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Power Supply Mods

On / Off Switch

Basically Trivial. Locate the power jack. On the solder side of the I/O-board, cut the trace that almost circles the jack between the first two solder pads. Refer to this picture. Solder the wires leading to your switch as shown here. Find a good place on your I/o panel to mount the switch. Before drilling your precious panel make sure the switch doesnt stick out too much or the 2200uf caps on the I/O-board might get in the way!


You could use 2 9 Volt batteries after the regulator to power the x0xb0x. From 'guest' on the forums:

Of you dont care too much about power efficiency the simplest thing to do would be to put two 9v cells in series run the opamp off of the 18v and the 5v and 6v regulators off the first 9v. The bottom 9v will run out faster than the top one but you could just reverse them when this happens this will probably give you 6hours of life max though.

By performing the kill_switch_on_headphone_amplifier Mod, you could conserve some more battery power, as the 6V power won't be drawn (very much) unless you plug the headphones in.

Resonance Warble

The original TB303 had a sketchier power supply then the x0xb0x. From TheGerman:

"the warble in the resonance is due to powerline fluctuations since the synth is run off of an op amp as a power supply. it has troubles at high current draw. also there are tons of low pass filters on the supply that cause droops when large power surges occur. r95 and c28 for example. at any rate, the power supply we built was a bit stiffer than the original. this stiffness can be taken away by increasing the resistance of 100ohm resistor that feeds the opamp. i havent verified this but im pretty sure it would give more warble as the op amp would saturate sooner at higher currents also the bypass cap at that point could be decreased"

A 200 or 220 ohm resistor at R1 apparently does the trick, though you could go as high as 270. Another option is to attach a pot, so you could dial in the crappiness.

NOTE REGARDING THIS MOD: Thus far, there seems to be only one confirmation by a x0xb0x user that this mod works, and this user had another person build his kit. The overwhelming impression one gets from Ladyada's forum is that this mod does not work…at least at the values suggested above. Verification of this mod would be greatly appreciated.

A counter-NOTE: guest mentioned he did this mod, and other people have reported bad PSUs causing warble in the resonance when the res was turned up high. A good question would be what resistor value causes the warble. perhaps do a test with a 5k pot, and play around…

/home/ladyada/public_html/wiki/data/pages/x0x/psmods.txt · Last modified: 2016/01/28 18:05 (external edit)