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  1. audioguru2

    + & - DC supply!

    Hi Guys, IC manufacturers have stereo (dual amps) headphones amp ICs with a built-in charge pump that developes a negative voltage for higher output, the elimination of a large output capacitor and the ability to operate from just 1 or 2 battery cells. Philips and others have a stereo car radio...
  2. audioguru2

    DC Motor Speed Modulation

    No Kevin, Sorry, you don't understand PWM. The motor's speed doesn't change with each pulse. The motor and its load have inertia, which needs a high torque to overcome. The inertia also causes the motor and its load to take time to change speed. The pulses occur much quicker than the delay...
  3. audioguru2

    Interpreting Datasheets

    Hi Shekhar, Thanks. Merry Christmas to you too! If you insist on cap-bypassing the emitter resistor of your transistor for a high gain, circuits using it will have variations in gain and frequency response due to the wide range of each individual transistor's h-parameters and also will have...
  4. audioguru2

    3V LED Chaser project

    Hi Ante, My original 3V LED Chaser project works fine. I made a number of changes so it could use 3.2V to 3.5V ultra-bright green, blue or white LEDs, and a 6V battery. The changes are numerous so I'll post it as a new project. I modified a 3V circuit with all the changes for the 6V circuit...
  5. audioguru2

    3V LED Chaser project

    Hi Guys, Correction: A 4584 IC isn't the same as a 74C14, and neither are the same for an oscillator's timing as a 74HC14 that is used in the 3V LED Chaser project. Since the 74HC14 drew too much supply current for the oscillators with a 6V supply, I wanted to use an ordinary Cmos hex Schmitt...
  6. audioguru2

    Buried wire detector

    Hi Kiwi, Welcome to our forum. My cable-TV guy had a very expensive and high-tech buried cable detector that showed the cable length and depth. I called him when my neighbour got a new driveway and my cable got broken. He dug up my whole yard finding telephone cables and old car parts. Pet...
  7. audioguru2

    Transistor as a switch

    Hi Kevin, It might be complicated to reverse the junction. Didn't you know that a transistor will be cutoff if you simply stop its base current? You could do it by shorting its base to its emitter with something like another transistor, or if its emitter is grounded, drive its base feed also to...
  8. audioguru2

    + & - DC supply!

    Hi again, You show a simple voltage divider that gives a "virtual ground" like all single-supply opamp circuits use. I thought you were building a "power" amp for your radio, that would need a conplicated high-power supply like this one from the same site...
  9. audioguru2

    The simplest audio amplifier

    Hi Kevin, Now the transistors don't have any regulation of their idle current so when they heat-up, or when the supply voltage goes up above 12V (when the alternator charges the battery to 13.8V) then again the transistors will fight each other and draw a massive current into each other, causing...
  10. audioguru2

    + & - DC supply!

    Hi, If you just want to make a negative 12V supply to be used with the 12V positive supply, a bridged amp (two amps, driven out-of-phase, and a speaker connected between them) effectively doubles the voltage for up to 4 times the output power than a 12V amp. Most car radios today use that...
  11. audioguru2

    The simplest audio amplifier

    Hi Kevin, I didn't see your last amp until now 'cause it took too long to load. What are you doing? You can't use inverted and non-inverting drive to a complimentary pair, they just fight each other modulating the supply current and blow the fuse without swinging the output up and down. You...
  12. audioguru2

    The simplest audio amplifier

    Hi Kevin, You need more than just push-pull. Todays ordinary car radios use a cheap and simple bridged-amps IC that puts out 21V p-p (with a 12V supply) into each 4 ohm speaker, without using a negative supply nor output coupling capacitor. But the crappy 20 ohm flimsy speakers with tiny magnets...
  13. audioguru2

    The simplest audio amplifier

    Sorry Kevin, Many factory car radios have 4 bridged amps that (with a 12V supply) can deliver 14WRMS per amp at low distortion into 4 ohm speakers. Most have 4 amps for a total of 56W. They operate cooly and fairly efficiently. How much power do you expect your "2 PNP transistor attenuator...
  14. audioguru2

    "Power?" Inverter

    Hi Ante, Without a load in this circuit, or if the transistors had enough gain and drive, the capacitors will have a brief reversal of polarity of only about 0.6V, with a collector at 0.1V and a base at 0.7V. Electrolytics can handle that with no problem.
  15. audioguru2

    Site's Clock

    Hi Yevgeni, I have entered my current time twice. Once when the server was in Greece and again when the server was moved to California. The site's hour is correct but the minutes are about 19 minutes fast. Look at the site's clock near the top of this page, isn't your clock wrong too?
  16. audioguru2

    3V LED Chaser project

    Hi Guys, It works perfectly! My "6V" green ultra-bright LED Chaser is brighter than before and draws only 250uA from the battery between flashes and with the brightness turned down. I replaced the 74HC14 hex Schmitt inverters IC that draws too much current at 4V to 6V with a 4584 (same as a...
  17. audioguru2

    SAW filters

    Hi Andrew, A crystal is a tuned circuit, that's why a crystal oscillator works. It is a low impedance series LC circuit at one frequency and a high impedance parallel LC circuit at a near frequency. If you use a crystal as a filter, its bandwidth is so narrow that it wouldn't receive much...
  18. audioguru2

    SAW filters

    Hi Kevin, SAW filters have been popular for awhile for their use in cable TV boxes, TV transmitters and TV sets. In the olden days, those systems used many tuned LC filters to achieve the "funny response" that is required for sharp cutoff of the side of the picture carrier that isn't transmitted...
  19. audioguru2

    The simplest audio amplifier

    Hi Kevin, 1) What is an "auto stereo amplifier"? Car amp? Automatic amp? 2) What does he want to do to it?
  20. audioguru2

    "Power?" Inverter

    Hi Ante, It should be obvious that the capacitors in this project are backwards. The collector of each NPN transistor goes much more positive than its base.
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