[sdiy] Hewlett oscillator

[Aaron Lanterman]

On Nov 27, 2008, at 4:42 PM, Grant Richter wrote:

> For an onboard sine source, your best bet would be a single op-amp  
> Hewlett design with an incandescent lamp for soft limiting.
> Both the ICL8038 and XR2206 have sine waves with a THDs of 5%, this  
> is not good.
> The Hewlett design should have a THD of less than 1%, much better.
> This sine wave can be normalized to the SIGIN jack, then if you need  
> voltage control of the carrier frequency, you can patch it externally.
>
> The on-board sine source can then be a simple potentiometer control.  
> A suggested range is 10 Hz to 1kHz.
> Adding a wider range is not musically useful, at a 1kHz carrier  
> frequency everything is shifted so high it's almost inaudible.
> Th simple sine source should have a panel output also with a 1K  
> resistor in series.

Some Wiki foo brings me this: http://en.wikipedia.org/wiki/Wien_bridge_oscillator

The design I see there has two Rs, so I guess I'd need a ganged pot?  
Or is there a way to work around it to use only a single pot?

- Aaron