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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi BRN, Welcome to our forum. ;D Did you make the original version of this project? Did you substitute any parts? We need you to make some voltage measurements to determine the cause of the problem. Without a load on the output, connect the negative lead of a voltmeter to the negative end of...
  2. audioguru2

    Ultrasonic wave generator

    Hi Electro Seal, Welcome to our forum. ;D An ultrasonic transducer produces ultrasonic waves when fed an ultrasonic frequency within its bandpass from an oscillator. Digikey stocks many transducers. People witrh very sensitive hearing cannot hear an ultrasonic tone so why do you think the tone...
  3. audioguru2

    need to get rid of oscillating voltage...

    Hi Thieaux, In your other post I attached a transistor inverter with a voltage divider on its base that should trigger with an input voltage exceeding 3.2V but you said it didn't fix your problem. So I explained that changing its 100 ohm resistor to 39 ohms would make it trigger with an input...
  4. audioguru2

    How to smooth the audio switching pop or spikes?

    I played with surround sound about 30 years ago like you are doing now. I made a surround sound decoder system using Motorola's SQ Full-Logic ICs. Some vinyl records were made encoded especially for it. It also worked very well on ordinary stereo music and had knobs for the amount of effect and...
  5. audioguru2

    How to smooth the audio switching pop or spikes?

    The only thing your diode will do is become forward biased when the signal is loud and goes positive then it will charge the small capacitance at pin 3. Then pin 3's DC voltage rises and the opamp's output DC voltage also rises. It causes an odd action but I don't think it affects the sound. If...
  6. audioguru2

    How to smooth the audio switching pop or spikes?

    It sounds good now. ;D I don't know where you put the diode. It might rectify the sound if it gets louder than about 0.6V peak. With lower levels then it might mess up L-R.
  7. audioguru2

    How to smooth the audio switching pop or spikes?

    The echo is normal "ambience" in a surround sound system when the source is in stereo. It is caused by echoes in the recording studio or theater which have random phase, various levels and are delayed because they travel far. Poor quality electronic reverberation circuits make strange noises in...
  8. audioguru2

    How to smooth the audio switching pop or spikes?

    I don't know where the echo comes from. It takes a lot of hardware to make a delay then mix it to make an echo. I don't know what takes a noticeable time to charge. R12 and R13 have a source resistance of 5k. They can charge a 470uF capacitor to 63% of full charge in 2.35 seconds. It that a...
  9. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    I thought about using a 78L05 to replace the zener diode and the opamp, then also power the digital pots from it. You could add a trimpot in the gain-determining parts for calibration. Maybe there are enough steps and the resolution is good enough for you. You won't be able to smoothly sweep the...
  10. audioguru2

    How to smooth the audio switching pop or spikes?

    Hi Wellington, The impedance of the capacitor to ground at the voltage divider's "+6V" point determines how much crosstalk there will be. The impedance of the 100uF capacitor at 100Hz is only 16 ohms so the level of crosstalk from the 91k plus 100k resistors biasing the opamp is only 0.000084...
  11. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Roomi, This project has a voltage reference at the voltage adjust pot of 11.2VDC. Then the output amplifier boosts it up to 30V with its gain determined by the ratio of R12 and R11. Reduce the 11.2V reference voltage down to 5V with a voltage divider, adjust it with a digital pot then...
  12. audioguru2

    How to smooth the audio switching pop or spikes?

    Hi Wellington, Here are 3 causes of your pops: 1) Your CD4053 multiplexers have 3 different bias voltage dividers. With 5% 10k resistors their "6V" DC voltage could differ by up to 0.6VDC. Use only a single voltage divider. Test it by shorting together all 3. 2) You are switching when the...
  13. audioguru2

    How to smooth the audio switching pop or spikes?

    Hi Wellington, I have made many audio switching units with the CD405x multiplexer IC without pops. The trick is to DC bias the inputs, outputs and sources at the same DC level. Please attach the schematic of your switching circuit to see.
  14. audioguru2

    piezo buzzer using 555 ?

    Hi Thieaux, Since your locks must lock and unlock by swapping the voltage at their ends, I assume that they are not connected to anything when they are not operating. I also assume that the fluctuating voltage you measure is just interference from other electrical motors that is picked up by the...
  15. audioguru2

    piezo buzzer using 555 ?

    Hi Thieaux, Good it works, but it can be made more stable. Reduce the value of the resistors like this:
  16. audioguru2

    DC digital ammeter

    Hi Francois, The pcb for your meter kit already has a space for a current shunt resistor. But the space is for only a 5W resistor and you need it to dissipate 3.6W or 36W to measure 60A. You also need very heavy wires connected to the resistor. 2V/200A= a shunt resistance of only 0.01 ohms...
  17. audioguru2

    piezo buzzer using 555 ?

    Depending on how your door locks are wired, this inverter might work:
  18. audioguru2

    3rd Order Intercept Point

    Google has many links to a definition of the 3rd Order Intercept Point. It basically is the output level where the intermodulation distortion becomes very noticeable and keeps increasing with increased output level. Your circuit's gain is 30dB so the OIP3 output level is 19.586dBm, not the...
  19. audioguru2

    Wireless (Radio) Headphones

  20. audioguru2

    Pi Filter

    Hi Polis, I think a pi filter has two capacitors and an inductor between them. Your circuit is an LC lowpass filter. I searched Google for LC Power Supply Filter and got many links. This one shows that the LC filter must have the proper load or it will be resonant:
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