It seems like I am the only ******* left alive on Planet Earth.
Has everyone died?
I have NOT.
Anyway, I have revised my page about the Wien Bridge oscillator with re-done schematics including many new details.
See
http://www.turneraudio.com.au/Wien-b...scillator.html
I will estimate its The Most Boring website page ever devised, unless you'd like to make a half decent signal gene.
Of course, I have used a rotary two wafer make-before-break switch that gives 12 F per decade evenly spaced around a dial at enough convenient F to allow plotting most F reponses of any audio gear tested, unless a high Q resonant filter is used, because the adjustablity of a pot of variable C is not present.
For audio amp checking the unit is quite sufficient. Those wanting infinitely varaible F should consider buying a dual gang reverse direction log pot with value 15k. Lord Noze where you'd obtain one, and one that gave you nicely spread out F around 315 degrees of rotation with 1Hz at the max anti clockwise and 10Hz at max clockwise and 3.2Hz at 1/2 rotation.
With a bigger box and slightly more range switch complexity you might incorporate TWO 3 gang AM radio tuning caps with each gang 40 to 440pF thus giving 132pF to 1,320pF which is fine for 100Hz to 1MHz, with fixed R values. The two ranges 1Hz - 10Hz, 10Hz - 100Hz could use a pot with fixed C and values are not difficult to implement. The variable tuning gang as was made in 1950s is hard to beat for a WB oscillator but to get down to 1Hz with max C = 1.320pF the R needs to be 120Meg ohms, an impractical R value. But where you had 6 x 3gang C then C max = 3960pF, and if your lowest range was 2Hz to 20Hz, then R need only be 20Megohms.
The minimum C = 396pF, and R need only be 200r for 2MHz. For stable operation at such a high F you need low value R and C high enough so stray C in devices does not make F adjustment too critical. The j-fet in NFB network for Vo control should work up to 2MHz.
HeeLLLLOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO? anyone there? Ah, they all musta died.
Think I'll go ride a bike, and even being attacked by magpies is just fine.
Patrick Turner.