Cherry Audio Forums

Hi,

Maybe I'm missing something here, but it seems the whole point of the Beat function of the oscillators has been missed.

The way it is supposed to function is that whatever frequency the Beat between the oscillators is set to stays the same over the range of the pedal board, yet it seems to behave like regular analogue synths that increase frequency beating the higher up the keyboard you go.

Any chance of a fix?

Slightly tangential, and apologies in advance for the blatant advertising and self-promotion.

I made sure that the two oscillators of Bully Beef had a constant frequency difference regardless of pitch. YouTube Demo.

There is a detailed explanation in the Bully Beef User Guide.

All the Bully Beef Presets can be played on Voltage Modular Nucleus Edition and other free-of-charge modules. So you can get a pretty good approximation of that classic T**rus sound for only $2.

I don't know where this myth started, but the constant beat rate with frequency thing is just that. The Taurus I had that was used for cloning reference did not exhibit that behavior. The beat increases with note value. A careful look at the schematic clearly reveals the cause. The BEAT knob detunes the second VCO.

==The technical details==
The Taurus uses a linear VCO. The exponential behavior comes from a specialized resistor ladder on the pedalboard. Therefore, the linear VCO responds to an exponential voltage / note. The VCOs are actually ICOs (current controlled oscillators) and require a control current rather than a voltage. This means that the tuning controls must be wired as variable series resistors which convert the control voltage into a current. This is completely different from the grounded 3-terminal potentiometer arrangement to vary a control voltage. The BEAT knob is just a small value pot connected in series with the larger value tuning pot (they simply add their values) which is connected to the control current input of VCO2. All proportionality remains the same. Every octave always goes twice as fast because the control current always doubles with every octave. Therefore, the beats will double in rate as well. There is no mechanism to keep the beat frequency constant.

Clear as mud -- I know.

--mb