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The title might be misleading/confusing. I'm building an amplifier with TDA2003 IC's which could be both suitable as a guitar amplifier and as a music amp. Where diodes come into this circuit? As you might know most transistor based amplifiers clip really harshly and it's amplifiers way of telling you "stop asking more from me!".
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The idea I have - putting soft clipping diodes (perhaps 1N4148?) before the input of the amp and to manipulate it in a way that it starts softly clipping just before the amp could say "little more and I will be angry".

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What's the point of that? You would start knowing when the amp starts to reach the peak of clean amplification and you would still get in comparison a nice more overdrive like tone rather than instant angry distortion. For me this is great as my amplifier is going to be used for both guitar and music so in (my) theory it should sound quite great both at low and high levels of amplification for both guitar and music!

Though I've came across a problem - how do you manipulate the diodes so they start clipping only at specific input level? Would it have to be resistors before diodes? And would this affect music audio listening quality when the signal is supposedly clean (and soft clipping diodes are on vacation until input is higher)__? P.S. perhaps you know any great diodes that clip softly besides popular 1N4148?

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  • \$\begingroup\$ That schematic is fairly meaningless, the input is connected directly to the output. There needs to at the very least be a series resistor in there somewhere. \$\endgroup\$
    – Andrew
    Nov 1, 2016 at 12:20
  • \$\begingroup\$ @Andrew Why is series resistor necessary? It's my first time working with overdrive schematics* so I could be called a newbie in this specific region \$\endgroup\$
    – Giedrius
    Nov 1, 2016 at 12:22
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    \$\begingroup\$ If the output is connected directly to the input then the output is always going to be exactly the same as the input, the diodes will have no effect. In reality they will have some sort of effect, when the input voltage tries to go over about 1.4 volts the diodes will be fully on and clamp it. What happens then depends upon the input source, it may limit nicely, it may be unable to cope with the load and burn out or it may supply enough current to blow the diodes. Either way a circuit that depends on the input source being non-ideal to work isn't a good plan. \$\endgroup\$
    – Andrew
    Nov 1, 2016 at 12:30
  • \$\begingroup\$ Changed schematic to one which seems more promising \$\endgroup\$
    – Giedrius
    Nov 1, 2016 at 13:09
  • \$\begingroup\$ Germanium diodes are softer .I use them for one off jobs .They sound really good and look good on the scope but not so good for volume production runs . \$\endgroup\$
    – Autistic
    Nov 18, 2018 at 3:24

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That new schematic works fairly nicely. You should be able to click on the circuit below and simulate it. You end up with the output being clipped but with nicely curved corners rather than hard stops at the top and bottom.

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ If the "clipping" (better: limiting) is not "soft enough" you can place a suitable resistor in parallel to the diodes. \$\endgroup\$
    – LvW
    Nov 1, 2016 at 14:28

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