-They are genuine for RDS and looks. RDS has an inverse measuring relationship to IDSS.
-The bandwidth will narrow when the pot is at less than pass though max position. Worse reading should be when set at half its value. But it still is very wide.
Thanks Salas. Do you mind if i try to develop a digital input-switch and volume control via rotary enconder? I'm Curious if this would influence bandwith a lot.
My idea was to replace the alps potentiometer either with a r2r ladder or a digital potentiometer.
Whatever volume control style you prefer. Some even use optical attenuators, remote control, software code on controller chip and a display etc. Still if you will measure your bandwidth again for its narrowest point along the now conventional potentiometer's rotation you will see it remains very wide for audio use. There are better attenuator ways for functionality, precision, channels balance, subjectivity, than a resistive track mechanical pot. But they are a nice enhancement, not a necessity, because there isn't any general spec bottleneck problem they are called to solve in this case.
Is there an article that can explain input and output impedance? I know how to measure figure its Z. But how would you do it with an input--by the device's given specs?
The input impedance is approximately the value of the grounding resistor at the input.
But there is the impedance of the input semiconductor that is in parallel to that.
then there should be an RF attenuating resistor in series that may have an influnece.
And then there is the grounding resistor at the input to take DC blocking capacitor leakage to signal return. This is also parallel.
Take some typical numbers.
2M2 input grounding resistor.
1k0 RF attenuating resistor
100k input resistor
250k input impedance of a BJT stage.
250k||100k = 71k4
1k0+71k4 = 72k4
72k4||2M2 = 69k1
Call it 70k.
For 1.5Hz F-3dB passive roll off use a 1u5F DC blocking capacitor.
With jFET input semiconductor the 250k becomes enormous and leaves an input impedance ~97k
But there is the impedance of the input semiconductor that is in parallel to that.
then there should be an RF attenuating resistor in series that may have an influnece.
And then there is the grounding resistor at the input to take DC blocking capacitor leakage to signal return. This is also parallel.
Take some typical numbers.
2M2 input grounding resistor.
1k0 RF attenuating resistor
100k input resistor
250k input impedance of a BJT stage.
250k||100k = 71k4
1k0+71k4 = 72k4
72k4||2M2 = 69k1
Call it 70k.
For 1.5Hz F-3dB passive roll off use a 1u5F DC blocking capacitor.
With jFET input semiconductor the 250k becomes enormous and leaves an input impedance ~97k
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All BJT amplifier inputs have an input offset current. These currents MUST have a route to escape, else the output can be anywhere except zero volts.
Most Power Amplifiers have this required route formed with a grounding resistor. Typical values vary from 5k to 500k
Theoretically, jFET input power amplifiers do not have any input offset current and so should not need to provide any escape route, but you will find that most jFET input power amps do adopt a grounding resistor. Typical values are 47k to 500k.
If one fits a DC blocking capacitor at the input then an EXTRA grounding resistor should be fitted before that capacitor. These typically can be from 47k to 10M
BTW.
fitting a DC blocking capacitor to the input prevents a DMM resistance measurement of the input Z impedance. One needs to look at the schematic instead.
Most Power Amplifiers have this required route formed with a grounding resistor. Typical values vary from 5k to 500k
Theoretically, jFET input power amplifiers do not have any input offset current and so should not need to provide any escape route, but you will find that most jFET input power amps do adopt a grounding resistor. Typical values are 47k to 500k.
If one fits a DC blocking capacitor at the input then an EXTRA grounding resistor should be fitted before that capacitor. These typically can be from 47k to 10M
BTW.
fitting a DC blocking capacitor to the input prevents a DMM resistance measurement of the input Z impedance. One needs to look at the schematic instead.
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The resistor is also making sure that decent current travels through the IC cable.
If there is no resistor and you use a fet input, there is nearly no current in the signal and the slightest noise will make huge impact in the signal. Higher signal current will make it more resistant from noise.
If there is no resistor and you use a fet input, there is nearly no current in the signal and the slightest noise will make huge impact in the signal. Higher signal current will make it more resistant from noise.
As far as I know the level of signal current makes no difference to signal to noise ratio.
The ratio of signal to noise is the signal voltage level with reference to the noise level when no signal voltage is present.
The source impedance is the load that interference sees. The 100k grounding resistor is invisible to interference attacking the interconnect, when the interconnect is connected.
What interference does manage to attack the source impedance and generate an interference voltage across Zin should be filtered by the low pass filter BEFORE it gets to the input node.
If the interconnect is disconnected and one has NO SIGNAL voltage then the interference will see the Zin and interference noise voltage will be significantly higher. But in this situation you and I are not listening to music/audio.
The ratio of signal to noise is the signal voltage level with reference to the noise level when no signal voltage is present.
The source impedance is the load that interference sees. The 100k grounding resistor is invisible to interference attacking the interconnect, when the interconnect is connected.
What interference does manage to attack the source impedance and generate an interference voltage across Zin should be filtered by the low pass filter BEFORE it gets to the input node.
If the interconnect is disconnected and one has NO SIGNAL voltage then the interference will see the Zin and interference noise voltage will be significantly higher. But in this situation you and I are not listening to music/audio.
The AC voltage of the primary has nothing to do with the diodes. They are connected at the 15+15V secondary side. The MUR120 200V peak inverse voltage spec (VRRM) is super ample then. They are faster than their high VRRM sibling. They will be reliable for 200-300mA hot-rod choice even. Heat builds up fast in small components when the current is constant like here so at their 1A nominal they would be too hot that is why I derated them. You mount them little proud on the pcb for air to can go around them.