[sdiy] 4006 on evilBay

[Tom Wiltshire]

On 11 Feb 2011, at 22:37, Colin f wrote:

> 
>>> BUT - you won't get the CMOS voltage range with either a 
>>> microcontroller or a CPLD without level translation.
>>> 
>> 
>> So, a microcontroller and an opamp, then?
> 
> Not quite.
> You'll need +5v to run your micro.
> The TR909 uses two 4006 and a 4070 for its noise generator.
> I built a functional equivalent of it noise with a PIC, 7805 and a couple of
> caps, and an NPN + 2 resistors for level shift.
> Around 4ukp in parts IIRC. Could have used a zener regulator to save a few
> pence over the 7805, I suppose.
> 
> Cheers,
> Colin f

Some PICs have an open drain output too, so you can do the level shift without adding the transistor. It can be done for under £2, I'm sure, particularly if you've already got a 5V supply (as you have in many synths).

T.