subatomic x0xb0x mod guide...
I created this guide to mod my x0xb0x as shown above, it's mostly cut-n-paste from the x0xd0x wiki, with several annotations, parts lists, wiring diagrams, and other clarifications made by myself...
Feel free to integrate any of this info back up to the x0xd0x wiki.
The mods were selected for 1.) simplicity 2.) dramatic effect 3.) ability to turn off and return the x0xb0x back to stock (most important to me was to not lose the x0xb0x sound!). Total cost of parts are around $20-$30, and for this small amount, we get some nice additions to our x0xb0x arsenal, check out the sound clips
While modding my box, I took pictures, which you will find below at the appropriate places
Sound Clips (with mostly qualitative descriptions...):
As you can see, many of the effects are subtle, they're still x0xb0x, but twisted
Table of ContentsCosmetic:
Using these links, search on the catalog page for the 12pin ones, get the right-angle kind for the main board so your case closes tight (I found out after I soldered mine, so I had to trim some plastic off the connector to make it have enough clearance...) maybe order both kinds (straight and right angle) just in case...
Molex connectors at Futurlec:
See my Tutorial on making cables
Many light coats to prevent running (around 6-9).
Labels for the x0xb0x.at 300dpi...
Layout for the mods.
Layout for the labels.
switch pinL1 - .1uF switch pinL2 - .1uF switch pinR1 - .01uF switch pinR2 - .01uF switch pinC1 - C21 (pin1) switch pinC2 - C20 (pin1) .1uF - C21 (pin2) .01uF - C21 (pin2) .1uF - C20 (pin2) .01uF - C20 (pin2)
Remove R61 and replace it with a jumper wire. This will make it possible to turn the envelope modulation all the way down. If you want to make it switchable, leave R61 in place and solder a wire from each terminal of R61 to a switch. This will enable you to shorten out R61, much like replacing it with a jumper wire. Increasing the range by 3 times
Add a 100K resistor in parallel with R63. Easy. [This basically reduces the resistance to ~68.75K, 1/3 the original value.] Parts List
envmod all the way down:
hook this switch to R61 - center post of spdt switch to one side of R61 - "on" post of spdt switch to other side of R61
hook this switch to R63 (with a 100k in line) - center post of spdt switch to 100k, then to one side of R63 - "on" post of spdt switch to the other side of R63
The plan is to replace R97 only, controlled by a single "boost" pot:
Resonance boost switch to enable/disable, you could replace the 5k + 5.6k section by any value...
______ v | SPDT /o--/\/\-- o--/\/\--o .-----/ 5k 5.6k |--o | o--/\/\--------------o R97 | 10k '--------------------------------o
SPST switch puts 12V onto D36/R134 when on: D36 R134 R136 --->|--o---/\/\/--o --/\/\/--o---|> 12V | | | | o o | \ | \ | | SPST on/off | | | o----------------------+
Replace the r123 1.5M resistor with 1M pot in series with 500k resistor (or ideally use a 2M pot and no resistor): Parts List
Notes: the decay is loooong. you'd probably be fine using 1Mpot directly (and possibly add in a small value in series). I doubt you'd miss the long falloff of 1.5M... just an idea.
http://dl.analoghell.com/index.cfm?id=107). From the middle leg of the pot hook up a 100k resistor. Wire the other end of the resistor to the junction of R71/R72/Q10-base, the summing point for the filter frequency input. This will let you select the saw or the square as the modulation source independant 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! Parts List
SPDT pin1 - R36/Q8 - square wave source SPDT pin3 - R105/Q28 - saw wave source 50k pot pin3 - SPDT pin2 - selected wave form... 50k pot pin1 - R71/Q9/Q11 - reference voltage 50k pot pin2 - 100k res - R71/R72/Q10-base - summing point for filter frequency input
SPDT /-o1 SQR R36/Q8 (waveform switch) 2o--/ | o3 SAW R105/Q28 (waveform switch) | o 3 | / 50k \<-o-----/\/\/---------o R63/R72/Q10/R71 (summing point, filter input) pot / 2 100k \ | / R71 o 1 \ '----------------------o Q11/Q9/R71
Notes: the latest x0xd0x wiki calls for a 100nF cap in series with the 100k. I tried this and the effect was much more quiet (undesirably so). I'm guessing the 100nF cap is to buffer the signal... The mod works better without the 100nF.
100k pot pin3 - C38 (VCA output) 100k pot pin1 - GND (no sound) 100k pot pin2 - 100nF - 20k - R71/R72/R63 (summing point for filter frequency input)
C38(-) (VCA output) o 3| / 100nF 20K 100kA \<-o-||---\/\/\/--- to R72/R71/R63 (summing point for filter frequency input) pot / 2 1| o GND (no sound)
Notes(1): get GND from one of the VRx pots on the mainboard... connect to the pot's case pin. These all seem to be grounded, but check to be sure in case future revisions of the mainboard change.
Notes(2): 100nF was 47nF on jonnay's wiki, wonder why this changed? I tried both 47nF and 100nF and couldn't tell a difference (I recorded both signals and A/B'd them to be sure).
Notes(3): also this text was deleted from the above paragraph... I found with this mod you get the full modulation with the pot at max when using about a 62K resistor back to the summing point of R71/R72/R63(as opposed to 100K). strange... I did not try 62k, i'm assuming the cap is to buffer the signal.
You could get a devilfish like overdrive if you remove R62,and put a 3.3K Ohm resistor in series with a 250K Ohm Pot.
wire this in place of R62: o 3 R62 / SW1 pin2 2 \ (in) From Switch ----o->/ 250k \ C17(+) / R62 1 o-----/\/\/\----- (out) 3.3k of course, that's a little inexact... we'd rather go exactly from 220k (overdrive off) to 3.3k (devilfish mystical number) o 3 R62 / SW1 pin2 2 \ (in) From Switch ----o---->/ 233k (actual value of my 250k pot) | \ o/\/\/o-----------/\/\/\----- (out) 3M 1 3.3k C17(+) / R62 (in parallel makes it a 216k pot)
---------- Parts List
simple option (won't turn all the way off):
Connect in place of R62 resistor. 3 o---- 5.333V (R101 or R36/J4 pin1) / 2 \ 500kA R62/waveformswitch pin2-o-->/ \ 3.3K 1 o-----/\/\/\----- output to C17(+)/R62Parts List
100kA pin1 - R101 or R36/J4 pin1 (5.33V reference) 100kA pin2 - R62/waveform switch pin2 (waveform pin2) 100kA pin3 - 3.3k resistor - R62/C17(+) (output)
"I found an intesting fact recently while continuing the design of a custom 303 mod. The output from the VCO is not buffered. In the stock 303 this is not a problem because the signal is just attenuated and then ac-coupled to the input of the VCF. However, if you add a level control that references to the 5.333v bias voltage of the 303 - such as you would if you were adding a level control - there is a load effect on the VCO signal if it is not buffered first. The result is that the character of the square wave changes quite significantly. It looks sublt on a scope but it is very audible. So you're better off not referencing your overdrive pot to the 5.333v bias point. I know that the devilfish doesn't buffer the output of the VCO so it would be interesting to compare the square wave coming from a devilfish with the overdrive/level control in place versus with it bypassed." http://www.ladyada.net/wiki/x0x/vcfmods#filter_overdrive . "The best thing to do is not to use a voltage divider but rather just current limit the signal into the VCF, simply use a 250k pot in series with a 3.3k resistor both in place of R62. This won’t allow you turn turn the VCO signal all the way off (short of adding a switch) but it’s not important for most people anyway"
Notes: only difference from the "devilfishlike overdrive" is the bigger 500k pot and connection of 5.333v to the pot's pin3.
Notes(2): I didn't like how this mod sounded. 1.) sound coloration 2.) even at "silence", I could still hear audible clicks. Because of this, the mod wasn't useful to me.
Notes(3): I reverted this change in favor of the "devilfishlike overdrive" current limiter version that preserves the default x0xb0x sound. I do not recommend using 5.33V here, unless you really need the silence (and don't mind some clicks instead of silence), or really want devilfish purity.
Notes(4): I didn't use a log pot, and it sounds fine.
From C38 ----+---- To VR8 | / SPDT on-off-on (intensity selection, low/off/high) o o ~ ~ ~ | | ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o o | +--+ | +--+--+ | | | V V - Diodes - - ^ | | | --- --- --- GND GND GND Here's a version with diode type selection: From C38 ----o---- To VR8 | / SPDT on-on (diode type select, germanium/silicon) (germanium) o o (silicon) ~ ~ ~ ~ | | ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o o | | DPDT on-off-on (distortion intensity, low/off/high) / / o o o o--------------------+ ~ ~ ~ | | +--------------------. | ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ (low) o o (high) (low) o o (high) | | | | | +-----+ | +-----+ | | | | | | V V - Germanium V V - Silicon Diodes - - ^ Diodes - - ^ | | | | | | --- --- --- --- --- --- GND GND GND GND GND GNDChoosing Diodes From the Guitar Effects FAQ: Silicon is reputed to clip abruptly, causing a harsh sound. Germanium clips at about half the voltage of a silicon diode, but is reputed to turn on more slowly in its smaller range. LEDs turn on at about two silicon diode drops, and are also reputed to be slower turn on, with it and germanium giving more “tube like” sounds. Some units with “tube” in the title use LEDs or germanium for clipping. Oddly enough, the Marshall JCM800 uses a set of two pairs of silicon diodes back to back as clippers. This seems strange in a Marshall, but it is there. When I looked at the schematic, I first thought it was a protective clamp for a tube grid, but the circuit doesn’t work that way. They are there for the distortion. Parts List
VR8/C38 - SPDT input pin2 SPDT pin1 - DPDT input 1 SPDT pin3 - DPDT input 3 DPDT pin1a - 1 LED in DPDT pin1b - 1 germainium in DPDT pin3a - 2 LEDs in DPDT pin3b - 2 germainiums in LED/Germainium outputs - ground (VR8 body)
Notes: this mod seems to be a suggestion, not an authentic devilfish mod