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  1. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    We are guessing that the speakers in the TV are driven with "bridged" amplifiers because joining the black speaker wires to the stereo headphones caused problems but using a single channel without joining the black wires was fine. A bridged output has an audio power amplifier driving each of...
  2. Audioguru

    help -- muh logic ended in ruins

    Without a schematic showing resistors and current we are just guessing. The datasheet for a 2N7000 shows that some of them barely turn on with a gate voltage of 3V and you tried a power supply that was 3V so how could it work? Other 2N7000 Mosfets try to conduct 600mA. With a supply voltage of...
  3. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    If there is no household electricity on the speaker wires when the AC electrical plug is plugged in one way and the reverse way then you do not need another transformer. An "audio" transformer probably cuts high and low frequencies. I told you that your headphones have a common ground wire for...
  4. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    Don't do it! If your TV does not have a power transformer then its wiring might be connected to one of the electricity wires in your house. If you connect the TV speaker wires to your stereo then the metal case and speaker wires of your stereo might also be connected to one of the electricity...
  5. Audioguru

    Is this a low pass filter?

    The speaker and its enclosure you are using as a sub-woofer cannot produce low frequencies because they are too small and the enclosure is not designed properly. Did you try the little speaker by itself to hear that does not produce low frequencies? A lowpass filter passes low frequencies that...
  6. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    Since you don't know what you are doing then don't do it. There might be a severe electrocution hazard if the TV does not have a power transformer. The circuit might be connected to one of the electricity wires. Since the speakers are tiny they cannot produce low audio frequencies so the...
  7. Audioguru

    Power supply series connection

    Ali is a Chinese company. They do not know how to speeky zee Engrish! They exaggerate! One place on their ad says, "Maximum power per channel: 130W", another place says, "100W + 100W" and another place says, "Channels: 1". They do not say one word about how much clipping distortion. They do not...
  8. Audioguru

    Power supply series connection

    No. The TDA7498 is a stereo amplifier that already has both of its two channels separately bridged. You cannot bridge them again into mono. In its datasheet I see nothing about 130W. I also see nothing about it driving a 4 ohm load, it shows 6 ohms and 8 ohms. Oh, the document for their...
  9. Audioguru

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

    You said the B+ is 41.6V. Then if R1 is -5% its resistance is 2090 and it dissipates (41.6V squared)/2090 ohms= 0.83W. Resistors are made to survive pretty high temperatures, your fingers aren't.
  10. Audioguru

    Power supply series connection

    You ain't getting 150W. The datasheet of the TDA7498 shows that it is overloaded with 4 ohm speakers but with your 31V supply its output per channel into 8 ohm speakers is 70W when it is clipping like mad with a horrible sounding 10% distortion. A graph shows 35W per channel at a more reasonable...
  11. Audioguru

    Not sure to be safe or sorry

    I have white LEDs with voltages from 2.3V (I couldn't believe it so I tested them twice) for some to 3.6V for others. There is no way they can be connected directly in parallel because the lower voltage leds will take all the current and immediately burn out, then the higher voltage ones will...
  12. Audioguru

    Not sure to be safe or sorry

    You show strings of 5 LEDs connected in series without a current-limiting resistor. If they are 3.3V white ones then they will begin to glow at 3V x 5= 15V and will burn out at about 17V. If they are 1.8V red ones then they will begin to glow at 8V and will burn out at about 10V.
  13. Audioguru

    Light chaser

    The Chinese schematic is wrong: 1) The minimum supply voltage for the NE555 is 4.5V so it might not work at 3V to 4.5V. 2) The output current from a CD4017 is only 3mA into an LED without a resistor when its supply is 5V and the current is less at lower voltages. Then the resistors are not...
  14. Audioguru

    AC Adapter Help

    Polarity of AC? Then it must point to the direction of the country it was made in.:)
  15. Audioguru

    Need help, regarding LED circuit

    It is a rip off.
  16. Audioguru

    AC Adapter Help

    The adapter is 7.2W or 50W. The switch is good for up to 1625W. Don't you think it will survive? The original adapter produced 24VAC but the Digikey one produces DC which is completely wrong. You need 24VAC at 7.2W but 10W will be fine. It must have the correct connector and polarity.
  17. Audioguru

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

    Why are you checking RV3? It controls the amount of maximum voltage set by the current setting pot P2 to pin 3 of U3 and its voltage was fine. But pin 2 voltage of U3 is wrong, not pin 3. With U3 removed then its pin 2 should measure 0V.
  18. Audioguru

    Power supply series connection

    If the outputs are DC and are completely separate (not each one grounded to earth) then simply connect the + of one of them to the - of the other to get 31V. Why do you need diodes?
  19. Audioguru

    AC Adapter Help

    ANY electronics parts distributor sells wall warts that are really called "AC/DC desktop, wall adapters". Digikey lists 7991 of them and you select voltages, current and connector. Digikey stocks two inexpensive "Foot Switch, gadget gizmos" that come with a cable.
  20. Audioguru

    Finding a nano amp transistor for Solar LED Light Marker

    The LED and its current-limiting resistor connects to the collector (not emitter) of the PNP transistor. The emitter connects to a voltage higher than the LED so about 5V for your 3.6V LED. I did not know that old germanium transistors are still available so its input must be about 0.2V and...
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