[sdiy] Last question about LFOs

[Magnus Danielson]

Dave,

David G. Dixon skrev:
> Well, my custom-designed shape-shifting triple LFO works perfectly, and the
> LEDs are happily blinking away.  However, I'm not sure about the capacitor
> values I chose.  I selected 10 uF (non-polar) for the "long" cap and 33 nF
> for the "short" cap.  This way, the long durations range from about 4
> minutes to just less than 1 second, and the short durations range from a few
> seconds to about 2.8 ms (360 Hz).  I wanted a small amount of time overlap
> between the two settings, and I achieved that.  However, there isn't much
> useful "low frequency" range in the "short" setting, as the thing becomes an
> oscillator less than halfway along the rotation of the rate pot.  I'm
> thinking I might want to swap out that 33 nF cap for 100 nF or maybe even
> 330 nF.
> 
> Hence, my question: Is there a "standard" or "accepted" range of frequencies
> for LFOs, and barring that, what is the typical maximum frequency of LFOs?

I think your short setting is running a little high. While it is cool to 
go a bit up in the audio-range, 360 Hz may be a bit high. I'd definitely 
consider dropping it down. Alternatively have three settings.

Try the 100 nF, then maybe 220 nF or 330 nF.

As a side comment, you can make the LEDs blink when only cables is 
connected using a normal diff-opamp setup in which the non-inserted side 
is connected to the - input and the switch input and inserted side goes 
signal and + input. That way, when the connector is unconnected, the - 
input and + input is fed the same signal and essentially cancels in the 
diff-amp setup. When you connect a cable you break the link and the 
cable gets its feeded signal while the cancelation no longer occurs and 
the LED blinks. A transistor pair could play the same trick, but this is 
one way to use a 741 if you have one lying around...

Yeat a simpler method is to feed the signal on the switch side and let 
the inserted end feed the LED. What works best for you depends a bit on 
the connector.

But then, I like it when they blink... and it is so much simpler.

Cheers,
Magnus