Hello everyone, I have an amplifier USBLASTER USB3003, I'll use it as a guinea pig to turn this into a full-range Class D.
The amplifier uses the original IRF640 MOSFET on the high side that is on the low side.
Using a driver card very similar to that of hollywood HXA3K.
My idea was to change the low-pass filter output, adapting frequency up to 20khz.
I already did some testing:
- I isolated the preamp section on board.
- I created a preamplifier built apart and I injected her audio signal directly into the amplifier driver board.
- I re-wound the inductor of the filter using the same enameled copper wire, changing the number of turns.
- I replaced the filter capacitors with a polyester specially calculated capacitor.
Everything else, for now remained unchanged.
Currently the amp sounds good in full range, but there is a serious problem:
the low-pass filter inductor becomes very hot after only 5 minutes of use at moderate volumes and more minutes pass more heats, to become really hot.
I noticed that the filter becomes hot even without audio signal.
I've never done such alteration of a Class D subwoofer, for this, I ask you, what else you would you change?
I have attached some pictures.
The amplifier uses the original IRF640 MOSFET on the high side that is on the low side.
Using a driver card very similar to that of hollywood HXA3K.
My idea was to change the low-pass filter output, adapting frequency up to 20khz.
I already did some testing:
- I isolated the preamp section on board.
- I created a preamplifier built apart and I injected her audio signal directly into the amplifier driver board.
- I re-wound the inductor of the filter using the same enameled copper wire, changing the number of turns.
- I replaced the filter capacitors with a polyester specially calculated capacitor.
Everything else, for now remained unchanged.
Currently the amp sounds good in full range, but there is a serious problem:
the low-pass filter inductor becomes very hot after only 5 minutes of use at moderate volumes and more minutes pass more heats, to become really hot.
I noticed that the filter becomes hot even without audio signal.
I've never done such alteration of a Class D subwoofer, for this, I ask you, what else you would you change?
I have attached some pictures.
Attachments
Do you even know the switching frequency of the circuit? It might not be suitable (high enough) for full-range use.
How can I measure the switching frequency? I have an oscilloscope.
Someone knows this driver card? You can change the switching frequency?
Someone knows this driver card? You can change the switching frequency?
wow!
Unfortunately, the driver board is covered with a black mastic material.
I would not know how to remove the material without the risk of breaking the Driver board.
I admit that I can remove that material, in your experience, you could change the switching frequency by varying some resistor or capacitor?
Unfortunately, the driver board is covered with a black mastic material.
I would not know how to remove the material without the risk of breaking the Driver board.
I admit that I can remove that material, in your experience, you could change the switching frequency by varying some resistor or capacitor?
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