Differences

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--- opl3_module_modified [2014/01/28 09:02] – eptheca
+++ opl3_module_modified [2014/01/28 11:40] (current) – eptheca
@@ Line 1: / Line 1: @@
-== 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 (IC3 The op-amp, not the DAC, labeling error)\\
+- 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)\\
+I can vouch for these mods :)\\
+My MIDIbox FM V1 has hardly any noise, and it has enough gain.
+{{:opl3.jpg?direct|}}