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  1. audioguru2

    Amplifier stability and compensation

    Como estas, Rodeo, You already have a graph of how loop-gain varies with frequency. I marked it to make it clearer:
  2. audioguru2

    dynamic Resistance measurement of zeners

    Simply modulate a current source and measure the voltage change across the zener diode.
  3. audioguru2

    Sound To Light Box help

    4 or 6 pins dual-inline for each triac.
  4. audioguru2

    dynamic Resistance measurement of zeners

    Hi Sachin, Welcome to our forum. ;D To measure the RD of a zener, change the zener's current a measured amount a little above and below its operating current and measure the resulting voltage change across it caused by its dynamic resistance. Then use Ohm's Law to calculate the effective resistance.
  5. audioguru2

    Sound To Light Box help

    The circuit has a 9V isolation transformer probably because the box is metal. But the microphone could still be connected directly to 240VAC because I don't see opto-isolators driving the BTA08 triacs.
  6. audioguru2

    n-chanel enhancement mode power mosfet

    I told ya so!! ;D ;D
  7. audioguru2

    Sound To Light Box help

    Today you might measure 0V to ground on the microphone. Next week, with it plugged into a different mains receptacle that is wired incorrectly, the microphone might measure 240VAC. Mains powered devices must have an isolation transformer if you want to connect them to anything. Maybe it already...
  8. audioguru2

    To Find Working transformer

    Hi Miles, Some techies don't bother with the neon bulb and its resistor. They just use a hand to feel the high voltage spike. ;D
  9. audioguru2

    Sound To Light Box help

    Maybe you weren't grounded when you touched it. Maybe the mains receptacle it was plugged into was wired correctly (they all aren't). Without an isolation transformer it is deadly to connect anything to it.
  10. audioguru2

    Sound To Light Box help

    Hi Stuee, It might be Very Dangerous! The lightbox might be cheaply designed without an isolation transformer. The mic might be connected directly to one side of 240VAC.
  11. audioguru2

    240W Class-D surface-mount amp IC

    They have so many members on-line that a topic that you are looking at changes quicker than you can read it. ;D
  12. audioguru2

    TRANSISTOR ATTENUATOR?

    In a simple cross-coupled two transistor multivibrator the bases of the transistors are driven "below the supply" about half the time. In a two inverter Cmos oscillator the input of one inverter is driven beyond both supplies on each cycle. ;D
  13. audioguru2

    To Find Working transformer

    Hi, The easiest way to determine if a transformer will work OK is to weigh it. He, he. ;D A bad one will have its liquid core leaked out. You could always ask the transformer. ;D ;D
  14. audioguru2

    Warning Light

    Hi Tnk, You missed this part. The control logic uses very low current.
  15. audioguru2

    240W Class-D surface-mount amp IC

    Hi Miles, Modern audio amp IC's perform extremely well. At diyaudio.com guys are copying commercial IC amps that have very good sound. One commercial amp uses an excellent IC from National Semi. The IC costs only a few dollars but the amp is selling by the thousands for a few thousand dollars...
  16. audioguru2

    240W Class-D surface-mount amp IC

    Hi Miles, All car amplifiers are rated in Whats where the amp is clipping badly to make the numbers much higher. After all, a square-wave that has the same p-p voltage as a sine-wave produces double the amount of power. Their parts are also spec'd with a rediculously low impedance load of 2 ohms...
  17. audioguru2

    Warning Light

    You don't want to power anything from the voltage across the switch. Its current would fool the circuit to thinking the switch didn't open. :o
  18. audioguru2

    240W Class-D surface-mount amp IC

    Read the fine print: it's rated in Whats, not Watts. :o They even invented a special clipped input signal when it's pumping-out the square-wave Whats. At reduced output where it and the source aren't clipping, it would make a nice small amp to be hid inside a sub-woofer or something. You could...
  19. audioguru2

    240W Class-D surface-mount amp IC

    Hi Guys, They take a 4-channel class-D amp that operates its PWM at 385kHz, run the channels bridged to get a high-power stereo amp, then parallel those two bridged amps to get 240W output. Fairly difficult. Then they integrate the whole thingy into a tiny surface-mount package! The package...
  20. audioguru2

    TRANSISTOR ATTENUATOR?

    Hi Prateek, When the opamp has a gain of a few million, your meter across its inputs will read zero. In this inverting opamp circuit, the negative feedback in Rf cancels the signal in Rin.
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