around this. Consult a good radio shop and they could make you an isolation circuit, if the project is worth the expense.

I came across this from a web search looking to an isolation transformer aka circuit. I have a variation of this problem and need to get the radio audio to an other rack. I keep loosing audio when I connect both sides of the speaker output. From my searching I find that an isolation transformer is all that's required. Hey even that Radio Shack place claims to have them. Hey, miracles never cease to amaze.
 

cmdrwill

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Depending on your "rack" application you can use a 2000 ohm to 600 ohm audio transformer to isolate the balanced speaker output to the rack input for Line level audio.

You will still need a resistor on the speaker leads to keep the bridge audio IC in the radio happy if you do not use the 8 ohm speaker. 18 ohms at two watts works as a 'dummy speaker' load.

If I knew more on the "rack" I can give you a better idea.
 
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