[sdiy] Hewlett oscillator

[Laurie Biddulph]

The 8038 actually has a 1% sine wave output after adjustment and can be 
taken to 0.8% with the right chip variant. Triangle is less than 0.1%

Best Regards

(Mr) Laurie Biddulph
Phone: +61 (0)2 4340 0938
Mobile: 0400 257 645

Elby Designs
ABN: 70 022 727 605
http://www.elby-designs.com

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----- Original Message ----- 
From: "Dave Leith" <dave.leith at gmail.com>
To: "Aaron Lanterman" <lanterma at ece.gatech.edu>
Cc: "sdiy DIY" <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, November 29, 2008 7:29 AM
Subject: Re: [sdiy] Hewlett oscillator


> Re: Wien bribge
>
> I believe that circuit looks like the oscillator that's used in the
> Maestro Ring modular. I replaced the 2 R's with a dual vactrol to get
> a basic voltage control (almost linear :-) of the circuit - it's kinda
> nice.
>
> On Fri, Nov 28, 2008 at 11:46 AM, Aaron Lanterman
> <lanterma at ece.gatech.edu> wrote:
>>
>> 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
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