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  1. audioguru2

    Driving a HDD motor

    A hard drive operates from a 12V supply. The motor might survive 15V for short periods. I don't have a list of Mosfet substitutions. I just select a Mosfet that is available from a list of them that have the spec's I need.
  2. audioguru2

    Slow power up effect

    An opamp can drive a voltmerter as slowly as you want. But the opamp would need a supply voltage anout 2V higher than the max voltage the meter is measuring.
  3. audioguru2

    noisy power supply line

    Your amplifier is amplifying the power supply noise. But you forgot to attach the schematic of the amplifier for us to see why.
  4. audioguru2

    Slow power up effect

    Hi Daisy, If the meter is actually a current meter with a series resistor converting it to read volts, then just add an electrolytic capacitor in parallel with the meter to slow it down.
  5. audioguru2

    Help me to understand the MC3359P IC

    Hi Walid, Your transmitter and your radio circuit are very different: 1) The transmitter is wideband and the radio is narrowband. If something doesn't work properly then you don't have another narrowband station to test your radio with, and you don't have another radio to try the modified...
  6. audioguru2

    Look at this current mode Power amplifier!

    Hi Shariar, Sanyo's STK hybrid power amplifiers are used in cheap old stereo systems. I haven't seen any new and good ones. National Semi make the LM3875 and LM2886 power amplifier ICs that have up to 68W and are excellent. Look in Google for Gain Clone Amplifier. Here is a project for them...
  7. audioguru2

    Look at this current mode Power amplifier!

    Hi Shahriar, To measure the harmonic distortion of an amplifier you load it then feed it a pure sine-wave and adjust the level so the output is just below clipping. Then the distortion analyser is calibrated so that the amplifier's output is at 100%, and a notch filter is added to remove the...
  8. audioguru2

    Help me to understand the MC3359P IC

    Hi Walid, Our new Disco-light project has a limiter circuit "stolen" from Elliot Sound Products. I haven't tried it so I don't know its range and distortion:
  9. audioguru2

    Help me to understand the MC3359P IC

    I don't know how narrow is the bandwidth of wireless telephones. It might be only 6kHz. Broadcast AM stations are only 10kHz apart so their bandwidth is about 8kHz. Broadcast FM stations have a bandwith of 150kHz. My transmitter doesn't have a limiter so if you are too loud into its mic its...
  10. audioguru2

    UPS & Inverter

    Our Low Cost 500W Inverter project was modified 2 years ago and works very well in The Philippines driving tube lights, fans and multi-voltage TVs. But it was recently changed and might blow up. Normal? Have you ever seen a 230V/12V/50A transformer? Made for a welding machine or something that...
  11. audioguru2

    Look at this current mode Power amplifier!

    Hi Shahriar, 1) You have an opamp that has phase-shift, a current sink circuit and a power transistor that also have phase-shift. They are inside the negative feedback loop of the first opamp that also has phase-shift. That is how to make an oscillator. It might work if the 1st opamp has a...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    I put the ammeter inside the negative feedback loop so its resistance doesn't ruin the very good voltage regulation of this circuit. If the meter's resistance is 0.1 ohms then it would reduce the voltage 300mV at 3A if it was placed after point 3.
  13. audioguru2

    Help me to understand the MC3359P IC

    I forgot to say that this radio circuit is for narrow-band FM (telephone quality). My FM transmitter is for wideband high fidelity FM (broadcast quality). A narrowband radio will receive wideband signals with extreme distortion. Kevin. Nearly all FM radios use a 10.7MHz IF amplifier. The FM...
  14. audioguru2

    Help me to understand the MC3359P IC

    No Kevin, Hi Walid, The IC circuit is only part of a radio. The "front-end" of a super heterodyne radio is missing. The front end is the RF amplifier, local oscillator and RF mixer that converts the RF signal to the 10.7MHz IF (intermediate) frequency that is easier to amplify and filter than...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original project might work with a 24V/1A transformer but its ordinary opamps will be operating with a supply voltage higher than their absolute max rating. If the opamps survive then the low output voltage indicates that maybe a transistor or diode is connected backwards.
  16. audioguru2

    Stun Gun from Camera Flash

    People are killed from the high power of stun guns. Make something peaceful.
  17. audioguru2

    circuits

    If your soldering iron doesn't have a transformer and isn't a soldering gun, then a 1N4005 rectifier will cut its power in half. Connect the rectifier in series with one of its two wires and connect a switch across the rectifier to switch to full power.
  18. audioguru2

    Stun Gun from Camera Flash

    A stun gun is a weapon. I won't show anybody how to make a weapon.
  19. audioguru2

    circuits

    Radio circuits don't work if their capacitance or inductance is too high: 1) Wires on a circuit beside each other have capacitance between them. The capacitance is higher when the wires are longer on a bigger circuit layout. 2) Wires have inductance that is higher when the wires are longer on...
  20. audioguru2

    UPS & Inverter

    Tube lights (fluorescent lights?) and fans usually don't need a sine-wave. A simple square-wave circuit is much easier to make than a sine-wave circuit. An inverter generates fairly high voltage AC from a battery. A UPS charges its battery, generates AC the same as an inverter and either runs...
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