Super Simple Oscillator + Behringer Crave. Voltage question

[fredrik]

If you check the oscilloscope output in this post:

Getting the SUPER SIMPLE OSCILLATOR to oscillate

The SUPER SIMPLE OSCILLATOR keeps causing headaches, because while it’s a SUPER SIMPLE CIRCUIT (and SUPER CHEAP; the active component costs you a couple of cents) it’s not necessarily a SUPER SIMPLE BUILD, as can be seen in the recurring “oscillator trouble” threads in this forum. So I thought I’d post some suggestions for how to build the oscillator step by step, in a way that will at least tell you if you’ve managed to get it to oscillate. I’ve tested this with a variety of transistors, and h…

you’ll see that the output signal swings between 7.4 V and 10.7 V for the 2N3904 I used there, so while the swing itself is within bounds, there’s a strong DC component – i.e. the output swings around (7.4 + 10.7)/2 = 9 V, not 0 V. You could add a capacitor in series with the output to filter that out, see e.g.

Trouble with the Super Simple Oscillator

The oscillator will swing between the transistor’s breakdown open and close voltages, which will result in a fairly high DC offset; see the oscilloscope picture here for an example: (that specific build swings between 7.4 and 10.7 volts, which corresponds to a DC offset of almost exactly 9 V) Depends on your mixing desk if that’s a problem. If you have an AC coupled input with ok headroom you can just plug it in as is. To filter, you can try anything from, say, 100 nF upwards. Line inputs ar…

(I’d be a bit surprised if you damaged your Crave by feeding in the signal as is, though, but better be safe than sorry, I guess.)