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x0x:vcfmods [2007/09/19 21:22] creekree deleted some BS |
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Perhaps this page could be split out into a grouping of pages soon. | Perhaps this page could be split out into a grouping of pages soon. | ||
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==== Filter Modulation (VCO) ==== | ==== Filter Modulation (VCO) ==== | ||
- | This is another relatively easy but awesome mod for the 303. Take the feed from the square wave (R36/Q8) and the saw wave (R105/Q28) and wire one to pin3 of an SPDT switch and the other to pin1 of the same switch. Use a SPDT switch so that you can select the saw or square wave as the modulation source. Connect pin2 from the switch to the 3rd leg of a 50K log pot. Wire the first leg of the pot to the junction of R71/Q9/Q11 (it is best to hook it up here instead of to ground so that it follows the same bias strategy as the env mod does - see page 8 in the 303 service manual: [[http://dl.analoghell.com/index.cfm?id=107]]). Hook up a 100K resistor to the center lug of the pot, the other end of the resistor goes to the junction of R71/R72/Q10-base, the summing point for the filter frequency control voltage input. | + | This is another relatively easy but awesome mod for the 303. Take the feed from the square wave (R36/Q8) and the saw wave (R105/Q28) and wire one to pin3 of an SPDT switch and the other to pin1 of the same switch. Use a SPDT switch so that you can select the saw or square wave as the modulation source. Connect pin2 from the switch to the 3rd leg of a 50K log [[http://example.com|External Link]]pot. Wire the first leg of the pot to the junction of R71/Q9/Q11 (it is best to hook it up here instead of to ground so that it follows the same bias strategy as the env mod does - see page 8 in the 303 service manual: [[http://dl.analoghell.com/index.cfm?id=107]]). Hook up a 100K resistor to the center lug of the pot, the other end of the resistor goes to the junction of R71/R72/Q10-base, the summing point for the filter frequency control voltage input. |
This will let you select the saw or the square as the modulation source independent of the what you have selected for the VCO. | This will let you select the saw or the square as the modulation source independent of the what you have selected for the VCO. | ||
Depending on where all the other controls are set you can get everything from an evil zipper to slowly dripping acid - among other things! | Depending on where all the other controls are set you can get everything from an evil zipper to slowly dripping acid - among other things! | ||
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{{x0x:fmmod_vco.png|}} | {{x0x:fmmod_vco.png|}} | ||
- | NOTE: the schematic above merely illustrates the text. There has been discussion on the forums lately that it would be a good idea to buffer the waveform output. | + | UPDATE: It is a good idea to buffer the waveform output. Use a 0.1uF ceramic cap after the 100K resistor. The Mod works great and is especially good at high resonance levels, so make sure you include the Resonance Boost Mod also! |
+ | UPDATE2 (by [[http://www.ladyada.net/forums/profile.php?mode=viewprofile&u=103|subatomic]]): that may be true (that 0.1uF being a good idea) however it doesn't sound as good... | ||
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If you don't particularly care about the numerology or DevilFish purity, you can simply play with various resistor values until you find a sound that works. Conversely, you could mount a potentiometer instead. | If you don't particularly care about the numerology or DevilFish purity, you can simply play with various resistor values until you find a sound that works. Conversely, you could mount a potentiometer instead. | ||
- | C17 might attenuate the signal too much, so you might need to replace it with a 10uF cap. | + | C17 might attenuate the signal too much, so you might need to replace it with |
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+ | a 10uF cap. | ||
=== A Devilfish Like Overdrive === | === A Devilfish Like Overdrive === | ||
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==== Resonance Warble ==== | ==== Resonance Warble ==== | ||
- | This is actually a PsMod, but it is included here for completeness sake. | + | This is actually part of the [[psmods# Power Supply Mods]]. However, it seems to be //not// working. |
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- | {{template>psmods#resonance_warble}} | + | |
==== Increased Filter Low End ==== | ==== Increased Filter Low End ==== | ||
According to RobbinWhittle, all you have to do is short out R47 (10K ohm resistor) by a length of insulated wire. Some other x0xers tried it out, and found that mounting a 4.7K ParallelResistor along with R47 works better (giving 3197 ohms resistance). This will also affect cutoff range to a degree. | According to RobbinWhittle, all you have to do is short out R47 (10K ohm resistor) by a length of insulated wire. Some other x0xers tried it out, and found that mounting a 4.7K ParallelResistor along with R47 works better (giving 3197 ohms resistance). This will also affect cutoff range to a degree. | ||
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{{x0x:reso_boost.png|}} | {{x0x:reso_boost.png|}} | ||
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+ | **Extra results:** | ||
+ | [[http://forums.ladyada.net/viewtopic.php?t=5215|Momerath says in this post]] "here are my suggestions for making a x0xb0x sound just like a 303" **r46 = jumper / r97 = 8.2k**. Presumably he added this as default (always on) on his box... Also he says "6.8k [for r97] was ridiculous if i recall". | ||
+ | [[http://forums.ladyada.net/viewtopic.php?t=5215&postdays=0&postorder=asc&start=15|charlie_says confirms it's good]] and says "you tend to get self resonance at the (very) top end but, I don't seem to have lost anything that I had before, and some combinations are definitely fuller. " and "but overall I think it's worth doing." | ||
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+ | [[http://www.ladyada.net/forums/profile.php?mode=viewprofile&u=103|Subatomic]] tried mome's mod, and found that it can be a bit whistly, but good, I went with a pot though so I could tweak. To explain Mome's use of shorting out r46... It's the | ||
+ | [[http://www.ladyada.net/wiki/x0x/envelopemods#increase_accent_range|"Resonance Increase Accent Range Mod"]] it seems to add more squelch on the accent, it's kinda subtle, but I could notice it most when the cutoff was way down it seemed to let through more resonant "scream" (sounds like "wow")... | ||
==== VCF External In ==== | ==== VCF External In ==== | ||
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For DevilFish like filter tracking, this is a little more complex, as we need to scale the voltages. This would probably mean using a pot as part of a voltage divider, and possibly multiplying the CV in before going through the divider. | For DevilFish like filter tracking, this is a little more complex, as we need to scale the voltages. This would probably mean using a pot as part of a voltage divider, and possibly multiplying the CV in before going through the divider. | ||
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+ | ==== increase resonance feedback ==== | ||
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+ | reported by bcbox [[http://forums.ladyada.net/viewtopic.php?t=5316|in this post]], the following is a cut-n-paste of his post. | ||
+ | <note warning> **VerifyMe:** Please remove this tag if you verify this mod works as described </note> | ||
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+ | you can increase resonance feedback by changing C21 and R122 | ||
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+ | Replace R122 with 68k | ||
+ | Replace C21 with .015uF | ||
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+ | this will increase resonance feedback while keeping the frequency response the same. The sound level will stay more constant as you increase resonance - not so much of a drop off. | ||
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