VCO

[BJ]

Grant Richter wrote:
> The VCO's in the phase locked loop IC's (CD4049, 74ACT4049) work very well

Hmm,,to my mind the 4049 is a hex inverter, but I do belive you ment the
4046.

> as high frequency oscillators. Even if you don't use the phase locked
> portion. A straight CD type with a 10pf cap runs up to ~5Mhz and my
> frequency counter showed the ACT type running up to ~43Mhz. Since these are
> linear VCOs you could use an exponential volt to volts converter (like an
> EML101) to make a 1V/Oct. unit. I don't know if they are linear enough to
> pull this off over an extended range.

Yes, the linearity are no good in the 4046 and to all of you thinking of
implement this kind of design to drive a wave table, should take a close
look at the shematics of an OSCar.And also have a close listen to the
sound when rapidly switching from a low note to a high and vice versa.
You are then discovering one of the drawbacks of this kind of PLL/OSC
implementation.

Any one test'ed the 74HC7046/74HC9046,a new design of the old 4046PLL?

> My current project is to replace the PLL/Counter circuit with a high speed
> DAC run off a sawtooth to generate the address bits. This is bound to be
> imperfect but then again it's music not space shots. This has the advantage
> of allowing different sweep types depending on the input waveform. This
> also makes the wavetable board truely an add-on waveshaper.

This might bee a good idea too.

By the way,Ii think you have a wery nice and competetive thing with the 
Waveform City module.Please continue....

BJ