4093 quad oscillator project - question

[spectreman]

hello all,

i'm building a quad-oscillator pedal/synth as shown here:

http://getlofi.com/shop/4093-quad-oscillator-kit/

my question is, what value capacitors can i swap into the design to get the lowest possible frequencies?

i'm new to this stuff, so i'm unsure which capacitors in the initial design to keep, and which ones to swap out and play around with for low tones...

here is what comes with the kit:

2 x 1uF Capacitor
1 x 47uF Capacitor
2 x 10uF Capacitor



if you have any suggestions, let me know!

thanks!

[slacker]

Hi

It's hard to say just from the PCB but I would guess the 1uF and 10uF caps are the oscillator caps, the 47uF looks like it is connected to the power input so it is probably power supply filtering.
With 100k pots and 1uF or 10uF caps it should already go way below audio frequencies but if you want to change them basically however much bigger you make the caps that's how much slower it will go. Making the caps bigger will also make the fastest speed slower, so you might need to make the resistors smaller if you want to keep the same range of frequencies. You can also make it go slower by making the pots bigger, swapping them to 1Meg pots would make it 10 times slower.

Welcome aboard

[spectreman]

yeah!  thanks, that's what i wanted.  i'm going to try the 1M pot swap.

a few questions - (the kit comes with (4) Reverse Log Pots...)

i can use 1M single linear taper rotary pots for the swap right?  i'm guessing they will work backwards from the reverse log pots...correct?

OR do i need to use logarithmic taper pots as opposed to linear taper...

[nocentelli]

Look up reverse log pots - they are used for time constant controls (e.g. speed/rate pots in tremolo, phaser or flanger circuits) because they move quickly through the slower speeds, but the change is slower as you reach higher speeds: this makes it easier to dial in the speed you want.

Getlofi don't provide a schematic, but from the demo's I assume it is like the schem below with each oscillator output feeding into the next: this gives much more complex patterns than four discrete oscillators being mixed at the output would, but also means it will be harder to dial in a low frequency drone, since the output is four oscillators running series with each being modulated by the one/two/three that come before it.

https://andreassiagian.files.wordpress.com/2013/02/quad-oscillator-4093-schematic2.png

[spectreman]

OK - so i decided to go with a rotary switch and add a series of different value capacitors for different tones.  a few questions since i'm new to this:

1.  do i just use a single pole 12 position switch?
2.  what capacitor position on the board do i connect the switch to?  (there are 5 unique cap positions on the board)
3.  any suggestions on a range of capacitor values?
4.  do i need to mess with resistor values when i do this?

thanks for any help.  i'm sure this is all common knowledge to most of you, but any help from you helps me understand how this all works.

thanks!