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Here is my circuit (to the best of my recollection):

schematic

simulate this circuit – Schematic created using CircuitLab

NOTE: The voltages and resistance values are not known to me and what you see in the schematic is just default.

Features:

  • Reverse feedback loop (I may mean "inverting" here)
  • LM741 opamp from Texas Instruments
  • Only two resistors used
  • This is a clipping circuit

My question is two-fold:

  1. What is the simplest configuration for building a headphone guitar amp using only an LM741 op amp and two resistors?
  2. Any idea why mine died after only 2 days of use?
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    \$\begingroup\$ are you sure the voltage source describes your actual circuit? Also, neither R1 nor R2 make sense... \$\endgroup\$ May 28 '18 at 16:47
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    \$\begingroup\$ The LM741 does still exist, but they're limited to use by hobbyists who don't know any better. The only thing they're useful for now is demonstrating op amp nonidealities, because they're very nonideal. \$\endgroup\$
    – Hearth
    May 28 '18 at 16:51
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    \$\begingroup\$ There's several possbilities for what killed your 741 so many years ago. Connecting the battery backwards, driving the headset directly from the opamp without a coupling capacitor (DC short circuit from output through the head phone,) etc. No way to tell after over 20 years. \$\endgroup\$
    – JRE
    May 28 '18 at 17:01
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    \$\begingroup\$ Thanks to this forum, I am getting served advertisements for TI LM741s. Thanks, guys. \$\endgroup\$ May 28 '18 at 17:01
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    \$\begingroup\$ It is a 741, it will always distort \$\endgroup\$
    – PlasmaHH
    May 28 '18 at 20:24
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The voltage gain of the circuit that you now show is 2. Total of feedback resistors divided by the input resistor equals the gain. Depending upon the amplitude of the input voltage this may not offer as much clipping as you would like. You could increase the gain to 10 (feedback = 470K) and realize quite a bit more clipping for a lower level input signal.

Note that you may want to steer away from the antique relic of the LM741. These do not operate very well unless the power supplies are +15V and -15V and the output will clip at levels about 2.5V below the +supply and 2.5V above the -supply. There are plenty of other much better opamps that can operate very well on a single voltage supply of 9V or even 5V.

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  • \$\begingroup\$ I think you nailed it Michael! In addition to probably needing some sort of capacitor on the output (for signal filtering?) The 10X gain makes more sense, as far as that seems closer to the actual values I might have used. Marking the answer as correct. Thanks for all your help. PS: Since you took the time to answer would you mind liking my post? Thanks. \$\endgroup\$ May 29 '18 at 13:03
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You example has a linear gain or -2 from Rf/Rin ratios if the source is low impedance and I concur is N.G.

For a bit more technical on simple distortion, read below from here with simple examples.

exerpt

Many audiophiles believe that 2nd harmonic is to be preferred over 3rd harmonic. Certainly it is simpler in character, and it is well agreed that orders higher than third are more audible and less musical. However when given a choice between the sound of an amplifier whose characteristic is dominantly 2nd harmonic versus 3rd harmonic, a good percentage of listeners choose the 3rd.

( but InterModulation (IM) distortion sounds nasty )

If you want to make a distorted note and draw it or choose different patterns and see the spectrum go here and choose [log Mag/phase view] and [sound] then drag freq slider.

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  • \$\begingroup\$ Thanks for the links Tony! That gives me something to look into further. \$\endgroup\$ May 29 '18 at 13:03
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    \$\begingroup\$ I once fixed a buddies stat-of-the art ( circa late '70's) bass synth that had a dozen special effects, flanger, fuzz bass, wah wah, etc in a tiny box of 2 dozen CMOS chips with part numbers erased because the designer made an error in level shifting 5V logic to bipolar supply CMOS analog switches that made it work marginally when new but fail soon after. Awesome sounds. Came from Silicon Valley used in Winnipeg. Guitarist is now famous in LA. It basically used digital time delay filters and mixers , VCF's with chopped analog. \$\endgroup\$ May 29 '18 at 15:12
  • \$\begingroup\$ But if want distortion, any simple underbiased common emitter high gain cct will fuzz up any sound. \$\endgroup\$ May 29 '18 at 15:18

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