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  1. audioguru2

    circuit simulator

    Hi Prateek, When I worked for Philips, the 1st letter of a transistor's number is its material: A = germanium. B = silicon. C = gallium arsenide. D = indium antimonide. R = Devices without a semiconductor junction such as Hall generators and photoconductive cells. The 2nd letter ranges from A...
  2. audioguru2

    Sub for TL071

    Hi Rhonn, National doesn't make a single low-noise equal the the TL071 but they have a dual LM833 that is very low-noise and wideband for audio. It has transistors for inputs not the FETs of the TL07x series. ;D
  3. audioguru2

    circuit simulator

    Hi Prateek, About the only things I know that degrade a transistor's Hfe is allowing the reverse base-emitter voltage (about 5V to 7V) to be exceeded in a multivibrator or something, and too much heat. Sure transistors are troublesome when designing circuits for them. Cheap ones have a 9 to 1...
  4. audioguru2

    circuit simulator

    I can't remember how many hundreds or thousands of new transistors I have used over the years, and not a single one failed when used in a circuit that keeps the transistor working according to its guaranteed spec's. New transistors are very reliable so why bother testing them? Maybe if you want...
  5. audioguru2

    car battery charger

    I think that since it was drawing such a low current for such a powerful battery, it wasn't fully charged because the charger voltage was too low. I think that 200mA is a reasonable indication that such a big battery is fully charged. 200mA through its 0.22 ohm current sense resistor will drop...
  6. audioguru2

    car battery charger

    Hi Sasi, Then your battery is 14.5V when fully charged, not only 13.8V.
  7. audioguru2

    ??? Audio Expansion Circuit ???

    The professional wireless microphone systems I worked with use companders. The transmitters compressed the signal to raise its low-level parts well above the noise level, and the receivers expanded it back to normal dynamic range without noise. ;D
  8. audioguru2

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

    Hi Kain, That's great that it is nearly finished. A big fan will help cool it and blow away the smoke! ;D ;D
  9. audioguru2

    car battery charger

    Hi Guys, I'm still looking for information on the web about how much current a car battery draws when fully charged, to see if it is low enough to allow our battery charger project to automatically shut-off. I found out that car batteries are charged at a higher voltage today than they used to...
  10. audioguru2

    Another INVERTER we can talk about..

    How about operating the inverter at the TV's horizontal scan frequency with sync to the broadcast frequency?
  11. audioguru2

    Motorola Hi-Fi power amplifier

    Hi Guys, We have a nice new audio power amplifier project: http://www.electronics-lab.com/projects/audio/041/index.html I think the author makes an error when he says to put a current meter on the output and adjust the trimpot for zero current reading. I think the adjustment is to reduce offset...
  12. audioguru2

    Another INVERTER we can talk about..

    I see that the HV is regulated too, that's nice. ;D
  13. audioguru2

    car battery charger

    Hi Sasi, Thanks, you fixed it!  ;D The other people also complained that its voltage was too high at about 16.5V, no wonder the opamp never sensed that the battery was fully charged. The project's text and National's schematic doesn't say what should happen when the battery is fully charged...
  14. audioguru2

    Another INVERTER we can talk about..

    Hi Rhonn, Ferrite is used only for high frequency transformers, isn't it?
  15. audioguru2

    Sound To Light Box help

    Hi Stuee, My old TV didn't have external audio jacks and its chassis was connected to one side of the mains.  The microphone and circuit of your colour organ is connected to one side of the mains through the gates of the triacs. I used an audio transformer to feed audio from my TV with isolation...
  16. audioguru2

    car battery charger

    Hi Leo, Welcome to our forum. ;D The author of the project has many similar complaints about this project on his website. It just doesn't work! (Another one!) Since it is no longer made (for 10 years), did you use a substitute for the opamp? I think the LM301 opamp has its input common-mode...
  17. audioguru2

    Electric Lock

    I hate it when stairwell doors lock behind you. I was on the 56th floor and decided to use the stairs to get to the 55th floor instead of waiting for the elevator. It was a long walk all the way down to the ground. ;D
  18. audioguru2

    sound Card mic input standart

    Hi Hakyman, The output level of the stethoscope-2 project is much too high to feed a dynamic mic input on a sound card. I suggest you connect it to a line input. If a line input isn't available you can make an attenuator with two resistors and you don't need the LM386 stage nor the volume...
  19. audioguru2

    D4OD5 REPLACEMENTS

    Make that D40D5. (Forty, not 4 then the letter O).
  20. audioguru2

    sound Card mic input standart

    Hi Hakyman, With the stethoscope-2 project powered by 9V batteries, it max output voltage is about +4V to -4V which might be enough to damage the mic input of a sound card. The project's LM386 probably can produce enough current to blow any protection diodes on the sound card. :o
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