Hello,
Modified Karaoke microhone bass/treble input stage for removing microphonic effect on original PCB.
Issue was around Bass Treble and Echo mixer circuit. removed op-amp and related components for bass treble, replaced with circuit made on veroboard.
Schematic based on jrc4558 preamplifier circuit published in componentsinfo (Not posting URL)
opsting original schematic and modified one. (water mark is there in image).
Modified values (based on articles online) maked in red.
Tried both Inverting and on-inverting circuit, Inverting op-amp circuit has more distortion , hum noise when connected, this does not happen with Non-Inverted op-amp circuit.
Imput 1 and 2 is from another op-amp from microhphone UHF receiver circuit.
Modification removed microphonic effect.
Issue faced: when one of the mic (single mic) is used it works good, turned mic volume pot full, no distorsion.
Switched on scond mic, turn voume up, whem more than half way hum starts increases in volume by itself, when second mic volume turned down it goes off.
accidentally touched preamp resistor on pin 2 / 6 reduces this hum sound (there is other distorsion due to touching).
will it help if 33pf capacitor is connected in parrallel across 100K (feedback) ?
Requesting help to make circuit stable when using both mics.
Original Schematic:
Modified schematic:: Used RJC4580, two
Thank You
Modified Karaoke microhone bass/treble input stage for removing microphonic effect on original PCB.
Issue was around Bass Treble and Echo mixer circuit. removed op-amp and related components for bass treble, replaced with circuit made on veroboard.
Schematic based on jrc4558 preamplifier circuit published in componentsinfo (Not posting URL)
opsting original schematic and modified one. (water mark is there in image).
Modified values (based on articles online) maked in red.
Tried both Inverting and on-inverting circuit, Inverting op-amp circuit has more distortion , hum noise when connected, this does not happen with Non-Inverted op-amp circuit.
Imput 1 and 2 is from another op-amp from microhphone UHF receiver circuit.
Modification removed microphonic effect.
Issue faced: when one of the mic (single mic) is used it works good, turned mic volume pot full, no distorsion.
Switched on scond mic, turn voume up, whem more than half way hum starts increases in volume by itself, when second mic volume turned down it goes off.
accidentally touched preamp resistor on pin 2 / 6 reduces this hum sound (there is other distorsion due to touching).
will it help if 33pf capacitor is connected in parrallel across 100K (feedback) ?
Requesting help to make circuit stable when using both mics.
Original Schematic:
Modified schematic:: Used RJC4580, two
Thank You