HR Noise 1: High Pitch Noise
Last Updated on May 21, 2020
It's on Raspberry Pi 3 with Raspbian, UCA222 (16-bit encoding), and my DIY preamp with LM386 connected to Les Paul SL, using speakers embedded in the display to monitor sound.
Cleaned up my desk, (removed external 330 yen stereo speakers, got distances among devices and so on).
-60dbV+ at the high pitch is redueced to less than -60dBV. The distances among devices seems to reduce the guy. Hmm.
No mystery guys.
Environment for HR
1. behringer's UCA222: It has Line In. Its 16-bit encoding needs to control input level better than 24-bit encoding. -12dB to -18dB level recording means 1/4 to 1/8 volume level comparing to the maximum. 16-bit quantifying means 65,536 quantities (-96db at minimum) to record sound, so 16384 to 8192 quantities are valid in -12dB to -18dB level recording which equals to -60dB to -66dB level recording in 24-bit encoding (16,777,216 quantities = -144dB at minimum). Its chip is "Texas Instruments PCM2902 Audio Codec" according to "lsusb" on Terminal of Raspbian (Raspberry Pi OS). "alsamixer" on Terminal of Raspbian only shows the PCM parameter for UCA222.
2. UGREEN's USB Mic Input and Stereo Output: It has Mic In which has no need to get high level signal. Caution that Mic In has DC bias, e.g., 5V and 2K ohms output impedance, etc.
1. Windows Laptop
2. Raspberry Pi 3 with Raspbian (Raspberry Pi OS)