Ok, i have a good pure sawtooth at the output of CA3140 but after it
goes though the next TL072 the sound gets mangled and acts like a
lowpass filter. I changed the 68pF cap to 18p and i get a better range
over the octaves, but i have opted just to remove it. I also had to
lower the value of the 330k Resistor because the gain was too high.
Thanks for all your help. It seems to be working fine now.
goes though the next TL072 the sound gets mangled and acts like a
lowpass filter. I changed the 68pF cap to 18p and i get a better range
over the octaves, but i have opted just to remove it. I also had to
lower the value of the 330k Resistor because the gain was too high.
Thanks for all your help. It seems to be working fine now.
--- In cgs_synth@yahoogroups.com, Richard Brewster <pugix@e...> wrote:
>
> Double check all the capacitor values again. A 68pf cap is in the
> feedback loop of the sawtooth buffer op amp. If this is a large value
> by mistake it would act as a low pass filter, cutting off higher
> frequencies. I used 18pf there. It is only to prevent parasitic
> oscillations.
>
> Richard Brewster
>
> josh wrote:
>
> >Thanks for the reply,
> >I'm double checking everything but nothing seems abnormal. When i
> >apply CV it changes octave correctly and can be tuned but the lower
> >notes have so much gain that the upper haves of the signal are clipped
> >and the output is about 6V pk-pk. when i play the higher notes the
> >gain starts to decrease. two or three octaves up the amplitude is less
> >than 1V pk-pk. Should i get a clean saw with this? Is decreasing gain
> >normal for the higher octaves? I'm going to go on the assumption that
> >i have an improperly placed resistor. Does amyone have any suggestions
> >or things to check to narrow down the fault?
> >
> >--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> >
> >
> >>I suggest you look elsewhere for the fault - more likely a wrongly
> >>
> >>
> >placed
> >
> >
> >>component. Using 2% resistors will at most cause a slight
difference in
> >>stability. It certainly won't be the difference between it working
> >>
> >>
> >or not.
> >
> >
> >>Ken
> >>
> >>
> >>
> >>>Hey. I just built the ken stone vco and i am trying to test it. I
seem
> >>>to be having a problem. The oscillator with no CV applied looks
> >>>clipped. When i add higher CV voltages the amplitude decreases and it
> >>>is no longer clipped. It also does not give a clean saw output. It
> >>>looks more like a half rectified sinewave. I believe my problem might
> >>>lie in that i used alot of 2% metal film resistors since i had
alot of
> >>>them already. Does anyone have any sugestions.
> >>>Thanks
> >>>Josh
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>The CGS Modular Synth home page: http://www.cgs.synth.net/
> >>>
> >>>Yahoo! Groups Links
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
>
>>_______________________________________________________________________
> >>Ken Stone sasami@h... or sasami@c...
> >>Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
> >>Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>
> >>
> >>
> >>
> >
> >
> >
> >
> >
> >
> >
>