my apologies for straying off the Arduino reservation, but this is on-topic of "General Electronics", so i hope you guys don't mind.
i have been dabbling a bit with circuits sans micro-controller and marvelling at what is already possible with simple electronic basic circuits (my topic on low-pass filters last week was my first !)
playing with a 555 timer chip was simple enough and the square wave generator was well comprehended, along with trying various R(es) and C(ap) combinations to get the desired frequencies for LED blink speeds.
now; a rather big step up, is to this sine wave generator circuit - and into the audio realm !
haven't fully mastered the various op-amp circuits, but i think i know what is going on the with non-inverting amplifier and the comparator setups.
this sine wave generator is quite complicated because they look like the're looping feedbacks; anyway, for now - i just want to get a sine wave and have it realized audibly.
so; i tried to copy the circuit example below (on the left) except i used a 5V unregulated power supply (i've measured 6V from it before).
the schematic on the right is how i actually rigged it up - please excuse the messy layout - i wanted to ensure it was as close as possible to the actual physical connections so that it might highlight any wrong connections i might have made.
the problem now is - i don't hear anything; not from a speaker (which might be designed to expect more power though) nor some small earphones.
that "Quadrature oscillator" circuit is supposed to give a 1.5 kHz sine wave - so it should be within normal hearing range.
did the change from 9V to 5V change this frequency ? - i'm not sure how to calculate it, but i thought it is dependent on the R and C combinations. (and in this complicated circuit, i'm not sure which to use, although it's obviously 10k Ohm and 10 nF ! [and using f = 1.4/((R1 + 2*R2) * C) would give 4.8 Hz (??)]
would appreciate if anyone could give some pointers what to look for in trouble-shooting why nothing is happening with the circuit i built.
EDIT:
sorry - that ACTUAL SETUP is missing a 10k resistor from "2" to "7" - but it's there on the breadboard though, also as a potentiometer to play with the sine wave.