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  1. audioguru2

    Question about Ground Loops

    CAUTION! I don't know why you want to measure the resistance between two "grounded" chassis, but make absolutely certain that the electrical outlets are wired correctly. If the electrical outlets and the equipment are wired correctly and their insulation is good, then there won't be any current...
  2. audioguru2

    Check this Out.. FREE!!!

    Did you find 22 other gullible people to signup and buy stuff from their advertisers? Isn't your "free" plazma TV a refurb? Did it work? They say their scam isn't a piramid scheme. You buy stuff and refer 22 people who buy stuff and each of them refers 22 people who buy stuff and each of...
  3. audioguru2

    its been kind of .....DEAD lately...

  4. audioguru2

    100W Audio Amplfier By Smart Kit

    There is a very simple 60W Guitar Amplifier in our projects section that isn't very high-fidelity: http://www.electronics-lab.com/projects/audio/031/index.html There are many good amps on this site:  http://www.sound.westhost.com/projects-1.htm I hope you can find the parts in your "market".
  5. audioguru2

    its been kind of .....DEAD lately...

    Hi Eceto, What should we talk about? I've been busy on other electronic chat sites and I am busy designing and making a new project. ;D
  6. audioguru2

    100W Audio Amplfier By Smart Kit

    R2 and R16 will not get hot if the pot is adjusted for an idle current for the amplifier of only 50mA. They will heat normally if the amp is playing loudly. Many parts affect the current through R2 and R16, and the current through Q1 and Q9. The current source Q10 is supposed to provide 7mA so...
  7. audioguru2

    car + mp3 + powersupply + noise HELP!

    The amplifier, power supply and MP3 player's audio output cable's shield should all be grounded at a single point. Maybe your power supply is coupling 12V noise to the input of the amplifier through the audio cable's shield. Try connecting the power supply's ground to the amplifier's ground and...
  8. audioguru2

    15A Lead Acide Battery Charger!

    Old-fashioned "add water" lead-acid batteries were fully charged at 13.8V. New "maintennance-free" sealed car batteries are different and are fully charged at 14.4V. Measure the voltage of the battery that is charging by the alternator on a new car. I don't think anyone makes "13.8V" batteries...
  9. audioguru2

    100W Audio Amplfier By Smart Kit

    The BDW84A will blow-up in this circuit because its voltage rating is too low. Go to www.farnell.com and look for your country's flag. They have online electronic parts ordering in many countries. Can't you buy a Smart-Kit there? They are from Greece but I can buy them here in Canada, nearly on...
  10. audioguru2

    Low-pass Filter?

    The opamp provides the majical gain for some positive feedback and boost. In my example of a Sallen-Key lowpass 2nd-order filter that has equal component values: 1) At low frequencies, C1 and C2 have a high impedance and don't affect the response which is flat. 2) At high frequencies, C2...
  11. audioguru2

    car + mp3 + powersupply + noise HELP!

    You need to ground the MP3 player and its power supply at the amplifier, not at the battery.
  12. audioguru2

    9v to 6v DC/DC Converter

    You can't use a 7806 regulator nor an LM317, because they need more than 8V or 9V at their input to regulate properly. You can't use a 6V zener diode because it wastes power and its regulation fails as the battery runs down. The problem is that the voltage of a 9V alkaline battery quickly drops...
  13. audioguru2

    Electronic Stethoscope

    Hi Xoy, Mylar is a plastic film. A mylar capacitor is a metalized plastic film one. It is fine. I spec'd metallized plastic film caps so people wouldn't use ceramic caps that have a very wide tolerance (+80%, -20%). My European plastic caps have a 5% tolerance. ;D You could use Oriental "green...
  14. audioguru2

    Low-pass Filter?

    A FIR digital filter in a DSP board has a sharp cutoff because it effectively has many orders. A Butterworth analog filter can also have many orders. Maxim have some Butterworth switched capacitor lowpass filters with 8 orders. Square wave in, sine wave out.
  15. audioguru2

    100W Audio Amplfier By Smart Kit

    Your substitute transistors BD825 and BDW84A are rated for only 45V! They will blow-up in this 80V circuit! The original transistors are rated at 80V. Where in the world are you that you can't get common parts?
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    I betcha it is for the mains elecrical wiring's earth connection if needed. Then you connect the project's positive output to it and the 0V terminal becomes negative. ;D
  17. audioguru2

    Low-pass Filter?

    An FIR is a complicated digital filter. Maybe you are thinking of a switched capacitor filter, like I use in my ultra-low-distortion signal generator. I even use a switched capacitor notch filter in my distortion analyser circuit. They make great simple filters. ;D
  18. audioguru2

    Low-pass Filter?

    The gain doesn't fall off too soon because the positive feedback boosts it near the cutoff frequency. For a Butterworth filter, the frequency response is absolutely flat to near the cutoff frequency, no matter how many orders there are. As an example, I use a 2nd order highpass Butterworth...
  19. audioguru2

    Low-pass Filter?

    The math is in a text book or on the web. Here's an example of a Butterworth lowpass filter showing the positive feedback:
  20. audioguru2

    stroboscope

    Hi Dito, Just make two 555 oscillators. The fast one pulses the LEDs and the slow one gates the fast one on and off by connecting its output to a voltage divider (to the positive supply) to provide a high enough voltage for the reset pin of the fast one. I've made many LED "strobe" things that...
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