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  1. Audioguru

    I'm Back- sort of

    I have bought a few things at Sayal. They are an electronics liquidator from India. I bought some Sylvania clock radios tor $1.75 each. I souped up low frequencies of one with larger capacitors and connected a 2-way speaker (6.5" woofer in a ported enclosure and a dome tweeter) making it hifi. I...
  2. Audioguru

    I'm Back- sort of

    Wrong thread??
  3. Audioguru

    I'm Back- sort of

    Now you swapped the output pin6 with the +power supply pin7. Even if the opamp did not release its magic smoke, it is probably ruined.
  4. Audioguru

    I'm Back- sort of

    An RC4558 or your Japanese version is a dual opamp with a few slightly better specs than a 741 opamp. One that has maximum input bias current will cause the output to be 4.0V instead of 4.5V.
  5. Audioguru

    I'm Back- sort of

    I just noticed that the small value of 0.22uF for C28 produces a -3dB cutoff at 727Hz and cuts all lower frequencies. No bass.
  6. Audioguru

    I'm Back- sort of

    You are using an old 741 opamp in a circuit designed for a newer TL081 Fet-inputs opamp that has no input bias current. The datasheet for an old 741C opamp says that its maximum input bias current is 500nA. Then the 1M input resistor would cause the voltage at pin3 to be 4.0V instead of 4.5V. A...
  7. Audioguru

    I'm Back- sort of

    Your voltages are wrong. I think the voltages are wrong because the 741 opamp is a fake or is defective and has way more input bias current than the original TL081 opamp.. Oh, maybe your voltmeter is an old one with a low resistance? Pin 3 is the +input that is fed half (+4.5V) the supply...
  8. Audioguru

    I'm Back- sort of

    Obviously, voltage is measured when the opamp is powered. With your 9V supply, the maximum output of a 741 opamp is about 8.0V but you measured 8.9V so something is almost shorted to the +9V, especially since the output should have been +4.5V.
  9. Audioguru

    I'm Back- sort of

    You measured the output voltage of the opamp when it has no load. The voltage you measured is too high to be possible. Because something went wrong to cause the voltage to go almost to +9V when it should have been +4.5V. The output voltage of an opamp will be reduced when it has a load. The...
  10. Audioguru

    I'm Back- sort of

    The output voltage of an old 741 opamp cannot be higher than about 1V less than its supply voltage when it has no DC load. Your supply is 9V and you said the output pin 6 was 8.9V which is impossible. The DC output voltage is controlled by the inputs voltages. Measure them. The + input should...
  11. Audioguru

    I'm Back- sort of

    Sparky Cal, the schematic of your distortion making pedal circuit shows a single opamp with the pin numbers of a single opamp. BUT you are using a dual opamp with different pin numbers. That is probably why your circuit does not work.
  12. Audioguru

    I'm Back- sort of

    Yes. With a positive and negative power supply, the +input of the opamp is biased at 0V which is half the total supply voltage. With a single positive power supply then the + input is biased with a voltage divider at half the supply voltage.
  13. Audioguru

    I'm Back- sort of

    You must disable the unused opamp to prevent it from oscillating and causing interference. Connect its output to its - input and connect its + input to a half the supply voltage bias.
  14. Audioguru

    I'm Back- sort of

    The DC voltages are correct. Maybe you got a cheap fake opamp from "over there".
  15. Audioguru

    I'm Back- sort of

    You do not say if the prongs of your pots are pointing up or down. With no input signal, measure the DC voltages:
  16. Audioguru

    6.3vac heater windings

    When I was younger I used hand-me-down very expensive and high quality Shure phono cartridges from my wealthy friend and they produced the clicks and pops from vinyl records with good accuracy. Since it was a normal mechanical problem, I ignored the poor high frequency response and high...
  17. Audioguru

    6.3vac heater windings

    Since I am old then I played with vacuum tubes 60 years ago and see that a solid state amplifier is much better. Today some younger people might like to try old stuff like a vacuum tubes amplifier, an old car or an old TV.
  18. Audioguru

    6.3vac heater windings

    I made a Heathkit vacuum tubes amplifier 60 years ago. Every few months it produced distortion that measured 10% or more then I replaced the output tubes to make the distortion low. Tubes wore out so often that they were sold in convenience stores. Then I made a kit FM tuner that also had...
  19. Audioguru

    6.3vac heater windings

    Why are you using antique tubes?? Do you like their distortion, poor frequency response and poor speaker resonance damping?
  20. Audioguru

    I'm Back- sort of

    You do not understand. Look here:
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