opl3_module_modified
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opl3_module_modified [2014/01/28 09:02] eptheca |
opl3_module_modified [2014/01/28 11:05] eptheca |
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| - | == MBHP_OPL3 modifications == | + | ====== MBHP_OPL3 module modifications, the 5V option ====== |
| + | The [[http://www.ucapps.de/mbhp_opl3.html|MBHP_OPL3]] module originally has three TL074 op-amps, and a circuit that needs +/-12V bipolar power supply. | ||
| + | In Wilba and nILS [[sammichfm|sammichFM]], they use two OPA4348 rail-to-rail op-amps, that can be powered by 5V. | ||
| + | |||
| + | Sauraen suggested another 5V rail-to rail op-amp, the MCP6004, which is pin compatible with the TL074, and a way to modify the OPL3 module to use these.[[http://midibox.org/forums/topic/18492-mbfm-5v-option/]] | ||
| + | |||
| + | - Replace R5,R7,R10 and R13 with jumpers\\ | ||
| + | - Bridge IC6 pads 1&3, 5&7, 8&10 and 12&14\\ | ||
| + | - Leave out:\\ | ||
| + | IC6\\ | ||
| + | R4, R6, R8, R9, R11, R12, R14, R15\\ | ||
| + | C15, C16, C19, C20, C23-C30\\ | ||
| + | - Bridge C20 pads (to supply Ground for the op-amps)\\ | ||
| + | - Leave out bridges to IC6\\ | ||
| + | - Use MCP6004 for IC3 and IC5\\ | ||
| + | - Supply 5V to the +12V pin, and Ground to Ground\\ | ||
| + | |||
| + | This way the second buffering stage is left out. | ||
| + | |||
| + | In the sammichFM, nILS designed a separate dedicated 5V supply for the DACs (YAC512) and the op-amps.\\ | ||
| + | To modify the OPL3 module for this approach:\\ | ||
| + | |||
| + | - Cut the trace between the 5V pin of the Oscillator and the DAC\\ | ||
| + | - Leave out the middle horizontal bridge from IC1\\ | ||
| + | - Connect the right pad of this bridge to the 5V pin in the middle of the board with a jumper\\ | ||
| + | - Connect the left pad of this bridge to the 5V pin of the Oscillator with a jumper\\ | ||
| + | - Two separate 5V voltage regulators, IN pins connected through a ferrite bead\\ | ||
| + | - One 5V source to Core and J1 of OPL3 module\\ | ||
| + | - The other 5V source to J3 of OPL3 module\\ | ||
| + | - Ground ONLY to J3!\\ | ||
| + | |||
| + | Tips:\\ | ||
| + | - Starlike wiring (Ground from PSU to each module + Audio outputs)\\ | ||
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| + | |||
| + | I can vouch for these mods :)\\ | ||
| + | My MIDIbox FM V1 has hardly any noise, and it has enough gain. | ||
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| + | {{:opl3.jpg?direct|}} | ||
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opl3_module_modified.txt ยท Last modified: 2014/01/28 11:40 by eptheca
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