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  1. audioguru2

    Transistor collector current

    A transistor needs to have a high collector current (and a high base current which reduces its input impedance) and a low resistance collector resistor when it is in class-A and it needs to drive a low resistance load.
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    The 2N3055 is an emitter-follower without voltage gain. Its dropout voltage might be only 2V. Because it has no voltage gain then the stability (possible oscillations) of opamp U2 is not affected. Using a PNP common-emitter transistor adds voltage gain which might cause U2 to oscillate. Our...
  3. audioguru2

    Adding led brake lights

    The transistors in your circuit are emitter-followers with a very low base current so the 1k resistors can be replaced with wires. They can be up to 33k ohms but each pin needs an additional resistor to ground as an attenuator so that the input voltage never goes higher than the supply voltage...
  4. audioguru2

    Adding led brake lights

    Again, you drew your LEDs upside-down. The cathode (the line) is supposed to connect to the resistor to ground. The anode is supposed to connect to the transistor. Your "VCC/2b" has its resistors backwards. Unused opamps should be properly disabled so they don't oscillate and cause problems...
  5. audioguru2

    Adding led brake lights

    An LM324 quad opamp has inputs that work as low as 0V and has plenty of output current to drive transistors. An LM358 is a dual opamp with the same opmps.
  6. audioguru2

    Adding led brake lights

    Your LEDs are upside-down. The 741 opamp's inputs do not work if they are less than about 3V and you have one input at only 1.25V. Here in Canada it is illegal to change lighting on vehicles because too many kids used extremely dim and narrow-angle LEDs that cannot be seen at night.
  7. audioguru2

    diy 2.1 pc speaker

    I use my excellent-sounding speakers to play music, not the sound effects from games.
  8. audioguru2

    diy 2.1 pc speaker

    All the reviews for it are different. One owner says, "Great value for money, but could be better" and "not good for music".
  9. audioguru2

    diy 2.1 pc speaker

    Was the 5.1 system made by Bose? Their sound systems are awful. Look in Google at "Bose Bashing" where people say how bad their stuff is. It is a very cheap radio sold at a very high price.
  10. audioguru2

    diy 2.1 pc speaker

    A 3" speaker is used in a cheap clock radio. It cannot survive more than a few Watts. Maybe your 3" speakers are better and can survive 6W? Where did you find "15.5VDC"? A 12V transformer when full-wave rectified and filtered makes 15.5VDC.
  11. audioguru2

    diy 2.1 pc speaker

    What is a "split power circuit"? Maybe a dual-polarity supply? A TDA2003 with a 15.5VDC single power supply produces 5.25W into a single 4 ohm speaker or 4.3W each into two 4 ohm speakers in parallel.
  12. audioguru2

    diy 2.1 pc speaker

    The TDA2030A by itself has an output power at clipping int a 4 ohm load with a 32V supply of only 18W and it gets very hot. The datasheet shows a TDA2030A driving two power transistors and has an output at clipping into a 4 ohm load with a 39V supply of 35W and the power transistors get very...
  13. audioguru2

    diy 2.1 pc speaker

    You need to know the impedance of the speakers. Then you can find out the voltage from the transformer. Speakers in series have low power and sound boomy because then the extremely low output impedance of the amplifier cannot damp their resonances. Then simply change the crossover frequency to...
  14. audioguru2

    diy 2.1 pc speaker

    I did not say that the power of the two ICs are not matched, I said the output DC offset voltages are not matched. Look at the datasheet: With a 14.4V supply, the quiescent output voltage is anywhere from 6.1V to 7.7V which is a range of 1.6V DC that when bridged will cause the voice coil of a...
  15. audioguru2

    diy 2.1 pc speaker

    The TDA2003 does not bridge well because the output offset voltage are not matched for the two amplifiers like a monolithic bridged amplifier IC. But you might be lucky so try it. With a 14.4V supply the bridged output at clipping into 4 ohms is 14 watts. If your speakers are 8 ohms then the...
  16. audioguru2

    0-30V Stabilized Power Supply

    1) Try shorting R10. 2) The driver transistor and/or output transistors might be leaking current, replace them. 3) C7 is an electrolytic type that has a voltage absorption problem. Use a film capacitor instead that is used in high quality speaker crossover networks. 4) Try adding a permanent...
  17. audioguru2

    need a project idea on noise sensing

    One of these electronics chat forums had your question but I can't remember which one and when. This site had a project that detects 3 different sound levels then lights an LED. You could build it with only one output to turn on your message machine and use a pot to set the sound level that...
  18. audioguru2

    0-30V Stabilized Power Supply

    The redwire circuit will not work with OPA445 opamps.
  19. audioguru2

    0-30V Stabilized Power Supply

    I can't remember which version you are making. my latest version works only with MC34071 or TLE2141 opamps and will not work with 741 or OPA445 opamps. Yes. There are many plastic films. Mylar is another one. Yes. I think your current meter is not calibrated correctly. Yes.
  20. audioguru2

    0-30V Stabilized Power Supply

    Then the input offset voltage of your U3 opamp is worse than the maximum spec'd. A TLE2141 opamp has a max input offset voltage of only 1.4mV and an MC34071 opamp has a max input offset voltage of only 5mV. Replace U3. Then maybe your U2 opamp also has its input offset voltage higher than the...
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