I want to add a MUTE button or switch to a couple of external speakers. If I just install a basic On/Off switch in series with the speaker wire will it do any harm to the scanner's audio circuit to leave that line to the external speaker load open with no load? Or do I need a SPST switch that inserts a resistor load to the scanner while the normal speaker's 8 ohm load is removed?
Adding a MUTE button/switch to an external speaker?
- Thread starter iMONITOR
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doctordialtone
Member
No.
A switch is no different than unplugging the speaker.
A switch is no different than unplugging the speaker.
When you unplug an external speaker there is a contact in the external speaker jack that puts the internal 8 ohm speaker load back into the circuit maintaining the load on the audio amplifier circuit.
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Wouldn't you want a DPDT, then?
common to the radio, 1 pole to speaker, other pole to 8 ohm load?
Its ok, I was picking up what you were laying down.Absolutely, that's what I meant to say. Need more coffee!
Actually a SPDT would work:
Why the 8 ohm resistor? If that's a dummy load (unknown reason) for duplicating the speaker impedance. Impedance is not the the same as resistance as you know.
What program did you use to draw that?
True but I don't know a way to subsitute 8 ohm impedance so I though a resistor would be better than an open circuit. Maybe I'm worrying about nothing. I just remember years ago if you had no load on the output of some amplifiers you could burn them out.
I just found this browser based diagram program today. It's pretty cool and easy to use.
Circuit Diagram Web Editor
Create electronic circuit diagrams online in your browser with the Circuit Diagram Web Editor.
www.circuit-diagram.org
I'm just trying to find a quick and simple to mute my scanners when I get a phone call or the wife is me from the kitchen!
I don't want to put unnecessary wear and tear on the volume controls on my scanners.
I don't want to put unnecessary wear and tear on the volume controls on my scanners.
I don't know either. My theory training was 40 years ago. I just know RF needs a load else the reflected power can damage the finals.
Thank you very much.I just found this browser based diagram program today. It's pretty cool and easy to use.
Circuit Diagram Web Editor
Create electronic circuit diagrams online in your browser with the Circuit Diagram Web Editor.www.circuit-diagram.org
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I didn't even save the sketch, I just did a cut & paste into the forum.
You're welcome and thank you also.
Ubbe
Member
Modern amplifiers are protected in every way. Old designs from the 80's could have some self oscillation problems when run without a load.
But with one switch at each speaker, wouldn't it be the same to just push the menu button on each scanner, or turn down their volume?
Put a relay inside each speaker and power the relays from the same power source through one common mute switch. There's Y split connectors for scanner power plugs that can be used as the power source.
/Ubbe
But with one switch at each speaker, wouldn't it be the same to just push the menu button on each scanner, or turn down their volume?
Put a relay inside each speaker and power the relays from the same power source through one common mute switch. There's Y split connectors for scanner power plugs that can be used as the power source.
/Ubbe
doctordialtone
Member
I just turn the volume down when I go to bed.
I didn't need RadioReference to dream up that solution.
No wear and tear on the hardware and no solder or schematic required.
I didn't need RadioReference to dream up that solution.
No wear and tear on the hardware and no solder or schematic required.
As mentioned in post #10 my goal is not to wear out the controls on the scanner. The volume controls on some Uniden scanners aren't as robust as they used to be.
Ubbe
Member
It's just that big dial wheel on the mobile scanners and the multi function dial on the portables that have mechanical switches that are made of questionable material. The Vol and SQ on the mobiles are just plain carbon pots with an external mechanical raster and I haven't seen any problem with those. The key buttons should also work "forever" and not wear out.
/Ubbe
/Ubbe
If the volume control is just a standard potentiometer how does it sequence the numbers on the display that shows what level it's set at? I was thinking it was one of those cheap rotary switch/mechanical encoder type controllers.
Project4
Member
iMonitor, Your SPDT circuit with the 8 ohm resistor is perfect. If you want to avoid unloading the amplifier during the switch transition you'll need a "make before break" switch. If you can get the receiver's schematic, you can verify if your scanner's audio amplifier has any existing output protection. Please post a photo of your completed project.
Talk about a solution in search of a problem...
If your scanner somehow features a tube amplifier, then yes, you absolutely must maintain the appropriate load.
But I'm guessing you have a more modern device with an amplifier in which no current flows and nothing oscillates when there's nothing connected to the output. Open circuit = nothing is happening = don't worry about it.
If your scanner somehow features a tube amplifier, then yes, you absolutely must maintain the appropriate load.
But I'm guessing you have a more modern device with an amplifier in which no current flows and nothing oscillates when there's nothing connected to the output. Open circuit = nothing is happening = don't worry about it.
Ubbe
Member
It's an analog pot giving a voltage to the CPU's A/D input pin. So there's no audio going thru the pot.
/Ubbe
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