r/CircuitBending • u/Important_Guitar_528 • 1d ago
HELP!
hello, im new to all of this. Im trying to add a jack socket to this toy telephone, i cant get it to work tho... all the tutorials i have watched use a jack socket with only 2 prongs, but as you can see on the pictures, they have an extra. The yellow wires are the ones originally attached to the speakers. im losing my mind at the moment, hope someone can help thanks! :)))
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u/SUxEvil 1d ago edited 1d ago
If you leave the speaker in place, do you hear the audio in your audio out?
If I remember correct you need a resistor in parallel one that is 100ohm? Something like that.
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u/Important_Guitar_528 1d ago
not sure i understand, sorry
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u/SUxEvil 1d ago
The speaker closes a circuit, so if you add a line out with the speaker in place it should work.
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u/Important_Guitar_528 1d ago
sorry, can u explain in terms a 5 year old understands, im currently taking babysteps :O
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u/SUxEvil 1d ago
In some toys, when you remove the speaker, the toy checks if a speaker is connected. With no speaker, the toy thinks nothing is there and produces no sound. With a speaker connected, the toy turns on and says "OK, sound." When you remove the speaker, there is a trick you can use with a resistor: if you connect a resistor of 100 to, say, 450 ohms across the wires, the toy detects the resistance and thinks the speaker is still there, so it turns on. Essentially, the resistor acts as a fake speaker just to wake up the toy.
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u/BobKickflip 1d ago
This but use an 8ohm resistor, that's the dummy load that matches the speakers in most toys. I actually use 8.2ohm as that's all I can find but it's definitely close enough
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u/SUxEvil 1d ago
I remember something like..the 8 ohm resistor will waste power?
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u/BobKickflip 1d ago edited 1d ago
I've never heard that, and the devices that need it work fine. I guess if anything at all it'll waste as much as the speaker does, but if you can find the info that'd make it clearer.
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u/Important_Guitar_528 1d ago
THANKS I UNDERSTAND!!!! <3333
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u/maybeinthewoods 1d ago
They are correct, you can use a resistor to "trick" the toy into thinking there is a speaker soldered to the board.
But in terms of the jack that you're adding... Is that to connect an external speaker? Or to connect the toy to an external amplifier?
There are a few different types of audio signals, and they all vary in voltage. You have line-level, speaker-level, mic-level, instrument level.
Mic-level is the lowest voltage of the three and is used for transferring microphone signals.
Instrument-level is just above mic-level in terms of voltage.
Line-level is the industry standard for music/audio, before final amplification, and is what you'd see in 1/8" Aux and RCA cables - it is usually 2V or less.
Speaker-level is the highest voltage, and is what is actually connected to the speakers themselves. These can range from mW to hundreds of watts, like in the cases of large sound systems. The wires in your toy that connect to the speaker are speaker-level and are likely connected to a tiny amplifier within the circuit board.
Depending on what you plan on using that jack for, you'll want to make sure you stick within the voltages that are safe for whatever device you plan on connecting this toy telephone to.
In other words, if you're using the speaker-level output from the toy and sending it into another electronic device, you don't want the toy's output voltage to damage whatever device you're connecting this to. It would just be a bummer to connect this to something like a computer sound card's line-in port and end up frying the sound card's line-in circuitry, or whatever. Same goes for any amplifier or sound-system that you might try and connect this to.
I have a feeling that the circuit on this toy is all in one single chip, so you probably won't have separate pre-amp and amp stages that you could isolate and wire and tweak how you want.
That's probably TMI, but by soldering in a resistor in place of the speaker, you'd effectively trick the circuit into thinking there is a speaker connected, and you'd also be completing the circuit.
I tend to use my multimeter to measure my outputs on my circuits, so that I know where my final, speaker-level signal is being output from the circuit board (it's generally wired directly to the speaker drivers themselves). If you want to trace the line-level output, it may or may not be possible on a single-chip circuit like the one you have - because usually, amplifiers have a pre-amp (line-level) circuit, separate from the final amplification stages.
Hope that helps a little bit.
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u/NOYSTOISE 23h ago
If you disconnect the speaker, the transistor that boosts the signal for the speaker will not work. You could add a load resistor as suggested, but then your signal would probably have a pretty nasty DC offset. A better way might be to tap the signal at the base(pin) of the transistor, and see if you cant get a decent audio signal from there. It is best to add a capacitor to block DC to you output(1-10uF), and maybe a 1k resistor for good measure.
Circuits like this ones' speaker wires are usually connected to the amplifier transistor(S8050), and the hot side of the power supply, so if you simply connect the wires to the jack, your ground is actually positive. That's not really a problem unless your toy is sharing power with other things that are ground-negative. Personally, I think it's best to use ground-negative on the output jack, and don't fuss with the transistor amplifier at all. Sorry I can't post a photo to illustrate better. DM me if you'd like more info
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u/Mustardplugmint 18h ago
use a 3/8” jack for tight spots junior.
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u/Revised_Devices 𝙉𝙞𝙣𝙟𝙖 7h ago
Idk, there's something striking about a 1/4 on a small device, I've done it on pt-1s and 10s and it's 👌
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u/MetropolisJones 1d ago
I just bent that exact toy!
Your issue is that you bought a TRS (tip, ring, sleeve) jack instead of a TS (tip sleeve) jack. This is not a problem at all, just solder to the tip and the sleeve and it will work perfectly.