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  1. Audioguru

    I'm Back- sort of

    On another website, somebody is buying 1000 cheap diodes from Amazon. Somebody else said that the Amazon seller is buying cheaper diodes (more defectives and fakes) from ebay and re-selling them on Amazon. Today, digikey.ca in Canada has 9100 TL081CP opamps from Texas Instruments for $0.86...
  2. Audioguru

    I'm Back- sort of

    Since Amazon and their seller know nothing about electronic parts and the manufacturers of the diodes are no-name-brand then some of those diodes might not work and should be tested.
  3. Audioguru

    I'm Back- sort of

    200k feeding the 1k resistor to ground produces a gain of 201 times. 180k makes 181 times and 220k makes 221 times. The 10% difference will not be noticed. Try the 220k.
  4. Audioguru

    I'm Back- sort of

    Doesn't your power amplifier have an input volume control? A guitar or a pedal has a volume control that is near you to be adjusted while you are playing the guitar.
  5. Audioguru

    I'm Back- sort of

    With a gain as high as 201 times and without diodes to limit the output swing to 1.2V peak-to-peak, the opamp output will be 7V peak-to-peak (when the opamp supply is 9V) that might overload your amplifier input, because the opamp output will be clipping like crazy making squarewaves. An opamp...
  6. Audioguru

    I'm Back- sort of

    The gain of the opamp is needed to overdrive the diodes for them to produce clipping of the signal or so that the output of the opamp produces clipping. Use as much gain as you want. You might like the sound of the opamp clipping like crazy without the diodes.
  7. Audioguru

    I'm Back- sort of

    Please show a schematic with all parts values. Maybe the input resistor value is too low and reduces the pickup output. The 220nF capacitor to ground in series with the 10k resistor at pin2 cuts 73Hz at -3dB (half the output power). Use 470nF for -3dB at 34Hz. If the resistor from pin2 to the...
  8. Audioguru

    I'm Back- sort of

    The voltage of pin1 is as high as it can go but should be at half the supply voltage. Here is my guess why:
  9. Audioguru

    Amplifier Alpine ra60f

    The car amplifier produces 100W RMS into 4 ohms per channel or 150W into 2 ohms. At 1% distortion and when the battery is charging at 14.4V.
  10. Audioguru

    I'm Back- sort of

    Squarewaves sound like squarewaves don't they? I think the small difference between all the opamps is caused by their different input resistances. The diodes in the negative feedback produced "soft" distortion and the diodes at the output of the opamp to ground and the opamps themselves (when...
  11. Audioguru

    I'm Back- sort of

    With a guitar pickup feeding an opamp with a gain of 201 times and with nothing (no gain control) to limit the opamp output voltage then the opamp output will be severely clipped squarewaves with a level so high that the speaker amplifier volume control might be difficult to turn down. If the...
  12. Audioguru

    I'm Back- sort of

    You are making a simple preamp for the guitar pickup. Since the circuit has no distortion diodes to reduce the level and has no volume control then you should use low gain in the circuit to prevent the output of the opamp from producing massive clipping if you play the guitar loudly. My...
  13. Audioguru

    I'm Back- sort of

    Here is the same opamp circuit you had before but without the pots and diodes:
  14. Audioguru

    I'm Back- sort of

    A properly biased opamp produces no distortion until it is turned up to severe clipping. Diodes produce "soft clipping" at a fairly low level.
  15. Audioguru

    I'm Back- sort of

    I simulated the simple overdrive circuit. Its output level is high when it is driven from a low impedance signal source. Its input impedance is too low to be driven by a guitar pickup. It reduces the pickup output level especially at high frequencies because its input impedance is about 33k ohms...
  16. Audioguru

    I'm Back- sort of

    Almost all opamps have a typical voltage gain of 100,000 at DC. But the maximum gain in pedal circuits is only about 1000 times less. The new distortion pedal you posted is the same circuit as you had before but re-arranged: 1) Dual-polarity power supply. The other one had the opamp biased at...
  17. Audioguru

    I'm Back- sort of

    What a mess of wires all over the place! Why don't you use perforated stripboard instead? Sayal sell a good one. The parallel strips of copper tracks and a few short straight jumper wires form half of a pcb and the parts for the remainder. It is easy to see what connects to what. the parts can...
  18. Audioguru

    I'm Back- sort of

    C3 passes AC audio but blocks the DC on the opamp output from frying the volume control that should never have any DC on it. It is normal for C3 to take a few seconds to charge then produce 0VDC at its output. The sudden DC when the circuit is powered produces a POP in the audio.
  19. Audioguru

    What is the typical mAh capacity of a 9v?

    The size and weight of that "6800mAh" 9V battery say it is only 600mAh to 1200mAh like all the others. The No-Name-Brand others also might be lying about their capacity.
  20. Audioguru

    I'm Back- sort of

    Electrosonic and another electronic parts supplier were near Sayal in Scarborough for years but now they are gone. Amazon and their sellers know nothing about electronic parts so they buy the cheapest from "over there" which are fakes or defective junk. Digikey and Newark are real online...
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