Hmm, I read on your site that you wanted to clock the 4024 at 5hz or
less. I guess this would do nothing for the filter and you wanted to
use the suboctave outputs as logic, right?
I don't have a scope, so I can't measure the amplitude of the 3140
output, but it seems to be almost as loud as a 5Vpp osc, just a little
less. When I measure it with my DVM it reads a steady 2.18. I guess if
the osc frequency is too high and the amplitude is low then it means
that the FET or the 311 is switching prematurely, before the cap is
fully charged? I'll try a different 4391. The only other fet I have is
MPF-102 and everyone seems to have problems with those.
less. I guess this would do nothing for the filter and you wanted to
use the suboctave outputs as logic, right?
I don't have a scope, so I can't measure the amplitude of the 3140
output, but it seems to be almost as loud as a 5Vpp osc, just a little
less. When I measure it with my DVM it reads a steady 2.18. I guess if
the osc frequency is too high and the amplitude is low then it means
that the FET or the 311 is switching prematurely, before the cap is
fully charged? I'll try a different 4391. The only other fet I have is
MPF-102 and everyone seems to have problems with those.
--- In cgs_synth@yahoogroups.com, "djbrow54" <davebr@...> wrote:
>
> My VCO didn't run correctly the first time either. With a scope I
> could see that the ramp output of the VCO (pin 6 of the CA3140) was
> very low amplitude. I replaced the MPF102 with a different FET and
> it worked fine. I have no idea why the original FET didn't work.
>
> The clock mod is for very low frequency response. The clock is
> capacitive coupled and there just isn't enough voltage swing to
> trigger the clock input of the 4024 at VERY low frequencies. I DC
> coupled mine so it wouldn't be an issue.
>
> Richard Brewster later posted something with the PCB trace not
> matching the schematic in this area. I don't know if he had an early
> PCB or what the issue was. Search for message 2164. This only
> affects the output of the 4024, not the VCO output.
>
> Check the VCO output on pin 6 of the CA3140. You can just connect
> this to an amplifier through a suitable capacitor to remove the DC
> bias. This needs to be working correctly before verifying the 4024.
> If it was like mine and only had 1V pk-pk - then the low frequency
> range is quite limited. It also could be an issue with the LM311
> voltage comparator.
>
> Dave
>
> --- In cgs_synth@yahoogroups.com, Tom Adam <tom.adam@> wrote:
> >
> > I'm about to build my bi-n-tic and I came across this link.
> > Check the clock driver mod. Is this what you're seeing?
> >
> > http://modularsynthesis.com/cgs/bi-n-tic/bi-n-tic.htm
> >
> > Cheers,
> > ToAd
> >
>