Wait a minute. The PWM input does not need to be connected up. The
100K resistor to ground from the - input of the comparator sets the
detection point to zero. And the AC-coupled sawtooth wave going to the
+ input of the comparator centers the waveform around ground. So
without anything else connected you should get a nice square wave from
the SQ output.
-Richard Brewster
http://www.pugix.com
sasami@... wrote:
100K resistor to ground from the - input of the comparator sets the
detection point to zero. And the AC-coupled sawtooth wave going to the
+ input of the comparator centers the waveform around ground. So
without anything else connected you should get a nice square wave from
the SQ output.
-Richard Brewster
http://www.pugix.com
sasami@... wrote:
>> I connected the PWM to a front panel jack. Did you mean the SQ wave
>> doesn't work when there's nothing modulating the PWM input? Or that
>> it has to be connected to the front panel?
>>
>
> It needs an input, usually from a pot, to work. If it doesn't have one, the
> detection voltage the op-amp is seeing is outside the range of the signal.
>
> Ken
>
>
>> Cole
>>
>> --- In cgs_synth@yahoogroups.com, sasami@... wrote:
>>
>>> 1) Use a different VCO output. The square wave likes the PWM input to be
>>> connected.
>>>
>>> 2) Sweep the tune knob, and if you still don't hear anything , try
>>>
>> adjusting
>>
>>> the SPAN and ZERO trimmers. This VCO can quite happily work well
>>>
>> above the
>>
>>> hearing range if these are wrong.
>>>
>>> Ken
>>>
>>>
>