I think I had in my head the 120R value from Rod Elliots page that was linked, he was using that value because of the 120R headphone compliance. Just use the more common 100 ohm resistor instead of the 120, you will get slightly more voltage, here is the math.
(R2/(R1+R2))*Vin=Vout
(10/(10+120))*12=.9v
(10/(10+100))*12=1.09v
(R2/(R1+R2))*Vin=Vout
(10/(10+120))*12=.9v
(10/(10+100))*12=1.09v
I have one mathematical question: from my calculations it seems that the 100 Ohm should dissipate 1.2W, so the 1/4w is too low in this case. Isn't it?
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Yes you are correct, sorry I see where you wrote 1/4watt in schematic.
You will want a 5 watt resistor for the 100R. A 1/2 watt will be good for the 10R because it will only dissipate 120mW.
IF the input impedance of the transmitter is high enough like the common 10k value of most gear you could substitute the 100 ohm resistor with a 1k resistor, and substitute the 10 ohm with a 100 ohm, so you are increasing them by a factor of 10. The Vout will be the same but now you can use 1/2 watt resistors. The initial lower values were because we were not sure what it was going to drive so you want the output Z as low as possible. Output to input you usually want a 10x for good transfer. So if input impedance of your headphone transmitter is 10k, an output impedance of 1k is fine.
You will want a 5 watt resistor for the 100R. A 1/2 watt will be good for the 10R because it will only dissipate 120mW.
IF the input impedance of the transmitter is high enough like the common 10k value of most gear you could substitute the 100 ohm resistor with a 1k resistor, and substitute the 10 ohm with a 100 ohm, so you are increasing them by a factor of 10. The Vout will be the same but now you can use 1/2 watt resistors. The initial lower values were because we were not sure what it was going to drive so you want the output Z as low as possible. Output to input you usually want a 10x for good transfer. So if input impedance of your headphone transmitter is 10k, an output impedance of 1k is fine.
How can I now the input impedance of my headphones receiver? On the site, it says: 24 Ohm. Is it the resistance we are looking for?
From their website you linked.
"Listen to your favorite music wirelessly, from over 300 feet away. This RF transmitter and rechargeable wireless headphone reproduces rich sound from almost any source and features auto on/off"
If they are advertising it can be used with almost any source I don't think the input impedance is 24, I am thinking that the drivers in them are 24 ohms. I can't find any information on the exact input impedance of the transfmitter, but like I said if they are advertising that any source can be used then it must be 10k or higher.
"Listen to your favorite music wirelessly, from over 300 feet away. This RF transmitter and rechargeable wireless headphone reproduces rich sound from almost any source and features auto on/off"
If they are advertising it can be used with almost any source I don't think the input impedance is 24, I am thinking that the drivers in them are 24 ohms. I can't find any information on the exact input impedance of the transfmitter, but like I said if they are advertising that any source can be used then it must be 10k or higher.
Using a signal generator and a 1kHz sine wave place a 1k resistor in series with the input of transmitter. Measure the voltage before and after the 1k resistor, lets call the voltage after resistor V2 and the voltage from the signal generator V1.
1000*((V2/(V1-V2))=Zinput
1000*((V2/(V1-V2))=Zinput
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