Splitting Audio to Speaker & FM Transmitter - AVS Forum
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post #1 of 14 Old 12-12-2012, 09:23 AM - Thread Starter
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Is it 'Possible' or 'How do you Accomplish' Splitting Audio Signal/Feed from a 'Ear Phone Jack' to a Speaker and FM transmitter at the same time without having the Speaker get Muted?

The Background: I have a Mr. Christmas Light & Show Music Generator/Unit that featured an enclosed Audio Speaker that I accessed & eliminated and re routed the Positive/Negative wires to Dual External Ear Phone Jacks on the Case, to feed to a Remote Speaker instead; and to feed a FM Transmitter, so I could Broadcast the Music to people walking and Broadcast at the same time to passing Motorists; the Problem exists that when I plug in the FM Transmitter in, it Mutes the Speaker, I want to be able to have the Speaker and FM Transmitter work at the same time.

Thanks, Doug.
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post #2 of 14 Old 12-12-2012, 09:32 AM
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re routed the Positive/Negative wires to Dual External Ear Phone Jacks on the Case

How, exactly, did you wire this?

Does the device have one speaker or two?
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post #3 of 14 Old 12-12-2012, 09:42 AM - Thread Starter
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The Unit had one Speaker, I identified the Polarity and cut the wires and re-wired into a' Y' to feed to 2 Ear Phone Jacks, which were Stereo Jacks; which I made into Mono by sodering/bridging both positve terminals of the Jack, not sure if I should have done this or just sodered onto the Positve/Mono terminal only?

My plan was to have 2 Jacks, one for the Remote Speaker and the second for the FM transmitter.
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post #4 of 14 Old 12-12-2012, 09:47 AM
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If you plug a two conductor plug into a 3 conductor jack, which has the tip and ring soLdered together, you will short the signal to ground.

The other problem is that the signal is meant to drive a low impedance speaker, it will be too hot for the high impedance line input on the transmitter. Use a voltage divider on this output.
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post #5 of 14 Old 12-12-2012, 09:56 AM - Thread Starter
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Appreciate the reply; So, to possible make this work; Use' 2 Conductor Only' Plugs and Jacks; then use a 'VOLTAGE DIVIDER' on the line going to the FM Transmitter or going to the FM Transmitter Ear Phone Jack?

Not Familar with Votage Divders? are they the same as Voltage regulators? Can you lead me in the right direction as to the correct one to use for what I am trying to accomplish? Possible Source?

Thanks a bunch. Doug.
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post #6 of 14 Old 12-12-2012, 10:04 AM
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post #7 of 14 Old 12-12-2012, 10:18 AM - Thread Starter
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I gather that a Voltage Divider is something that I have to Fabricate, in the Attached diagram; where would I attach the Audio wires from the source? I can see Speaker Out would imply going to the remote Speaker, and I'm presuming Line Out would go to the FM Transmitter.

Would I attach the 'Positive Audio Wire' to the connection/union between R1/10K & R2/1K and the 'Negative Audio Wire' to connection/union between SPEAKER GND & LINE GND

Thanks for the help, I thought I was doomed. Doug.

Also, the listed Resistors would work for my Application?
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post #8 of 14 Old 12-12-2012, 10:56 AM
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The source connects to "speaker out", since the source is supposed to drive a speaker.

The "line out", in this example, would be about 1/11 of the source voltage.

you could replace the two resistors with a potentiometer and have a variable output.
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post #9 of 14 Old 12-12-2012, 11:18 AM - Thread Starter
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I sure appreciate your Help.

So to Clarify;

In my application, I would keep the dual leads/wires that I created coming from the Audio Source or what used to feed the enclosed Speaker. One set of leads or wires (Positive & Negative) would feed the remote Speaker through the Ear Phone Jack I have intalled; the other set of Wires(also, Positive & Negative) would feed through the Voltage Divider, attached first to the 'Speaker Out Side'; Positive to the SPEAKER OUT and Negative to the SPEAKER GND.

I would then run a wire from the 'LINE OUT' to the 'Ear Phone Jack Positve Terminal' and another wire from the LINE GND to the 'Ear Phone Jack Negative Terminal'; Plug in the FM Transmitter and both the Speaker and FM Transmitter should work!

Would this be correct?

Thanks, Doug.
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post #10 of 14 Old 12-12-2012, 11:21 AM - Thread Starter
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Quote:
Originally Posted by SAM64 View Post

you could replace the two resistors with a potentiometer and have a variable output.

Any Advantages to Potentiometer vs Resistors?

On that link you provided they mentioned Replacing R2 with a 1 kohm trimmer?
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post #11 of 14 Old 12-12-2012, 11:41 AM
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Quote:
Would this be correct?

Yes.
Quote:
Any Advantages to Potentiometer vs Resistors?

A pot allows you to vary the output level to the transmitter.
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post #12 of 14 Old 12-12-2012, 01:07 PM
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Given the fact that you are starting with a speaker level signal, I would substitute the 10k dropping resistor with a 100k resistor. We use a 100k linear taper pot for a smooth attenuation and the abilityto compensate for hot outputs and sensitive inputs.

We have done this for decades in direct boxes that connect speaker level signals to line level inoputs. In addition be prepared for some serious ground issues. They may or may not occur byut using an isolation transformer will serve you well. We also insert a 1mfd electrolytic capacitor in series with the hi side line out for DC blocking. We have built thousands of these devices over the years and never had an issue.
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post #13 of 14 Old 12-12-2012, 02:06 PM - Thread Starter
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Gizmologist & SAM64;

I sure appreciate your help today; I knew a little before, I know a lot more now, from this discussion, my Audio Source is a Speaker Signal, and I basicically need a Line Signal to go to the FM Transmitter; this Voltage Divider using the Resistors turns that Speaker Signal into a Usable Line Signal for the Transmitter.

Gizmologist:

Before I had a chance to read the last Post I had went to Radio Shack and decided to go the Resistor Route because of the simplicity and I had bought the 10K Resistors, they are cheap $1.20 for 5, I will get some 100K Resistors, do I still want 0.25Watt? do you agree with the following:



So to Clarify;

In my application, I would keep the dual leads/wires that I created coming from the Audio Source or what used to feed the enclosed Speaker. One set of leads or wires (Positive & Negative) would feed the remote Speaker through the Ear Phone Jack I have intalled; the other set of Wires(also, Positive & Negative) would feed through the Voltage Divider, attached first to the 'Speaker Out Side'; Positive to the SPEAKER OUT and Negative to the SPEAKER GND.

I would then run a wire from the 'LINE OUT' to the 'Ear Phone Jack Positve Terminal' and another wire from the LINE GND to the 'Ear Phone Jack Negative Terminal'; Plug in the FM Transmitter and both the Speaker and FM Transmitter should work!

Would this be correct? (except substitute R1 10K Resistor with a 100K resistor)

SAM64

I went the Resistor Only Route because if I need to adjust any Output to the Transmitter, the Transmitter has an Input Level Adjuster, if it doesn't work, I can always switch out the resitors for a Potentiometer later.

Again, Thanks for all the help. Doug.
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post #14 of 14 Old 12-12-2012, 08:28 PM
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The "line out" of your circuit -after subbing the 100k resistor- should go to the LINE IN on the transmitter.
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