Resistor values

[GibsonGM]

MY farmer's "analysis" is that 27R/220u LPF gives a cutoff of ~27Hz.  This is well below normal ripple voltage for a common pedal power supply.

The divider is 20k total; so you have 4.5mA going thru it.  The 27R allows ~300mA "on tap", so that is more than fine (greater than 10x), and the opamp certainly can't be within that range of current requirement!

If you changed 27R to 47R, your cutoff would be ~15Hz, with almost 200mA available...better filtering still, tho less mA for the opamp (did not check how many mA the opamp needs).  A lesser value R would raise the cutoff frequency and also have to dissipate more power.

[MikeA]

Doesn't the in-line Schottky D1 also contribute significantly to the LPF with C11?

[GibsonGM]

Based on the data sheet, D1's capacitance is only 110 pF....only a concern at RF...

[MikeA]

I probably don't know what I'm doing, but when I simulate an RC LPF in LTSpice, like a 27R in series and 220uF to ground, I get your corner frequency figure of ~ 27 Hz.  If I then replace the 27R with a 1N5817 in the forward direction, I get a lower corner frequency and a faster roll-off.  Can't say I understand the mechanism, though...

[antonis]

@Sir Mike: I think that 4.5mA isn't the sole current consumption..

@MikeA (w/o address): In case you implement an AC signal in LTspice, 1N5817 acts as half-way rectifier..

[GibsonGM]

Of course not...I can only 'estimate' what the opamp will consume at this time, however.     I'm a potato farmer / house painter.

Do tell, Antonis! 

[MikeA]

Mike & antonis, I breadboarded it this morning to ensure LTSpice wasn't lying to me.  The diode + cap do rectify AC and establish a small DC offset.  If we're wanting to filter AC noise on a DC bus, diode + cap work pretty well.   With a diode present, adding a resistor in series (as in the OP's circuit) would do more to reduce the supply voltage than to reduce any AC signals. 

[antonis]

The diode + cap do rectify AC and establish a small DC offset.  If we're wanting to filter AC noise on a DC bus, diode + cap work pretty well.   With a diode present, adding a resistor in series (as in the OP's circuit) would do more to reduce the supply voltage than to reduce any AC signals.

I'm not sure if I follow you right, Mike..

It should more enlightening to make a discrimination between AC waveform (+/- fluctuation around  x-axis "zero" ordinate) and DC ripple (only + fluctuation much higher than X-axis)..
The former is semi-rectified by series diode (with a diode forward voltage drop "gap") where the later simply maintains the ripple unaffected..
(it just lowers the ripple waveform by a forward voltage drop..)

[stallik]

Wow! Such enthusiasm.

Yup. Thats the norm around here. Ask a question, get accurate answers then stand back as the discussion deepens and wonderful snippets of information emerge for the willing to pick up. On subjects only vaguely associated with pedals sometimes. Rare precious and beautiful this place.

Glad you got it working