![]() ![]() ![]() On a scope set to 20MHz BW the intro silence looks like noise of about 10% FS! Unfortunately the LS-10 uses some sort of ghastly Class D amplifier on the output, so al I can say is the noise performance is notably better than shown – in Audition the noise floor rises by 10dB when the LS10 is playing the silent intro compared to when the LS10 is not playing anything but terminating the input. So I had to record the Rightmark test signal onto a Olympus LS-10 and play the signal in from this, battery-powered, into the Logitech to get any decent results. The microphone input is terribly sensitive to earth loops, which is fair enough, Logitech never expected their device to be used like this. ![]() ![]() I used the freeware version of RightMark Audio Analyser. Then test the sound card as recommended by ALSA – one gotcha I suffered was that the noise cancelling microphone worked effectively and I thought I had a problem when hollering at the mic from a distance was thin and low volume □ It also picked up interference from the wi-fi. Then I have to stop the Pi jumping on the USB sound card USB Headsetīus 001 Device 009: ID 413c:1002 Dell Computer Corp. First I checked it appeared in the usb stack with lsusb ~ $ lsusbīus 001 Device 002: ID 0424:9512 Standard Microsystems Corp.īus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubīus 001 Device 010: ID 413c:2002 Dell Computer Corp. Getting it to work on linux was more complicated than plugging it in. I then extracted the original microphone capsule from the headset and soldered it to a phono socket just to test this out in the original circuit conditions. So I unsoldered the existing cable and threw it out, and soldered a stereo jack plug for the headphones and a phono line socket for the microphone. The bad thing about it is it’s the devil’s own job to solder, because as you heat the strand the synthetic coating melts, robbing you of heat and re-insulating the enamel you’ve burned off. The good thing about this is your headphone cable breaks later than if you used normal multi-strand audio cable, given all the flexing it has to take. Headphone cable uses fine strands of individually enamel insulated wires wrapped around a synthetic fibre core. Logitech A-0365A USB headphones control board Initially I wondered if the black stuff was a blown capacitor, but it was on both sides of the board so I figured it was probably glue from the connector, which was confirmed when I unsoldered the connectors, it came off like a gluey film. Nothing is designed to be repairable here, so the plastic USB module case was pinged apart with a flat-bladed screwdriver. It’s all part of experimenting to make a low-cost audio field recorder that can start by itself. Stereo output but mono on record, of course, but still useful. The USB part seemed to work, but headphones live on borrowed time, connectors and wiring tend to go, and everything is sealed, So I wondered if I could reuse the circuit board as a Pi soundcard. The Raspberry Pi has no audio input, and I had a pair of Logitech USB headphones that had gone faulty – the earth on the headset was a dis. ![]()
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