ThatMicPre - an open-source mic preamp

[antoine_glls]

Ah for some reason I hadn't thought of that. I found a 24V supply at a local electronics store and the preamp is working very well. Thank you for the design!

 

[zraxix]

Hi, and thanks for the great open design! I just put together my first ThatMicPre. However, the output is low and distorted even at the max gain. I've included some pics! Would appreciate it if anyone notices anything obviously out of place or can suggest troubleshooting advise! I'm running it into a Scarlett interface on using the line in port on the back, and powering off a bench top power supply.

 

[zraxix]

I would like to amend my previous statement. The distortion was due to a bad cable. The output however still seems very low

 

[georgenikolaou]

Hello guys,

thank you for this great project.
Please, I have a problem with the Matlab file.
I'm trying to use it but it gives me error.
Please could you inform me how to use it? What values and where I must put to give me results?

The version of Matlab that I'm using is R2023a

Thank you in advance.

 

[ojg]

Hi, and thanks for the great open design! I just put together my first ThatMicPre. However, the output is low and distorted even at the max gain. I've included some pics! Would appreciate it if anyone notices anything obviously out of place or can suggest troubleshooting advise! I'm running it into a Scarlett interface on using the line in port on the back, and powering off a bench top power supply.

Hi zraxix,

My first question is, what DC voltage are you suing ac power supply? 48V or at least 24V, I hope?

If that is correct then I would take out a multi-meter and measure the DC voltages at the V48P, V35P and V18P nodes.

 

[ojg]

Hello guys,

thank you for this great project.
Please, I have a problem with the Matlab file.
I'm trying to use it but it gives me error.
Please could you inform me how to use it? What values and where I must put to give me results?

The version of Matlab that I'm using is R2023a

Thank you in advance.

Hi georgenikolaou

Hard to help you without any more info. What is the exact error that you are getting?

How much prior experience do you have with Matlab or Octave? The file is a normal matlab function, the help text for the parameters show if you type "help micpre_gain2res"

 

[georgenikolaou]

Hello ojg,

Thank you for your reply.
Please attached you will find the error that it shows to me.
To be honest, I don't have an experience with Matlab.
Can you imagine which is the problem and what to change to have the results?

Thank you very much in advance.

 

[ojg]

You have misunderstood how you pass parameters to a Matlab function. You need to learn the basics of using Matlab first. There are many good Youtube videos on the subject.

 

[georgenikolaou]

Thank you Ojg, I will search it.

 

[georgenikolaou]

Hello,
Please, what's the input inpedance of your design? 2.4kΩ? I would like to use it with a dynamic Mic which has 320 ohm output impedance.
Is it suitable?

 

[ojg]

From the Github readme:

• Input impedance: 2.0kohm differential (1kHz)

 

[georgenikolaou]

Thank you Ojg.
Please which resistors change the input impedance?