i found this schematic for the stupid box:
(http://i8.photobucket.com/albums/a13/vigorandkandor/stupibix.jpg)
i know pin 1= output
pin 2 = -
pin3 = +
do i need to use any other pins of this op-amp (tl072) to make it work?
You don't need to use the remaining pins, you can just tie them to ground if you want. I'd personally use the other half of the opamp to make a second Stupid box which you can switch between. Perhaps make one with Ge diodes or one with with four diodes (two sets of two in series) for less clipping.
so pin 8 doesnt need +V for the op amp to work?
pin 8= Vcc
and pin 4= Vee
i made this pedal, actually first pedal i have tried to make from scratch. i noticed in other schematic's with simalar op-amps the Vcc gets positive voltage, and the Vee is connected to ground. i bread boarded this schematic and my signal doesnt get past the op-amp. i just wanted to make sure that the op-amp is getting all the power needed.
Yeah, pin 8 definitely needs to go to the +'ve power supply (usually +9v), and pin 4 will need to be grounded for anything to work.
You can't run a car without petrol, you can't run an op-amp without power!
just to be sure, if i just connect +V (9v) to pin 8 and pin 4 to ground it should work.
thats what i thought. thanks for your help.
yeah it did work! awesome. thanks for the help. sorry for being a noob kinda. all i have done in the past is mod circuits.
i thinking i might use the other half of the chip for a Microamp type boost circuit. hmmm....
Hey no problems, everyone has to start somewhere! Glad you got it going.
Like I said earlier, i'd definitely consider building a copy of the circuit using the un-used portion of op-amp. If you use the same diodes as the first, but put a pair of Ge diodes in series with them you'll have softer clipping around 0.5v higher (most common Ge diodes turn on at 500mV, I use OA90 & OA91's) than the first that will give you more boost and slightly less distortion.
If you don't use the second half of the opamp, ground pin 5 and tie pins 6 and 7 together.
i added an LED in series with one of the existing diode, and i really like what it did.
when i get an enclosure bigger than the MXR sized ones i will see about using the second half of the opamp. when i tested the circuit i used a carbon battery and it sounded fuzzy and good, when i use a power supply it doesnt sound as fuzzy anymore. could the battery really have that much of an affect on the circuit. i didnt leave any room for a bettery inside. if it turns out it does makes a difference than i guess i have to move some stuff around.
It's possible that effect could have been caused by low voltage lowering the clipping threshold, or conversely a high voltage from a fresh carbon battery, who knows! Carbon batteries especially have quite significant internal resistance, so perhaps that adds some 'sag' maybe?
I was wondering if you could record some sound samples of this thing at clean, low and medium gain for me? I've just done a layout for Tim's Q&D VCF and i've got a half op-amp spare, I was thinking of putting this in front to add some harmonic interest.
i have played around with the diodes quite a bit in this little thing. even without diodes it will drive quite a bit. i didnt build this pedal thinkning i would love it as much as i do! it has an overdrive feel, with a hint of fuzz on top. after all is said and done i like mine with the LED in series with one of the existing diodes. i will try to get some clips recorded maybe today. if i do record it will be on a clean solid state amp, so the pedal will be doing all of the driving. the only other thing i did was i used a .15uf cap for the input.
if you go to www.subdecay.com (http://www.subdecay.com) you can hear some clips of the circuit. click on the Stupid Box link.