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3

"tick" sounds are usually created by something close to an impulse, or with a significant portion of impulsive energy. And time domain impulses create broad or wide-spectrum noise in the (FFT) frequency domain. So you are unlikely to be able to find or remove the majority of this noise with a generic (LTI) filter, such as an EQ or a notch. If the sound ...


3

Input filtering is a must. In addition to that I find it a must to use at least a full GND plane when dealing with switching regulators. Along with a full GND plane you can have much better routing for the other power connections. Some additional things to go along with that: Use every effort to keep all of the VSW connections as clustered together and as ...


2

The 3.3V regulator(1) (NCP1117 as commented) is missing its output capacitor. For the output capacitor of the NCP1117 applies: Frequency compensation for the regulator is provided by capacitor Cout and its use is mandatory to ensure output stability. A minimum capacitance value of 4.7μF with an equivalent series resistance (ESR) that is within the ...


2

I marked the harmonics of the fundamental 50Hz in red color. As you see the highest harmonics are at 150Hz, 350Hz, 550Hz, 750Hz. These are the 3rd, 7th, 11th and 15th harmonics. Is that order of significant harmonics something common in the world or completely random? They are common and are generated from transformers and other components Complex ...


2

Step 1: Scrap your existing design. Step 2: Read the TI data sheet for the TL494. Especially read through the "Layout" section near the end. There is a PCB layout example in that section though it is only a partial design. Here is TI's page with the full datasheet and application notes: http://www.ti.com/product/TL494 Step 3: Start a new schematic. Draw ...


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You are correct about the equation's restrictions. The words you are looking for are correlated and uncorrelated noise. That equation is for valid uncorrelated noise sources only. But it's a tall order to have all the noise sources in a circuit to be of the correlated variety, let alone be correlated in such that they match so perfectly and in exactly the ...


2

Input is signal frequency is 100Hz. I want to use the 6.5nV/sqrt(Hz) but it seems to be a spectral density, and I can't add it to a voltage This is where the bandwidth of the analog system comes in, the max bandwidth determines the noise. Let's say it's an ADC with a low pass filter at 1000Hz. The ADC would see: (1000Hz)^(1/2)*6.5nV/sqrt(Hz) = 2.05uV-rms ...


1

In any non-josephson-junction ADC, you will have analog comparators; their bandwidth likely will set the noise floor. How to estimate the noise of the Comparator? simply use the input FET gate capacitance. Using sqrt(K * T /C), the math behind switched-cap-sampling-noise, you'll find a 10pF capacitor produces 20 microVolts RMS noise. And a (more likely to ...


1

There are some serious issues in your circuit that cause it to act erratically. First of all, HCT chips are not meant to be run at 3.3V. Just look at any HCT chip datasheet. They need a supply between 4.5V and 5.5V to run properly. Most likely you do not want to use HCT but maybe HC chips that can work at 3.3V, but it will also have problems. Second ...


1

In an SMPS on the DC power supply side, Common Mode (CM) noise occurs when current exits the circuit and returns through the ground. Typically a DC supply is not grounded in two places (although it could be) as shown in the circuit above, this creates a ground loop and causes problems. Typically noise exits a device through capacitance and then returns ...


1

I'd go with: Use cascaded DC-DC (12->6) and precision LDO (6->5). In this architecture device will have additional noise from the DC-DC converter, and I am not sure if it is better than just using +5 V from the system. Sure, a switch-mode power supply adds a new source of noise – but that's a source that you can control! Typically, what you'd try is to ...


1

The regulator needs a bypass capacitor to be stable. The Teensy needs one too. The farther a capacitor is, the less effective it is. If there is 1cm between regulator and Teensy, you may only need one. If they are 1 meter apart, you definitely need two. Since they are on same PCB just draw both and you can choose later to leave one out.


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No problem going to 2f is = 50 Mbps. The probability of error depends solely on the Voltage becoming the wrong polarity when the discriminator has computed the polarity for that bit.. What affects the SNR? , that determines the BER. The slew rate indicates a variable amplitude and thus a variable SNR declining signal level, this also means a declining ...


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This is a MIDI controller, so I guess no analog audio processing will take place inside, which means the internal circuits should be rather noise tolerant. You should of course take care not to radiate noise which could affect other devices. Using PWM for your LEDs means traces carrying pulsed currents. I assume your LEDs, buttons and pots will be on a PCB, ...


1

As mentioned in other comments/answers, the definition of the needed S/N-ratio is missing. Some users - like broadcast studios in Europe - demand 114dB or more. It is not only about the possible Audio coupling, but any HF-interference is also critical. F.e., many users have problems to listen to weak radio stations at home when a nearby LED lamp (without ...


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