![]() #MIXING TWO STEREO MASTER PLUS#It’s also a revelation in terms of what an introductory digital console can deliver.īased on the same pioneering design approach as the industry-leading SD series, the S21 boasts the same proprietary audio algorithms plus a new ARM QuadCore RISC processor which runs in harmony with the FPGA core. Step up to the S21’s worksurface, complete with dual P-CAP multi-touch screens, 48 flexi-channels, the equivalent of 46 buses and benchmark 96kHz performance, and this console’s heritage is clear – the S21 is every inch a DiGiCo desk. How? Meet the S21 – a world-class DiGiCo mixing console at an astonishing price. This capacitor helps by reducing a potentiometer scratching noise a little bit.DiGiCo’s world-renowned innovation, deep feature-set and flagship audio quality of our high-end digital consoles is within reach of everyone. The potentiometer after the first stage regulates the volume of that channel. Mono is good enough for this application. Initially I want4ed to make a stereo version, but stereo version gets significantly more complicated(twice as much op amps), and especially with volume potentiometers, which need to be dual gang. if you want to have almost zero noise, you should use OPA4134 which is double the price but it has a bit less noise. The operational amplifiers on the schematic are OPA4316. That 100pF capacitor in parallel with the feedback resistor is there to limit the upper frequency limit, so the amplifier does not need to amplify very high frequency noise. ![]() The operational amplifier in the first stage is configured into a simple adder with a gain of 1, mixing both left and right channel into one. This removed and unwanted DC bias from being amplified. Then, the signal is decoupled with two polyester capacitors. It also eliminates the unwanted noise if nothing is plugged into input jack. #MIXING TWO STEREO MASTER DRIVER#By loading the input device you supposedly get a little bit better sound quality, but that really depends on the driver type in the device itself. ![]() Ideally You could put 33 ohms here to better simulate the headphone impedance, but I think it is not necessary. The input stage (two identical circuits for two channels) first loads the signal lines with 1k resistance. I also included a small LED to indicate the presence of 5V at secondary. With isolation, these problems are omitted. In the first revision I didn't have the isolation and ground loops were introduced connecting PCs and other devices together with audio cables and this way a lot of unwanted noise was introduced in the audio output. This way this box is isolated from the power supply. This converts the USB input 5V into an isolated 5V. Then the signal goes into an isolating DCDC converter. In reality, this ferrite bead could be omitted with probably no side effects. ![]() I put it there so no high frequency noise could be passed into the circuit. ![]() The ferrite bead does not allow high frequencies to pass through. I route the 5V from USB cable through a small ferrite bead. I decided to use micro USB connector, since everyone has a lot of micro USB cables laying around. I decided to power this circuit with 5V USB cable, since it does not consume much power, and USB chargers are everywhere. ![]()
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