Id like to use a soft clipping circuit on a Lm3886 used for musical instruments. Ive seen some basics shown on various websites using diodes in the NF loop and also on the outputs, but most appear to be for distortion and are used at the preamp level. Can this be done simply for a LMxxxx?
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Clip At Input
This is my untested opinion and others will need to confirm/deny. The
LM3886 could go unstable if the clip diodes are placed in the op-amp's
feedback path. Put a 50k trimpot at the LM3886's input. Put a pair
of 1N4148 diodes, parallel in opposite directions, across lo-to-hi on
the pot. Send the wiper output of the pot to the input of the LM3886.
Place a 10K resistor in series with the pot/diode combination's hi side.
Drive the pot/diodes network from the free side of the 10K resistor.
The diodes will clip the input, softly, at about 2V p/p. It has to be
overdriven by almost 20db (about 7V RMS) to completely change a
sinewave into a square wave. Set the pot by applying a few volts
RMS to the free side of the 10K resistor and adjust the pot for an
output level lower than the natural output clipping voltage of the
LM3886. Instantaneous peaks should be clipped inaudibly and hard
overdrive should no longer stress the LM3886.
This is my untested opinion and others will need to confirm/deny. The
LM3886 could go unstable if the clip diodes are placed in the op-amp's
feedback path. Put a 50k trimpot at the LM3886's input. Put a pair
of 1N4148 diodes, parallel in opposite directions, across lo-to-hi on
the pot. Send the wiper output of the pot to the input of the LM3886.
Place a 10K resistor in series with the pot/diode combination's hi side.
Drive the pot/diodes network from the free side of the 10K resistor.
The diodes will clip the input, softly, at about 2V p/p. It has to be
overdriven by almost 20db (about 7V RMS) to completely change a
sinewave into a square wave. Set the pot by applying a few volts
RMS to the free side of the 10K resistor and adjust the pot for an
output level lower than the natural output clipping voltage of the
LM3886. Instantaneous peaks should be clipped inaudibly and hard
overdrive should no longer stress the LM3886.
I don"t think putting Clipping diodes on the LM3886 would work the way you want .....
Most Diodes have a Clipping threshold of 0.7v so the output voltage of the Chip will be at 0.7v (everything above that will be clipped) so you couldn"t get hardly any volume out of the Chip , you might even fry the Diode .....
If you want to add diode clipping put a regular opamp stage with diode clipping before the LM3886 ......
Cheers
Most Diodes have a Clipping threshold of 0.7v so the output voltage of the Chip will be at 0.7v (everything above that will be clipped) so you couldn"t get hardly any volume out of the Chip , you might even fry the Diode .....
If you want to add diode clipping put a regular opamp stage with diode clipping before the LM3886 ......
Cheers
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