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  1. Audioguru

    Class AB Power Amplifier Design

    Guess what? The old TDA2030 and the improved TDA2030A are already obsolete and Digikey has none. TI still make the LM1875 and LM3886 linear class-AB amplifiers. A Company Txxxx invented class-T digital amplifiers but the company went bankrupt and now clones are made in China.
  2. Audioguru

    Class AB Power Amplifier Design

    Mosfets need a much higher gate-source voltage (about 6V) than a bipolar transistor base-emitter (about 1V) so the power supply voltage must be about 10V higher for the Mosfets amplifier compared to the bipolar transistors amplifier for the same output power. A class-AB audio amplifier made...
  3. Audioguru

    Class AB Power Amplifier Design

    16W RMS into an 8 ohm speaker requires a signal that is 11.3V RMS and a current that is 1.42A RMS. A class-AB amplifier is about 55% efficient so when the output power is 16W then the wasted heating power is 13W so the total power from the power supply is 16W + 13W= 29W. 11.3V RMS is (11.3 x...
  4. Audioguru

    5 Transistors Linear Triangle Wave Generator

    Your 'scope photo does not show the amplitude and offset bias voltage.
  5. Audioguru

    Does the TDA2030 need negative potential?

    The datasheet for the old TDA2030A has specifications with a +/-16V supply so that it does not overheat. Only 10W into 8 ohms is guaranteed but 12W is typical with 0.5% distortion. The datasheet shows two bridged TDA2030A ICs typically producing 34W into 8 ohms at probably 0.5% distortion with a...
  6. Audioguru

    SuperCap Charging and Delivery System using Solar Panels

    A super cap is not a battery. A super cap discharging voltage drops steeply. A rechargeable battery keeps its voltage up until it is nearly dead.
  7. Audioguru

    10.7 MHz oscillator with transistor

    The very simple 10.7MHz oscillator you posted in post #15 has an output which is AM and FM combined so it is a poor way to test an FM demodulator that is supposed to reject AM.
  8. Audioguru

    Hook double horn to separate or single relay

    They are not "air" horns. Instead they are ordinary electromagnetic car horns.
  9. Audioguru

    How would a twisted pair effect a signal

    Before old computerized cars were made, most drivers did not bother replacing plugged air filters and therefore drove around running rich making black exhaust air pollution. Therefore maybe the computer was programmed to make the cars run lean to "fix" that problem. Maybe in those days they did...
  10. Audioguru

    How would a twisted pair effect a signal

    A twisted pair is used for telephone lines to cancel common-mode interference. The twisted pair is completely balanced with a signal on one wire and the inverted signal on the other wire without either wire grounded like it would be on a car. On a car a twisted pair would produce only a little...
  11. Audioguru

    How would a twisted pair effect a signal

    You gain only a little more maximum power by polluting the atmosphere by running rich. How often or do you ever drive at maximum power??
  12. Audioguru

    Please advise a good substitute potentiometer

    Electric brakes on an antique trailer? Usually the truck that pulls the trailer has the hydraulic brakes. Of course the old rheostat is obsolete.
  13. Audioguru

    Is it safe to switch between NiMH and alkaline batteries?

    Name Brand Ni-MH batteries made in the last 5 years have Eneloop chemistry that holds a charge for one year. Older or cheap Chinese batteries are too old to hold a charge. Name Brand alkaline batteries hold a charge for 10 years.
  14. Audioguru

    How to: power this old ringer?

    Sorry, before I was wrong. The two mechanical gongs on an old Bell telephone were 1280Hz and 1610Hz. The ringtone heard on the caller's phone was 440Hz and 480Hz. The single ringer gong will sound like a door bell, the alternating 1280Hz and 1610Hz musical chord produced by the two gongs in an...
  15. Audioguru

    HELP with Schematics for magnet launcher

    The noob thinks the random parts he bought will not explode or set his house on fire!
  16. Audioguru

    Phototransistor

    Since you do not feed base current into a photo-transistor then the "gain ratio" does not mean anything. Instead, you look on its datasheet for its minimum brightness to output current ratio.
  17. Audioguru

    How to: power this old ringer?

    The old ringers needed to work miles away from a telephone switching center using very thin wires, and there might be two or three phones in a house in parallel, so their ringing currents needed to be very low. So they were designed to resonate mechanically at 20Hz then a very low current would...
  18. Audioguru

    Mosfet not Switching the current to load

    You are asking about your Mosfet and 555 timer but did not say what is their very important part numbers. 1) Most Mosfets need a gate-source voltage of 10V to fully turn on. Logic level Mosfets need 4.5V to fully turn on. The part number on the datasheet says what it is. 2) An ordinary old...
  19. Audioguru

    How to: power this old ringer?

    In Canada and United States an old phone ringer worked on 90V at 20Hz. It probably would not work at the 60Hz of electricity. An original Bell Telephone used two gongs. Each gong was hit 20 times each second and played different frequencies (440Hz and 480Hz). Your ringer has only one gong so it...
  20. Audioguru

    DC Motor Speed

    If the motor vibrates slightly because it is out-of-balance then it will produce a hum sound. If it spins at 6000RPM then the hum will have a frequency of 100Hz. Use a microphone that feeds an audio amplifier and measure the frequency with your multimeter.
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