finished cgs vco

arnoid · Joined: Aug 23, 2009 Posts: 57 Location: Belgium

Hi i'm new on this forum and also a beginning diy'er Smile

I'm busy building a cgs vco with al the options (suboscillator, waveshaper,...).
I finished it and everything seems to work exept the pulse output of the suboscillator I get no output , If I look with my scope and turn the S TRIM fully CW I see the beginning of a pulse waveform.
It's like the trimmer's range is not big enough, I'm using a 22K trimpot.
Somebody knows what the problem could be ?

I also noticed that the outputs of the waveshapers saw to sine AC & DC are less louder then the outputs of the waveforms of the oscillator.
Is this normal ? the diffirence in volume is quiet big...

andrewF · Posted: Thu Oct 29, 2009 9:02 am Post subject:

Hi
do you have the SQ output connected to the STI input?
if you are using jacks you can wire the switches of the jacks together or just patchcord, if banana sockets use a patchcord.
Also at some pot settings the sub-osc has no output.

re: sine outputs, does adjusting WS trim help at all?

and seeing all these problems involve the LM3900, have a good check it is getting proper voltages, grounded, etc.
Usually best to suspect the chip after exhausting other possibilties.

have fun Very Happy

arnoid · Joined: Aug 23, 2009 Posts: 57 Location: Belgium

thx for you fast answer Smile

No I didn't wire the SQ output to the STI in (is this nesseccary to have a pulse output at the suboscillator ? ) I'm working with banana's so a patchcord is fine then...

I also mailed ken stone about the waveshape outputs he says it's normal that they are less louder then the waveform outputs of the oscillator..

andrewF · Posted: Fri Oct 30, 2009 5:01 pm Post subject:

zthee · Joined: Feb 20, 2008 Posts: 414 Location: Stockholm

I find the output of the sub oscillator to be very narrow - anyone else experiencing this?

arnoid · Joined: Aug 23, 2009 Posts: 57 Location: Belgium