Search results

  1. audioguru2

    FM Radio

    My cable-TV company changed all pay-per-view to the digital channels years ago. In 1980 I modified my TV to unscramble the scrambled analog signals. My circuit was a lot more than just a variable capacitor since the sync was suppressed at certain times and needed to be detected, made then...
  2. audioguru2

    FM Radio

    I think the varicap diode was backwards, then it got reversed recently, then it got reversed again recently. It is odd that the schematic doesn't say anything about the "correction".
  3. audioguru2

    Low-pass Filter?

    An electric motor is an inductor. AC current through an inductor is filtered, so a square-wave will have some of its edges smoothed off.
  4. audioguru2

    Low-pass Filter?

    Hi Farhad, A square-wave or modified sine-wave inverter should power an AC electric motor fine at its full speed. I have read on the web that an electronic motor speed control won't work properly unless the waveform is a true sine-wave.
  5. audioguru2

    Audioguru FM Tx

    Hi Sssaaa, The circuit you posted uses a crystal in an odd oscillator circuit. Since a crystal cannot be frequency modulated very much then the transmitter must be narrow-band for a ham radio receiver. It also doesn't have pre-emphasis like radio station FM transmitters use. 250mW is probably...
  6. audioguru2

    Power supply for amps

    Ampslab tempts you with their circuit and its good spec's, because they want you to buy their kit. It is probably a good deal.
  7. audioguru2

    Power supply for amps

    Maybe you didn't drive it higher than 68W into 4 ohms. You don't have a circuit to limit its output power, so it might exceed 68W then its SPiKe protection circuit will become active. They say that the protection circuit really messes up the sound and it sounds horrible. It will be fine with a...
  8. audioguru2

    Power supply for amps

    A guy called Gevv joined our forum a few months ago and posted many projects with the RAR file type, and having a password I think is gevv. I saved some of his projects and many are amplifiers using the LM3886, some paralleled. EDIT: This file is without a password and has a 100W into 4 ohms...
  9. audioguru2

    RF transmitter

    I am a retired old geezer. ;D I just relax all day, every day and bum around the internet and my town.
  10. audioguru2

    Low-pass Filter?

    I think the power supply current for an unloaded 500W inverter would be around 4A or even higher if your transformer doesn't have enough inductance. Your little 3A supply was too weak.
  11. audioguru2

    Audioguru FM Tx

    The modified circuit's power supply current is 84mA. Minus about 5mA for the oscillator and mic preamp leaves 79mA for the 2N4401 output transistor. Therefore the 2N4401 dissipates 100mW in RF and 611mW in heat. Its absolute max heat dissipation rating is 625mW so it is ready to smoke. To...
  12. audioguru2

    FM Radio

    Sarma is talking about the BB329 varicap tuning diode that is backwards in our project. It is supposed to be reverse-biased but is shown connected with forward bias. Nice going, Sarma, you have good eyes. ;D
  13. audioguru2

    RF transmitter

    Your "standard" Colpitts oscillator feeds positive feedback from the collector to the emitter, in phase. The telephone bug Collipitts oscillator feeds the inverted signal of the collector. C1 and C2 have their junction grounded, but since they are in series across the coil, their ends are with...
  14. audioguru2

    Power supply for amps

    An active crossover circuit for a car might use a single 12V supply and an output coupling capacitor. When power is turned on or off then the coupling capacitor will charge or discharge and make a loud "BANG" in the sound system. A home active crossover circuit will probably use a positive and...
  15. audioguru2

    Low-pass Filter?

    You wired the transformer so that the 12V windings cancel, instead of adding. Connect one 12V wire to the other winding's 0V wire. Then you will have a 24V center-tapped transformer. Look at my sketch. It won't be shorted the way you wired it. It just won't work. What does it do that makes you...
  16. audioguru2

    (EMF) Electromagnetic field detector

    Steven uses his to detect UFO's flying around his place at night. ;D
  17. audioguru2

    RF transmitter

    Look up Colpitts Oscillator in Google.
  18. audioguru2

    Power supply for amps

    What is "an active car audio amp"?
  19. audioguru2

    pyrometer

    In my circuit I used a 100k resistor as the load for the photo-diode. Without light or IR, then the input voltage to the opamp through the 100k resistor is 0V. I used a non-inverting opamp circuit with the extremely high input impedance of the FET in the input of the opamp, and it has voltage...
  20. audioguru2

    pyrometer

    I don't know why you have two photo-diodes in your 2nd circuit. Their outputs cancel. 1) In your 1st circuit, R1, R2 and R3 are not required. 2) The photo-diode doesn't have a load which should be a 100k resistor to ground. 3) The two transistors are also not required since the photo-diode and...
View older results
Top