Help designing a circuit - octave down guitar effects pedal

Thread Starter


Joined Nov 27, 2016
Hello. I am looking to build a guitar stompbox that will produce a deep bass-like sound. I have a number of components, mostly stripped from old electronics lying around my house, but due to the amount of money i have spent on recent purchases of soldering iron and pcb boards and various other tools and things, I have promised the wife i wont buy anymore components and will try to build from what ive got.
These include:
3 50k potentiometers
4k:2k input transformer
900:8 output transformer
2x 4560D dual op amp ic
2x 4558d dual op amp ic
An7112 amplifier ic
7476 dual jk flip flop
Npn & pnp transistors
Lots of diodes, resistors and capacitors
2 switches, one of which is built into one of the potentiometers
Input and output jacks
9v battery connector

Help would be appreciated. i have been trying to educate myself on how such a circuit will operate and will continue to do so.


Joined Dec 19, 2007
You're not going to achieve your goal with a random pile of electronic components.

You need to start with circuit schematic. Then see if you have any of the necessary components. Then start shelling out money for the rest. ;)

Google: octave down guitar effects pedal circuits



Joined Oct 2, 2009
A sophisticated technique would be to use a digital signal processor to digitize the input signal and measure the fundamental frequency. Then you can synthesize a new sound based on that frequency.That is how "chorus" can be generated, i.e. you can add the third and fifth notes to create a triad.

Thread Starter


Joined Nov 27, 2016
That circuit would not work. You have both /SET and /RESET tied to GND. The flip-flop will not toggle.
Also digital circuits will put out square waves which would be very harsh sounding.
I am aware of the nasty sounding harmonics associated with square waves, but still fancying this as a first pedal build. Thanks for your advice on the flipflops, i have a quad NAND chip and thought to implement them as a NOT between the j & k inputs. The logic tables ive attempted suggest the following circuit would work.



Joined Apr 11, 2010
Now however, you have left the S and R inputs floating. Not a good idea, as unpredictable results may occur. In order for the flip flop to operate, based on its JK inputs and a CLK signal, S and R must be high.