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  1. Audioguru

    Digital music player with a Tivoli Audio Model One

    The Chinese amplifier has a Chinese IC and its datasheet is written in Chinese. The datasheet shows a graph of its high heating with a 5V supply and an 8 ohm speaker. It also shows high heating with a 3.3V supply and a 4 ohm speaker. The IC's mode can be switched to work in class-AB or in...
  2. Audioguru

    GY6 AC/DC Reg/Rect - Are Both DC and AC regulated or just AC?

    The cheap Chinese regulator has no spec's. Post a video of it smoking then blowing up.
  3. Audioguru

    Soldering queries

    A cheap soldering iron does not have a controlled temperature. To turn on fast and allow you to make many solder joints one after the other then its power is too high which causes it to get hotter and hotter if it is sitting doing nothing. Then the pads on a pcb lift, the tip wears out soon and...
  4. Audioguru

    2018 Science Olympiad Hovercraft Help Needed

    An ordinary little variable resistor can control the much higher current through a power darlington transistor. The extra power is not controlled with PWM, instead the extra power is converted to heat in the power darlington transistor.
  5. Audioguru

    Questions regarding H-bridge

    Do you understand that Q1 and Q3 will only barely turn on conducting a very low current? They are "followers" not switches. If you want them to switch on well then their gate must be 10V higher than the power supply voltage. Usually P-channel Mosfets are used on the high sides of an H-bridge.
  6. Audioguru

    12v DC photocell switch that powers one circuit at day and another at night?

    A 12V solar panel will power a 12VDC/65W load during the day if it is in direct sunlight. It powers nothing at night. You need a battery and a charger for it to power a load at night.
  7. Audioguru

    class b amplifier components

    Your amplifier is class-AB, not class-B. It is the output stage of an audio amplifier using emitter-followers that have no voltage gain, the gain is a little less than 1. You need a third and probably a fourth transistors to provide the voltage gain of a little more than 100 (40dB) that you...
  8. Audioguru

    Question about active low pass filtering

    Almost any opamp works fine at 7kHz except a lousy LM324 and LM358. I doubt if LTspice would consider a 50 years old 741 opamp that has trouble above 9kHz.
  9. Audioguru

    Capacitor charging itself?

    On another thread, this student found out that this same teacher made a mistake about capacitors. Then maybe this teacher has a screwed up idea about charging a capacitor?
  10. Audioguru

    Hobbyist Station

    50 years ago I tested a few Weller tip temperatures and chose 700 degrees F and have used it ever since. Why mis-adjust the temperature with a knob? The cheap soldering station regulates the temperature of the heater, not the tip. My Weller regulates the temperature of the tip.
  11. Audioguru

    Question about active low pass filtering

    The Bode plot of Vout/Vin has a peak at 4.3kHz and a slope of 12dB/octave. Why radians? The CAD plot has a peak at 7kHz and a slope of 12dB/octave. LTspice has a peak at 1.3kHz and a slope at 6dB/octave. Which one is correct??
  12. Audioguru

    Hobbyist Station

    For the low price, its "temperature setting" might be just a simple light dimmer circuit that adjusts its idling power so its tip has no temperature control and cools too much when you are soldering then heats back up slowly when you stop soldering. My Weller soldering station (is reliable and...
  13. Audioguru

    Design bass amplifier

    100 Euros is not much money for 2 fairly good speakers. Here is an American website with good inexpensive speakers and this is a pretty good 8"/60W woofer: https://www.parts-express.com/dayton-audio-dc200-8-8-classic-woofer--295-310
  14. Audioguru

    9 way clap switch

    The circuit with the old 7490 counter IC is missing a supply bypass capacitor and is missing diodes across the relay coils. The 7490 is shown with its positive supply pin 5 disconnected and its clock pin "powered" from the positive supply. The 7490 also has TWO pin 1's connected in different...
  15. Audioguru

    Question about active low pass filtering

    1) The negative DC feedback is obvious. 2) The gain for low frequencies is not affected by the 5n6 and 560p capacitors. 3) "Gain for rising" might be talking about Easter. The mid audio frequencies in this filter are shown to rise only 2dB in my simulation:
  16. Audioguru

    LED light: 120V and 25watts vs 12Volts and 25 watts: whats the difference?

    I am a very powerful guy because I have a lot of energy.
  17. Audioguru

    9 way clap switch

    I bet my dog can activate those relays. Even though my dog cannot clap!
  18. Audioguru

    Design bass amplifier

    Yes, there are many cheap poor quality and poor performing speakers around. They are Chinese and have no datasheet. But there are also many not too expensive excellent speakers around made in The West and each one has a detailed datasheet. A tiny little portable Bose bluetooth speaker was...
  19. Audioguru

    Two stage preamp designing

    The high impedance collector output of the first transistor is extremely overloaded by the very low emitter input impedance of the second transistor. The second transistor should not be a common base type. Your schematic will be easier to read if you turn off all the Chicken Pox dots.
  20. Audioguru

    Design bass amplifier

    The Radio Shack enclosed speaker had a really good 6.5" woofer probably designed for a ported enclosure but it was in a sealed enclosure producing bongo drum resonance sounds. The tweeter was very cheap and sounded awful. When people heard their awful sounds in the store then none were sold so...
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