I'm wondering if there is a simple way to measure an amp's input impedance. I have a multimeter and have used it to measure pickup resistances but I must admit I'm not exactly sure what I'm doing with it, I just followed instructions online.
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Double Bass Measuring an amp's input impedance?
- Thread starter Ethan Eriksen
- Start date
No really simple way because of the input capacitor.
You need a (voltage) frequency generator, an external resistor (500 KOhms to 1 MegOhms) and a multimeter (voltage measurement).
In most cases the frequency generator is missing.
You need a (voltage) frequency generator, an external resistor (500 KOhms to 1 MegOhms) and a multimeter (voltage measurement).
In most cases the frequency generator is missing.
Can't you just use a phone or computer? There are plenty of frequency generators in the app store.
Measuring input impedance and calculating output impedance calculation calculate audio amplifier op-amp how to measure impedance voltage gain total loudspeaker speaker microphone resistance resistor bridging matching test load loudspeaker source resistance - Why input impedance is in parallel and output impedance is in series? - sengpielaudio Sengpiel Berlin
Scroll down until you see "Input Impedance Measurement and Calculator."
Scroll down until you see "Input Impedance Measurement and Calculator."
While this reference is correct, you do not need a variable external resistor. Instead you can use a fixed resistor and measure the voltage at the output of the signal generator and after the external resistor.
From the voltage drop you can find out the resistance relation from external to internal resistance and from the known external resistance determine the internal one (the two resistances build a voltage divider).
It helps to have an external resistor in the same range as the internal one for a better measurement.
I didn’t think of computerized signal generators as in phones or computers.
A good hint to get a frequency generator for audio.
But I didn’t want to risk to blow the output of such a device by accident, so I would rather use a cheaper audio interface than the headphone out from an expensive phone/computer.
And don’t forget that there is also an output impedance from the device. It does not add to the external resistance for measurement, but the measurable output voltage at the generator might change a bit, depending on the total resistance, if you change the value of the external resistor.
My tact is to read the the PDF of the Users Manual for whatever I'm looking at purchasing and most of the time the input impedance is in the back of the "book" under "Specifications" for the inputs.
I've only found a very few manuals that don't include that measurement.
I've only found a very few manuals that don't include that measurement.
