I am trying to build a small desk-sized audio amplifier. I salvaged an old stereo cd player from the 90s and got an appropriate transformer (0-25V secondary) and an audio amplifier chip, the Sanyo LA4282 (Datasheet)
I have separated the block diagram in the attachment.
If you will notice, pins 1 and 6 are labeled "NF"
I am not sure what this means but they do allow one to connect to the feedback network - sort of. The problem is there is always the 300Ω input resistor in the way.
I would like to attach a feedback network for bass, midrange, and treble adjustments, such as a 3-band Baxandall equalizer network. (I read about it **broken link removed**), but any equalizer network will do. I have not researched them exhaustively yet.
The requirements of a passive Baxandall network are low source impedance and high load impedance - in the feedback loop, this seems perfect! The output of the power amp will be low impedance and the input should be high.
The problem is I am always going to connect my feedback network in parallel with the existing 30k/300 gain network, so I don't think it will work.
Would it be possible to do this or would I have to do my equalizing in a preamp stage?
EDIT - I am not looking for audiophile quality or I would have bought a better chip, the one I salvaged seems... merely okay. I may end up buying one anyway if I can't get the FB equalizer to work (one with a more easily accessed feedback network). If I do need to buy one I would appreciate suggestions for a 10W/ch stereo amp chip! I cant go much higher due to speaker and transformer limitations. I do not want it to sound like a 741 "project" audio amp though. Something at least halfway listenable.
I have separated the block diagram in the attachment.
If you will notice, pins 1 and 6 are labeled "NF"
I am not sure what this means but they do allow one to connect to the feedback network - sort of. The problem is there is always the 300Ω input resistor in the way.
I would like to attach a feedback network for bass, midrange, and treble adjustments, such as a 3-band Baxandall equalizer network. (I read about it **broken link removed**), but any equalizer network will do. I have not researched them exhaustively yet.
The requirements of a passive Baxandall network are low source impedance and high load impedance - in the feedback loop, this seems perfect! The output of the power amp will be low impedance and the input should be high.
The problem is I am always going to connect my feedback network in parallel with the existing 30k/300 gain network, so I don't think it will work.
Would it be possible to do this or would I have to do my equalizing in a preamp stage?
EDIT - I am not looking for audiophile quality or I would have bought a better chip, the one I salvaged seems... merely okay. I may end up buying one anyway if I can't get the FB equalizer to work (one with a more easily accessed feedback network). If I do need to buy one I would appreciate suggestions for a 10W/ch stereo amp chip! I cant go much higher due to speaker and transformer limitations. I do not want it to sound like a 741 "project" audio amp though. Something at least halfway listenable.
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