[sdiy] Sound Lab Mini Questions

[Rude 66]

hi ray,

thanks for the tips. unfortunately, i don't have a scope here, just a
multimeter..;-) i can have access to one some time this week.

in the mean time, i do have a computer. is there any software (free, trial,
demo, etc) that could help here?

thanks!


ruud


----- Original Message -----
From: "Ray Wilson" <raywilson at comcast.net>
To: "Rude 66" <r.lekx at chello.nl>; "john mahoney" <jmahoney at gate.net>;
"Synth-Diy" <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, June 20, 2004 5:38 PM
Subject: Re: [sdiy] Sound Lab Mini Questions


> Hi Rude
>
> > osc 2 is still problematic. by itself, it isn't there. i've patched mine
> > out, and if i give it a cv from osc 1, it sounds but very weakly. it
> sounds
> > like a weak copy of osc 1, but by also giving it an lfo in (long live
> banana
> > plugs)  i could determine that the sound was indeed osc 2 as osc1 was
not
> > affected by the lfo.
>
> If you look at the output of IC6-D (pin 14 of IC6) you should see the raw
> sawtooth wave
> output of Oscillator 2. You should see a very narrow positive going pulse
> wave (a few uSecs) at the same
> frequency at pin 8 of IC6-C. If the sawtooth is there the pulse is
> definitely there. If neither of them are
> there then check all the components associated with Osc 2 for correct
values
> and good soldering. If you used
> a sub for the MPF102 make sure the leads are oriented correctly.
>
> Next look at the output of IC2-A pin 1. You should see a rectangle wave
> whose width will depend on the setting
> of of R85. The width should vary quite a bit as you adjust R85 and in
> conjunction with the LFO switch turned on
> may fade in and out as the bias at pin 2 of IC2-A becomes higher (or
lower)
> than the amplitude of the signal at ZZ.
> By adjusting the level of the LFO and the setting of R85 you should be
able
> to get good PWM without the pulse
> wave going away. With S15 off you should be able to get from 10% to 90%
> pulse width variation using R85.
> If this is not what you are seeing then look over the panel wiring to make
> sure that R85 is connected on both sides to
> +9V and GND through the correct value resistors.
>
> Look at the bottom of the Sound Lab page for more trouble shooting info on
> the PWM and noise circuits.
>
> >
> > it's only giving sound though when the frequency knob is sort of in the
> > middle. when turned either way, it fades out almost like the pulse width
> has
> > gone too far. i can't get pwm to work either, but that's a later
> worry..;-)
>
> The pulse width should not vary so much as you adjust the frequency that
it
> disappears unless it is
> adjusted to a very narrow pulse.
>
> >
> > i'm missing noise (also not a main concern) and the trigger knob doesn't
> > work. vc in works, the gate input works, but i can only hear it when the
> > vca's initial gain is open pretty far. it's there, but it seems to weak.
>
> See the bottom of the Sound Lab page.
>
> >
> > any ideas on this before i start diving into the rat's nest? ;-)
> >
> > but even with one vco, filter, lfo and eg it's already one hell of a fun
> > box!
> >
> > r./
> >
>
> I hope this helps
>
> Ray
>
>