Can anyone suggest an LFO...?

Ojd · Joined: Feb 22, 2008 Posts: 65 Location: Ua Audio files: 1

Wrong diode polarity? Didn't cut traces on stripboard? Contact between tracks (frequent problem of mine)?

nicolas3141 · Posted: Tue Feb 08, 2011 3:42 am Post subject:

If both LEDs are lit then either the LEDs are not opposed as they should be, or the circuit is oscillating at a high frequency (instead of a low one).

So first check the LEDs - are you sure one is facing this way and one that way?

Second, look at the op-amp with the 1uF cap in its feedback loop. It is the integrator. Find the - input of that op-amp. It should be getting fed via a network of resistors/diodes/pots from the output of another opamp. Measure the resistance of that network from the output of one op-amp to the - input of the integrator. Resistance should be approx 100K.

Third, check that all the pins that should be at 0V are actually at 0V. The + input of the integrator especially. And the pots that should have one side at 0V. Check all those points with the circuit running to make sure they are all really at 0V exactly.

Hope this helps.

Cheers,
Nicolas

oozitron · Joined: Apr 02, 2007 Posts: 33 Location: USA

Thanks for the replies & ideas... I think the problem was that I had it on the same board as my ADSR (which isn't working either; see that thread!) and that has electro caps on the +/- power. I built the LFO all by itself and it works perfectly Smile

I'm working on a "rack monosynth" and am now going to build three of these LFOs and have them normalled to the FM and PWM of my JH Living VCOs. Massive...

thanks Nicholas!

synthesist · Posted: Mon Sep 05, 2011 12:46 pm Post subject:

he!
I build the VCLFO and the LFO from nicolas on one board. This circuit rules!!! Cool

It's a nice patch if you plug the saw out of the "normal LFO" at a very slow rate to the CV input of the VCLFO. So the VCLFO output is getting faster and faster then slower and slower and faster adn fsater nda slower adn sowler...
that's exactly what I needed and it works!

The next module will be the ADSR Generator.
Biggest thanks for this one nicolas3141

der Warst · Joined: Apr 09, 2010 Posts: 6 Location: London

Hey,

I hope it's alright that I'm reviving this thread. Those LFO's just look very useful for what I'm planning to do. Especially since I have quite a few LM324's kicking around.
I just wanted to know if the first one can be adapted to a single 5V supply as easily as to 9V.
Also, for using it to control resistance, would you rather suggest to run its output into a Vactrol or a Transistor?

cheers,
Simon

acidblue · Joined: Jun 26, 2009 Posts: 154 Location: The Darkside

Sorry if this is a obvious question but where would one put a rate indicator led
on the LFO and the VCLFO??
Or are the blue leds used for this?

bubzy · Posted: Tue Feb 12, 2013 4:20 am Post subject:

acidblue · Joined: Jun 26, 2009 Posts: 154 Location: The Darkside

something like this maybe?
http://www.pcbheaven.com/userpages/LED_driving_and_controlling_methods/?topic=worklog&p=1

bubzy · Posted: Fri Feb 15, 2013 12:50 am Post subject:

well, check this link out, this is from tim servo, after ANOTHER LFO discussion Smile

http://www.electro-music.com/forum/topic-49449.html

acidblue · Joined: Jun 26, 2009 Posts: 154 Location: The Darkside

Thanks..
You are awesome sir.