Hi all,
I'm trying to understand and learn some things dealing with musical instrument amps.
This started with a discussion about converting a headphone out of an old electric piano to a line out level. I found this schematic online, which raised some questions. (See first attachment.)
1. The 100 ohm resistor between signal and ground:
100 ohms is not that much resistance really. How does this not just basically short things out (the amp of the mp3 player in this case)?
Secondly, what does it do exactly? (As in, if you were designing a device to lower a headphone signal to a weaker line level, why would you include this?)
2. What's the effective difference between the parallel (signal to ground) and series (in the signal path resistor)?
I feel like I could explain how each of these lowers the strength of the signal that results from this circuit.
a. The parallel resistor "sinks" most, but not all of the signal to ground, so what's left is a weaker signal.
b. The series resistor turns some of the signal's energy into heat energy, so what's left is a bigger signal.
Are either of these right? Which is the correct approach (or in what cases is one approach the correct one, and in what cases is the other the correct one)?
I hope it's somewhat clear what I'm trying to understand, and I appreciate any help. To some extent, I realize I don't know enough to ask the right questions.
I also have some questions about the second attachment. This is the schematic to an amplifier of an electric piano.
I've circled two resistors in blue. Please let me know if I've understood the functions of these correctly (and what I've gotten wrong).
1. The one on the left is a resistor/capacitor combination. It filters out frequencies above a certain threshold. (Looking at an online calculator, it looks like it filters out frequencies above around 3,500 Hz. Is it correct to say that even though 12 ohms is not much resistance, it doesn't short the amp because only part of the signal (AC above 3500 Hz) is actually getting to ground?
2. The one on the right serves to lower the strength of the signal. It simply sends much of the signal to ground, and what's left over goes to the headphones.
Thanks so much!
I'm trying to understand and learn some things dealing with musical instrument amps.
This started with a discussion about converting a headphone out of an old electric piano to a line out level. I found this schematic online, which raised some questions. (See first attachment.)
1. The 100 ohm resistor between signal and ground:
100 ohms is not that much resistance really. How does this not just basically short things out (the amp of the mp3 player in this case)?
Secondly, what does it do exactly? (As in, if you were designing a device to lower a headphone signal to a weaker line level, why would you include this?)
2. What's the effective difference between the parallel (signal to ground) and series (in the signal path resistor)?
I feel like I could explain how each of these lowers the strength of the signal that results from this circuit.
a. The parallel resistor "sinks" most, but not all of the signal to ground, so what's left is a weaker signal.
b. The series resistor turns some of the signal's energy into heat energy, so what's left is a bigger signal.
Are either of these right? Which is the correct approach (or in what cases is one approach the correct one, and in what cases is the other the correct one)?
I hope it's somewhat clear what I'm trying to understand, and I appreciate any help. To some extent, I realize I don't know enough to ask the right questions.
I also have some questions about the second attachment. This is the schematic to an amplifier of an electric piano.
I've circled two resistors in blue. Please let me know if I've understood the functions of these correctly (and what I've gotten wrong).
1. The one on the left is a resistor/capacitor combination. It filters out frequencies above a certain threshold. (Looking at an online calculator, it looks like it filters out frequencies above around 3,500 Hz. Is it correct to say that even though 12 ohms is not much resistance, it doesn't short the amp because only part of the signal (AC above 3500 Hz) is actually getting to ground?
2. The one on the right serves to lower the strength of the signal. It simply sends much of the signal to ground, and what's left over goes to the headphones.
Thanks so much!
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