Mini Moog A440 ref circuit

[rarecomponent]

I made this circuit up as a stand alone reference unit for my modular but I never got it working_ I didnt pursue the problem however but as there are very few A440 reference circuits out there
I thought I would have another go
Has anyone made this unit as a stand alone ? ,(and got it working )?

[thealien666]

I use my iPad (iPhone) for that. Much more reliable. The Minimoog reference was a great idea and was more practical then using a pitch fork, back in the seventies. But today's technology offers an even more precise reference readily available, on guitar tuners, smart phones, even another digital keyboard. Moreover, the Wien Bridge oscillator circuit design of the A440 reference on the Mini can become unreliable after a while, and need to be recalibrated due to many factors (components aging, trimpot imprecision, etc).

But if a stand alone A440 reference circuit is what you still aim for, there are better (and more stable) solutions out there.
Such as this one, crystal driven.
http://www.theremin.us/Circuit_Library/ ... andard.htm

[rarecomponent]

Thanks ...I would like to stick to Moog but yes a crystal based unit is going to be more stable ..I have one in mind which runs on +5 supply
And it all depends if I get the mini Moog a440 working ...

[thealien666]

I went back and had another look at that Minimoog 440 reference oscillator circuit, and it's quite a simple circuit really. A single +10V sent to the circuit (on one side of resistances R1, R15, R25, R27 and R50), and the output at the negative side of C8.
R27 sets the maximum amplitude of the sine wave, and C17 and C25 are selected for amplitude and frequency trim (between 600 and 1200 pF according to schematics). This is a "feedback" oscillator circuit, so the condition for it to start "feedbacking" depend on certain things. That's why certain parts are "selected", and some resistances are 1% tolerance only.

If all the conditions are right, there's no reason for the circuit not to oscillate.

[analogmonster]

I don't rely on analog circuitry in this case. I built a crystal based circuit with divider chain for my Formant modular, see http://www.analog-monster.de/440hz_en.html