I want to build a pre amp for a Panasonic WM-61A. I currently use a 9v battery and a simple resistor and capacitor to give it 'phantom power' in which to feed into my macBook Pro line-in, but there isn't enough gain.
I was thinking of powering some kind of circuit from the USB port so I was looking around for circuits to do the job.
Any thoughts on the circuit on this page, third picture down:
Davide Gironi: AVR Atmega audio input root mean square (RMS)
I would like to make a something a bit like the 'USB Art Dual Pre', obviously not with a built in USB sound card, it would be powered from the USB socket (5v) and would have an input and output that would connect to the line-in and the output of the macBook.
It would have a pre-amp like the picture I linked for the mic and also another channel so I could carry out 'loop back' calibration of the software and it would also enable me to carry out speaker impedance testing using FuzzMeasure.
The circuit seems like it would work, but I thought I would replace the 100K feedback resistor with a pot, so I could adjust the gain. Should I use a capacitor on the output to make sure if something fails in the circuit, I don't put DC into the 'line-in' of my mac?
Any thoughts on this idea? Could the opamp used be better?
I was thinking of powering some kind of circuit from the USB port so I was looking around for circuits to do the job.
Any thoughts on the circuit on this page, third picture down:
Davide Gironi: AVR Atmega audio input root mean square (RMS)
I would like to make a something a bit like the 'USB Art Dual Pre', obviously not with a built in USB sound card, it would be powered from the USB socket (5v) and would have an input and output that would connect to the line-in and the output of the macBook.
It would have a pre-amp like the picture I linked for the mic and also another channel so I could carry out 'loop back' calibration of the software and it would also enable me to carry out speaker impedance testing using FuzzMeasure.
The circuit seems like it would work, but I thought I would replace the 100K feedback resistor with a pot, so I could adjust the gain. Should I use a capacitor on the output to make sure if something fails in the circuit, I don't put DC into the 'line-in' of my mac?
Any thoughts on this idea? Could the opamp used be better?
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I've made 4 similar to this for some dynamic microphones. Try lower values for the 470K resistor.
Gianluca
Gianluca
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That's a much simpler way of doing it.
So I could take a wire from the top of the 180 resistor and feed it through a 0.1uF cap to remove the dc from the output, I could feed it directly into my macBook. And I could also feed the output from the cap through a 10K pot to ground and use the wiper pin to feed to my macBook, giving me a gain control. Correct?
So I could take a wire from the top of the 180 resistor and feed it through a 0.1uF cap to remove the dc from the output, I could feed it directly into my macBook. And I could also feed the output from the cap through a 10K pot to ground and use the wiper pin to feed to my macBook, giving me a gain control. Correct?
This is a similar circuit, how is the gain calculated?
Simple Electret Mic Preamp | The Electronics Zone
Simple Electret Mic Preamp | The Electronics Zone
You only have to connect the Mic to the base and the collector to the Mac, without any capacitor. The phantom coming from the Mac powers the capsule and the transistor. You have to adjust the 470K for maximum level before clipping.
Gain is given by the ratio RMacIn/180 Ohm. It should be a little over 10dB.
Gain is given by the ratio RMacIn/180 Ohm. It should be a little over 10dB.
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Now I understand! You need 40dB gain. The circuit in your link has only 20dB. Use R9=1kOhm for 40dB.
Now I understand! You need 40dB gain. The circuit in your link has only 20dB. Use R9=1kOhm for 40dB.
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So 1k for R1 and a 5v supply should be what I'm after then.
If I were to use a 1k resistor in series with a 10k pot, would this act as variable gain?
If I were to use a 1k resistor in series with a 10k pot, would this act as variable gain?
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