[sdiy] Voltage Divider for 0-30v PSU (+/-15v output)

[ASSI]

On Samstag 01 März 2008, Anthony Bisset wrote:
> The meter shows +/-15v outputs referenced against the common ground
> and all looks well but upon loading the circuit the voltage drops to
> +8v and approx -0.5v...  Obviously we're missing something.

This "split" supply just provides a 0V reference voltage, which actually 
is good enough for a few circuits.  But you can never return current 
to "common ground" because there isn't any.  You'd need to provide a 
virtual ground via a servo power opamp (0V reference at In+, virtual 
ground at In- and Out) or something similar if you need it as a return 
path.  Stability, noise and frequency dependent impedance of this 
virtual ground need to be considered carefully.

> Note the design is taken from the tonal tilt dual 9v battery
> to +/-9v power design on headwize.com

Yes, but they just needed a midpoint reference - not a return path.  A 
discussion of what to do when this is insufficient is at the bottom of 
another page on the same site:

http://headwize.com/projects/opamp_prj.htm


Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk]>+

Factory and User Sound Singles for Waldorf Q+, Q and microQ:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds