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  1. Audioguru

    FM & LED shop lights

    I never bought a Radio Shack tuner but I did buy two sets of their speakers. The Minimus 7 speakers had a 4" woofer and very nice dome tweeter in sealed enclosures but the "30W" rating of the woofers was revealed when they burnt out. The woofers were stamped 5W Korea. The second set of Radio...
  2. Audioguru

    Hi, have anyebody had trouble building the ELENCO 108 AM/FM RADIO KIT

    Years ago, at work I won two Sony portable FM stereo Walkmans that play through headphones. I live in a big city and they are missing RF AGC so they are overloaded by the many strong radio stations. They have a "local-distant" attenuator switch to pickup the local stations without overload but...
  3. Audioguru

    Amp for Visaton FR 13 4 ohm speaker

    The datasheet for the cheap little speaker shows that it produces no bass and has a shrieking peak at 5kHz. The ebay amplifier has no detailed spec's so its distortion might be awful and its "30W" might be a lie. If the speaker enclosure is not designed for the detailed spec's of the speaker...
  4. Audioguru

    FM & LED shop lights

    Static is AM interference that is ignored by a half-decent FM radio. A cheap FM radio picks up and plays a lot of AM crap.
  5. Audioguru

    Flashing joule thief - beginner

    I did not see any details about how to make the transformers. Many Instructables are designed by kids who are only 10 years old and who know nothing about electronics. The blinking LED might be part of another circuit that was purchased, not made.
  6. Audioguru

    Yamaha Stereo transformer

    The stereo probably has a label saying how much is its maximum AC current. If the current is not stated then its maximum RMS output power will be in its owner's manual. Then you guess that the amplifiers are class-AB and the heating is 45% of the maximum output power Then you use simple...
  7. Audioguru

    JFET Power Amplifier With Output Transformer

    We didn't talk about RAP "music" yet.:) Usually RAP is a guy (rarely a girl) reading a book in a monotone with a drum beat in the background.
  8. Audioguru

    JFET Power Amplifier With Output Transformer

    Musicians prefer a hifi amplifier that is wideband and has very low distortion. Electric guitar players prefer the muffled old distortion of a tubes amplifier so the noises sound like 60 years ago. Your schematic in the first post shows a class-AB amplifier with the output devices biased so...
  9. Audioguru

    JFET Power Amplifier With Output Transformer

    Decibels are used to measure noise (hum and hiss) and frequency response. A good amplifier has no noise and a response that is flat from 20Hz to 20kHz. 0.1% distortion is at -80dB. An undamped speaker sounds like a bongo drum and also has higher frequency noises. A well damped speaker does...
  10. Audioguru

    Hi, have anyebody had trouble building the ELENCO 108 AM/FM RADIO KIT

    "BORIGN"? This is dyslectic for BORING. Maybe the Elenco kit manufacturer has dyslectic employees writing the assembly instructions. Many years ago I made an Eico FM tuner kit that used vacuum tubes then later when FM stereo was invented I made a stereo multiplex decoder for it. They worked...
  11. Audioguru

    JFET Power Amplifier With Output Transformer

    Modern audio opamps (not a lousy old 741 or LM324) are perfect tor sound. Tube amps had a low open loop gain and not much feedback because the output tubes and output transformer had a high phase shift therefore a poor damping factor and distortion 100 times more than modern opamps when new but...
  12. Audioguru

    Hi, have anyebody had trouble building the ELENCO 108 AM/FM RADIO KIT

    Are you using rosin core solder?
  13. Audioguru

    JFET Power Amplifier With Output Transformer

    Most excellent audio amplifiers use or are built like an opamp with an open-loop gain of 200,000 to a few million. Then when negative feedback is added to reduce the gain to about 30, the distortion is so low it cannot be heard and is difficult to measure. Audio opamps (OPA134 distortion is...
  14. Audioguru

    JFET Power Amplifier With Output Transformer

    No. Even harmonics are produced when the top half of the signal is not symmetrical with the bottom half like in an old room-heating class-A amplifier. Your signal's top and bottom halves are symmetrical so when clipping the distortion is odd harmonics (push-pull class AB). Some people think that...
  15. Audioguru

    JFET Power Amplifier With Output Transformer

    Your clipping is soft like an old vacuum tubes with output transformer amplifier, maybe because the high frequencies are missing. Since you like distortion, haver you ever built a Hendrix Fuzz Face distortion-making pedal circuit? 55 years ago I built a kit vacuum tubes stereo amplifier (25W...
  16. Audioguru

    Peak detector for piezo drum pad

    Does your drum produce radio frequencies? One opamp has a gain bandwidth of 1MHz (middle of the AM broadcast band) and the other is 4.5MHz on the shortwave band. I think you are making an electronic piano like my kids had 30 years ago but theirs used pushbuttons tp play the notes and yours uses...
  17. Audioguru

    JFET Power Amplifier With Output Transformer

    Correct. I did not know that I was normally deaf to high frequencies. The hearing aids made a remarkable good change to my life. An amplifier that is clipping produces squarewaves. A buzzer also produces squarewaves but not music. An amplifier with vacuum tubes had to use an output transformer...
  18. Audioguru

    JFET Power Amplifier With Output Transformer

    Hi frequency hearing loss is normal for old people (men over 30) and for people who ruined their hearing with loud acid rock sounds, guns or loud motorcycles. Then they use way too much distortion because they do not hear all of it. "Good Enough"? An AM radio or an old wired telephone is good...
  19. Audioguru

    JFET Power Amplifier With Output Transformer

    EEK! I am a hifi guy. I hate distortion if it is produced by clipping or class-B crossover, even harmonic or odd harmonics. You are even cutting low frequencies which makes the distortion sound louder and you have an awful output transformer that mutes high and low frequencies and has its own...
  20. Audioguru

    Peak detector for piezo drum pad

    What is the function of the peak detector? To show the amplitude of the peak voltage on an LED bar graph? You showed a graph of an unfiltered 12Hz piezo strike that has time on the horizontal but simple numbers on the vertical. Are the numbers the voltage? The vertical has a DC offset. Where...
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