Differences

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--- mbhp_genesis [2016/05/15 15:09] – [Summary] sauraen
+++ mbhp_genesis [2023/09/05 04:19] (current) – [Component stuff chart] sauraen
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-{{http://midibox.org/forums/uploads/monthly_2015_11/large.mbhp_genesis_1e_front.jpg.97a341757653897ba6218555ea690650.jpg?640}}
+{{http://midibox.org/forums/uploads/monthly_2015_11/large.mbhp_genesis_1e_front.jpg.54c08f42d0fd242b1039f5e83a067ddd.jpg?640}}
 ====== Summary ======
@@ Line 82: / Line 82: @@
 | 3   | --    | OPN2 Left channel summing node |
+This means that if you're using two or more boards, stuff everything up to J7 on all boards, and connect each pin of J7 across all boards. Then, only stuff the parts downstream of J7 on one of the boards, and take the audio output from J8 on that board. (This is assuming you want everything mixed into one stereo pair.)
 ==== R18, R19, R20 ====
 These are three-pin headers to connect potentiometers to adjust the relative volume (and panning if desired) of the OPN2 and PSG. As is obvious from the schematic, R18 is for OPN2 Left, R19 is for OPN2 Right, and R20 is for PSG. The potentiometer is 10k nominal (will work fine with 5k or 2k), audio type (A) preferred but not required. It is intended that a dual-gang potentiometer would be used to adjust the OPN2 levels together, and a separate single one for the PSG. If panning is desired, after the level potentiometers, connect a 20k or 50k potentiometer between the Left output and Right output (R18:2 and R19:2) with its wiper connected to +2.5V (R18:1).
@@ Line 140: / Line 141: @@
 | 1 | Y2 or Y4 | 3.58 MHz (or 4 MHz) oscillator | 520-TCH357-X | Oscillator (either half-size/8-DIP or 5x7mm SMD) at desired PSG frequency. MIDIbox Genesis firmware will correct frequencies to match original VGM pitch. |
 | 3 | Q1, Q2, Q3 | 2N7000 or BS170 | 821-TSM2N7000KC821-T or 512-BS170 | Any small-signal N-channel MOSFET with the gate as the center pin; the board silkscreen is for 2N7000, if you use BS170 (as I did) mount them backwards to match the source and drain pins. |
-| - | J1, J2, J5, J6, J7, J8 | 0.1" pin headers | Buy in bulk | Headers; J1, J2, and J7 connect all boards together, so put sockets on one side of the boards and have the pins sticking through on the other sides. J5 and J6 are individual on each board if used, and J8 is only on the final board. |
+| - | J1, J2, J7, J10 | 0.1" stackable pin socket/headers | 782-A000086 | Pin sockets with long pins (from Arduino shields), for stacking the boards together. Buy in bulk and combine them for the appropriate sizes. Use a regular pin header for the lowest board in the stack; have each header mounted with the socket below the board and the pins sticking out the top. See [[http://midibox.org/forums/uploads/monthly_2017_08/large.finished_inside2.jpg.459682a854f131f34f39a57ba6cdb27a.jpg|this photo]] of the stack. |
-| - | J10 | 0.1" dual row pin headers | Buy in bulk | Headers; J10 connects all boards together, so put sockets on one side of the boards and have the pins sticking through on the other sides. |
+| - | J5, J6, J8 | 0.1" pin headers | Buy in bulk | Headers; J5 and J6 are individual on each board if used, and J8 is only on the final board. |
 | 1 | L1 | 10 uH inductor | 434-SMCCN-100K-02 | For LC filter for analog power rail |
 | 2 | C12, C13 | 100 uF electrolytic | Buy in bulk | Power rail filter caps |
@@ Line 173: / Line 174: @@
 The values I used for my quad builds are on the schematic and in the parts list. The normal values are for use with YM2612s, and the values in parentheses are the ones to use with YM3438s. All other parts which just show one value are the same on both builds.
 ===== Component stuff chart =====
-Here is a chart of what components should be stuffed on each build configuration I could think of. In most cases, several of these build configurations will be active at the same time (e.g. in a typical four-board setup, the top board is A, B or C, D, (E), F, G, H, I, M).
+Here is a chart of what components should be stuffed on each build configuration I could think of. In most cases, several of these build configurations will be active at the same time (e.g. in a typical four-board setup, the top board is A, B or C, D, (E), F, G, H, I, M. Note that MIDIbox Quad Genesis requires F, G, H, I).
 ^ Label ^ Description ^
@@ Line 196: / Line 197: @@
 ^ Parts ^ A ^ B ^ C ^ D ^ E ^ F ^ G ^ H ^ I ^ J ^ K ^ L ^ M ^ N ^ O ^ P ^
-| U1, C1, C14, C15, Y1 or Y3, C20, C21, R11, R12, R15, R16, C23, C24, R18, R19, R21, R22 | X |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
+| U1, C1, C14, C15, Y1 or Y3, C20, C21, R11, R12  | X |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
 | R8, R9 |   | X |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
 | R33, R34 |   |   | X |   |   |   |   |   |   |   |   |   |   |   |   |   |
-| U2, C2, Y2 or Y4, U10, C10, Q2, Q3, R4:6, R10, C22, R13, R14, R17, C25, R20, R23, R24 |   |   |   | X |   |   |   |   |   |   |   |   |   |   |   |   |
+| U2, C2, Y2 or Y4, U10, C10, Q2, Q3, R4:6, R10, C22, R13 |   |   |   | X |   |   |   |   |   |   |   |   |   |   |   |   |
-| J1, C12, L1, C13, C11, U4, C4, C16, R31, R32, C18, C19, U5, C5, C17, R25, R26, C29, C30, C31, C32, R27:30, J8 |   |   | X | X |   |   |   |   |   |   |   |   |   |   |   |   |
+| J1, C12, L1, C13, C11 | X |   |   | X |   |   |   |   |   |   |   |   |   |   |   |   |
 | J6, R7 |   |   |   |   | X |   |   |   |   |   |   |   |   |   |   |   |
 | U7, C7 |   |   |   |   |   | X | X |   |   |   |   |   |   |   |   |   |
 | U8, C8 |   |   |   |   |   | X | X | X |   |   |   |   |   |   |   |   |
 | U6, C6, Q1, R1 |   |   |   |   |   |   | X |   |   |   |   |   |   |   |   |   |
-| U9, C9, C26:28 |   |   |   |   |   |   |   | X |   |   |   |   |   |   |   |   |
+| U9, C9 |   |   |   |   |   |   |   | X |   |   |   |   |   |   |   |   |
 | J5 |   |   |   |   |   |   |   |   | X |   |   |   |   |   |   |   |
 | Short U3:5 to U3:15 |   |   |   |   |   |   |   |   |   | X |   |   |   |   |   |   |
@@ Line 211: / Line 212: @@
 | Short U8:3 to U8:6  |   |   |   |   |   |   |   |   |   |   | X | X |   |   |   |   |
 | U3, C3, J2 |   |   |   |   |   |   |   |   |   |   |   | X | X |   |   |   |
+| U4, C4, U5, C5, C16:19, C23:32, R15:32, J8  |   |   |   |   |   |   |   |   |   | X | X | X | X |   |   |   |
 | Short U3:13 to J3:2, short U3:12 to J3:1 |   |   |   |   |   |   |   |   |   |   |   |   |   | X |   |   |
 | Short U3:11 to J3:2, short U3:10 to J3:1 |   |   |   |   |   |   |   |   |   |   |   |   |   |   | X |   |
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 For the OPN2 chips, the YM3438 is a complete reimplementation of the YM2612 in CMOS instead of NMOS. They also changed the output stage to get rid of some analog error in the YM2612's DAC, which produces a distinctive "ladder effect" sound in the audio output, as well as making the output about 10-20dB louder (which also produces excellent signal-to-noise performance). FM synthesis purists might be inclined to choose the YM3438; retro gaming fans will probably go with the YM2612, as this is the physical chip used in the Mega Drive / Genesis Model 1.
+(Note about the next two paragraphs: the resistor values given in the parts list are the ones I used and tested for each of YM2612 and YM3438, there's no clipping or other issues. If you don't want to experiment, use those.)
 The differences for this module are relatively simple. For a YM2612, the audio outputs require a known load to perform to spec--these are R8 and R9. The value of 2.2k was taken from the [[http://www.sega-16.com/forum/showthread.php?26568-Introducing-the-Mega-Amp-The-universal-Genesis-audio-circuit|Mega Amp design]], but some experimentation may be warranted.
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 ===== Notes about the YM2612's Test pin =====
 From [[http://gendev.spritesmind.net/forum/viewtopic.php?t=386|reading photomicrographs of the YM2612 die and further related hacking work]], it has been confirmed that this is an I/O pin, not just an output. Hence the MBHP_Genesis module contains circuitry to both read and write the pin on each YM2612 independently, as well as to select the pin direction. If the pin is mistakenly configured as an input (so the module drives it) while the YM2612 is also driving it, a protection resistor R2 allows the YM2612 to override the state of the line without damage to either device.
+When appropriately configured as such via bits in the test registers discovered by Sauraen, the Test pin outputs a SYNC signal--a pulse for one of the 24 operators in the cycle. Using this pulse to know when to start and putting the OPN2 in a particular test mode, MIDIbox Quad Genesis periodically reads out the state of all 24 operators, and measures the average volume of the operator for the VU meter display on the front panel.