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  1. Audioguru

    Need help determining orientation of FET package in drawing

    You must learn the details about FETs: 1) A Jfet has an N and P junction and is "depletion" type that is turned on hard with no bias voltage and is pinched off when its gate-source has reverse bias. 2) A Mosfet does not have a junction and is "enhancement" type that is turned on hard when its...
  2. Audioguru

    Need help determining orientation of FET package in drawing

    The FETs are junction Jfets, not Mosfets. Some Jfets are symmetrical so that the D and S can be swapped without changing the spec's.
  3. Audioguru

    How do I make my own musical instrument?

    Most of us on this Western website forum know nothing about a Mridangam that is played in India. Wouldn't an electronic version be a project on a website forum in India?
  4. Audioguru

    Multivibrator of varying frequency

    I disagree. The capacitors quickly turn a transistor off and the base resistor turns it on then the capacitor has discharged and begins charging in reverse to about +0.7V.
  5. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Maybe your output transistors are leaky. The output of U2 should go from about +30mV to about -30mV and the output of the circuit with a load should be adjustable down to 0V. Check the input pin 3 and the output pin 1 of U2 for 0V. The output of U2 will normally go negative when trying to reduce...
  6. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    RV2 is supposed to be 20k (not 5k) sets the amount of gain for the output amplifier so it calibrates the output voltage to be 30.00V when the voltage is set to 30.0V. RV1 adjusts the output to be 0.00V when the voltage is set to 0.0V.
  7. Audioguru

    Power source for smoke detector

    There are some immigrants here who have family members living in the garage and maybe even in the attic. People born here have raccoons living in these places.
  8. Audioguru

    How to make this circuit unity gain?

    When a few hundred Watts amplifier is put in a car, some people add a huge capacitor since the battery can supply only (!) 600A.
  9. Audioguru

    Power source for smoke detector

    The voltage from a loaded battery drops gradually at first then drops quicker and quicker as it becomes dead. The voltage of a loaded capacitor drops quickly at first then drops slower as it becomes dead. you do not want that. A smoke detector detects low battery (maybe 7V) then causes a beep...
  10. Audioguru

    20-30V input 12v high current output regulator, not working

    When a transistor has a minimum gain of 20 then why assume its gain is 50? Don't you want every circuit made with that transistor to work or only a few of the circuits made with it to work?? I design everything with "worst case" parts (minimum gain calculations) so that every circuit works...
  11. Audioguru

    Audio troubleshooting

    Hum is a low frequency. Buzz is a higher frequency and hiss is a very high frequency. A tweeter does not produce low frequency hum.
  12. Audioguru

    20-30V input 12v high current output regulator, not working

    You do not want Rb to produce a substantial voltage drop. It simply limits the base current in the BC556 when the output is shorted to ground. Ra should be used to limit the current in the BC556 instead. I recommended a current of 30mA in the regulator because your 10mA is too close to the 6mA...
  13. Audioguru

    How to fix voltage drops at 220V in this inverter Circuit

    When one IRL540 Mosfet conducts 20A then its voltage loss across it is 1V. Then the transformer gets 11V instead of 12V. But the unknown transformer probably has a design of 220V input to make 14V unloaded output or 12V output at its full load of maybe 20A. Then the 11V from your circuit into...
  14. Audioguru

    20-30V input 12v high current output regulator, not working

    A BC556 has a current gain of from 110 to 800. Only some might have a gain of 800. A BC556C has a current gain of from 420 to 800. The regulator warms with only (18V - 12V) x 10mA= 60mW in your circuit but it is allowed to be fairly hot at 600mW. Why not allow it to conduct 30mA? Change R1 to...
  15. Audioguru

    Frequing resonance at audio taper

    A tone control circuit usually boosts and cuts bass and treble frequencies. Some tone controls have a mid frequencies boost and cut. Nothing "bends", instead the tone controls have a frequency where they begin boosting or cutting and for bass and treble tone controls this frequency is usually...
  16. Audioguru

    Differences between two diodes?

    Alibaba, ebay and maybe Amazon are Chinese and maybe have a translation problem or they know nothing about electronics.
  17. Audioguru

    Hello, varactor(varicap) formula help

    ALL electronic parts are not made exactly the same. Some are typical (or nominal in some datasheets), some are minimum and some are maximum even if they have the same part number. The datasheet lists the range from minimum to maximum and the typical (nominal) value for some spec's. You need to...
  18. Audioguru

    Simple Passive Stereo Mixer

    Do you understand what an attenuator is? You have five signal sources that are probably each the low output impedance of an opamp. One signal comes into one of your 4.7k resistors but it is loaded with the other four 4.7k resistors in parallel. Then the four resistors result in 4.7k/4= 1175...
  19. Audioguru

    GE Classic Radio Player 7-4135 schematic and amp question.

    Since the original radio has a cheap little speaker and the enclosure is not even designed for a speaker then I think the radio's electronics is also cheap and will produce no bass and maybe also no sizzling highs with a good external amplifier and speaker. BUT, I purchased a cheap but Name...
  20. Audioguru

    Simple Low Frequency Sound Generator

    I think an empty skull resonates better than a full skull, if you know what I mean.:)
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