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This category was created to discuss various questions and topics regarding ExpertSDR3 operation.

TOPIC: Low output power/low Mic drive when using a Motu M4 with an AT2020 Mic

Low output power/low Mic drive when using a Motu M4 with an AT2020 Mic 03 Mar 2024 20:11 #1

Hi all, I'm really struggling to get enough output power (Around 40W) with my Motu M4 and Audio Technica AT2020 Mic.

I've tried various other audio interfaces such as a USB soundcard a Zoom H1N (In audio interface mode) and even generated a 1KHz tone using Audacity which will all give me 100W easily.

It seems with my Motu M4 it is very difficult to get it to 0dB mic output within EESDR3, to get to 0dB or very near I end up having to have the gain up that high on the Motu M4 I will get the red square lighting up showing I'm clipping. Or I have to put the Boost right up in the EESDR Software.

Does anyone else in this group have a Motu M4 or even a M4 with an AT2020 Mic?
Any help would be gratefully appreciated.
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Low output power/low Mic drive when using a Motu M4 with an AT2020 Mic 11 Mar 2024 10:27 #2

  • ON7WP
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first of all how do you measure power. I hope with a PEP meter. Normal meters should show only 25W and this is perfectly normal.

second not sure if you understand digital audio. If you have 16 bits available it is MADNESS to use the upper bits only. In order not to get any distortion at the DAC side at the receiver you should NEVER put more than -12 dBFS into the adc. If you go up to 0dBFS your DAC will never be able to recreate distortion free signals, even worse with processed audio.

So if you can see the ADC input (Thetis has this function, or else you can use external software like the Orban sound level meter free app, you should set your microphone for this level, so not 0 dB !!! In that case you are already 12 dB too high.

The Motu is a 24 bit device so why be an idiot and only use the two MSB if you have 22 unused ones ????

Stop thinking end of scale.
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