ADD: Tremolo

[tomg]

On 30-Oct-98, Mark Grocholski wrote:
>tomg wrote:
>> 
>> Made a few changes after talking with Art. If you
>> are planning to build one of the trems take
>> another look first.
>> 
>> http://www.mindspring.com/~vco/effects/page_001.html
>> 
>> -tg

>on these schematics is "RANGE" like Depth or Intensity on other
>tremolos? On the second one, what does "BIAS" do?

Yes. You can call it depth if you like. The BIAS trimmer is a
variable voltage divider. It allows you to bias the op-amp
oscillator for proper 9V operation. 

bias - a fixed voltage applied to whatever..(in the old days
electrode) causing a tendency to do whatever.

Most op-amps are designed for split supplies (+- voltage)
if you want to run them from a single supply (like +9v) it 
must be fooled by using a bias voltage source. A voltage 
divider is easy to come by just split the supply with a 
pair of resistors or use regulators, zener-ref... whatever.
 
There are several scattered liberaly about this circuit.
the 100K/100K divider is for amplifier bias suppling 1/2
the +V and the 100K/470K for fet bias. You can look at 
these bias points as fake grounds effectivly turning
real groung into a fake -V. 

For example if the circuit were connected to +-V anything
connected to a bias divider could be connected to gnd
and the divider resistors/trimmer removed.

-tg