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  1. audioguru2

    sound Card mic input standart

    Hi Hakyman, There isn't a standard for powering electret mics from sound cards. Some are wired for a 2-wire electret mic and others are wired for a 3-wire electret mic. Completely different. The output level of a mic is about 10mV but could be as high as a few hundred mV if you sing loudly...
  2. audioguru2

    electronic valve shower, do you have an idea???

    What a lousy life that would be. What about internet? I guess they could get shelter in a discarded washing machine. ;D
  3. audioguru2

    Electric Lock

    I did a job in the new head office of a major bank that was under construction. The contractor installed electric locks that unlock during a fire-alarm. :o The executives found-out how easy it would be to rob the place by pulling the alarm, and delayed the opening until the whole system was...
  4. audioguru2

    But can anybody tell me what is goin on in Silicon Chip website

    Hi Rhonn, You must know the exact name of the Silicon Chip project to find it on Google. ??? How do they allow you to see their whole article if you pay for it? Just give you a link to Google? ;D Their website projects archive goes back only about 5 years. :'(
  5. audioguru2

    Convert 12 volt DC to 120 volt AC

    I can buy a nice little 100W inverter for less than half the cost of a shaver. Why would anyone want to make a 4W inverter? ;D
  6. audioguru2

    Optical guitar pickup

    Hi Moeburn, Won't the string constantly cast its shadow on the photocell, so even when it is vibrating there won't be any output?
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi ElectroFreak, Welcome to our forum. ;D 1) If you build it according to our latest mods, it should work well and be reliable. But I don't think anyone has built it yet. 2) For a dual supply, most things need to be duplicated so just make two completely separate circuits and two transformers...
  8. audioguru2

    Convert 12 volt DC to 120 volt AC

    That's the simplest inverter circuit that I have ever seen! ;D 1) I can't picture what its waveform would look like. A spikey square-wave with its horizontal parts severely tilted? 2) Its frequency depends a lot on the inductance and saturation level of the transformer, a little on how much load...
  9. audioguru2

    Electrolytic cap polarity markings

    Hi Guys, What's going on today? For all my life I have marked the "+" wire on electrolytic caps of schematics and layouts. All my old Philips caps are marked "+" and "-". Now I realize that today's caps are marked with a line of negative signs, "------". Who changed it and why?
  10. audioguru2

    Capicitor Help

    It was hard to get to the pic, but the pcb seems labeled "L25" above it. "L" usually indicates an inductor. If it has a ferrite core then a magnet will ignore it. ;D 
  11. audioguru2

    Powering FM transmitter via USB?

    Hi Dazza, If the dropout votage is 3V then you need 5.9V input to get a "dropped-out" 2.9V output when it is designed for a 3V output. It is dropped-out when it is regulating poorly. You might be lucky and find one with a lower dropout voltage, or just use a two-resistor voltage divider feeding...
  12. audioguru2

    Powering FM transmitter via USB?

    Hi Dazza, Your transmitter probably has a filter cap across its power pins so nothing will feed past it into your computer. How are you going to drop 5V down to 3V?
  13. audioguru2

    n-chanel enhancement mode power mosfet

    I have a no-name-brand electric screwdriver that is over-geared so much that it takes it forever to drive a screw into wood. But when the screw is tight, the thing wrenches my arm off. They should have an automatically variable transmission like a few newer cars have. ;D
  14. audioguru2

    n-chanel enhancement mode power mosfet

    I wonder how many overvolts it takes to over-rev an unloaded motor to make it fly apart in pieces. ;D These little motors draw more than 5A when stalled. At 12V is that enough heat to fry my eggs for breakfast? Nah, the smoke would ruin the taste!
  15. audioguru2

    ??? Audio Expansion Circuit ???

    Hi Xtp, Many years ago I used compander IC's from Philips. Some are still available and they have a nice Compander Cookbook online. NE570 NE571 NE572 and more. ;D
  16. audioguru2

    n-chanel enhancement mode power mosfet

    You can't use the motor's high RPM unless your gearing matches it. You need a motor with high torque at the RPM it will be running at in your application. If you use a 6V motor with a 12V supply, its voltage and current are both doubled so it tries to produce 4 times its rated power. Guaranteed...
  17. audioguru2

    Amplifier stability and compensation

    Hi Rodeo, Here's how to power and bias the inputs of opamps:
  18. audioguru2

    Help needed building a radio transmitter/receiver system

    The BF494 RF transistor has very low capacitance and needs 10pF in this circuit, if I remember correctly since I haven't seen a BF494 for about 40 years! ;D
  19. audioguru2

    Help needed building a radio transmitter/receiver system

    C3 in the transmitter posted by John (HotWaterWizard) should be 10pF, not 10nF as shown. ::)
  20. audioguru2

    But can anybody tell me what is goin on in Silicon Chip website

    Hi Shahriar, If you know the name of Silicon Chip's project, enter it in a Google search. I just finished entering Micromitter in a Google search and got a link to their entire Micromitter article with schematics, pcb's, parts list and description. ;D
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