Why smooth the "Vgg" voltage on MN3207/MN3007 delays?

[DrAlx]

Every schematic I've seen for a MN3207/MN3007 based effect has a smoothing capacitor for the Vgg (=14/15 Vdd) voltage for the BBD.
It's even in the example circuit in the MN3207 data sheet ..
Well I was recently looking at some detailed gut shots of the FoxRox Paradox TZF and worked out that it does not use those capacitors
at all.  Each BBD has a simple voltage divider for Vgg based on a 15k and 150k resistor, and no smoothing cap.
So that gives Vgg = 150/165 Vdd.  It's about 3% error on the required 14/15 ratio.
I figured if a highly-rated stompbox like the Paradox can get away with a 3% error on Vgg and no smoothing, then the cap must be kind of pointless.
As a test, I took the Vgg cap off a BBD in one of my builds, and then touched the leads against the pins on the BBD to see if reconnected it made any difference to the sound or noise. 
I could here no change whatsoever.   I'm now thinking that the Vdd voltage for the BBD usually has a smoothing cap on it anyway, and that further smoothing on Vgg won't do much.  Does anyone have a good explanation for why Vgg smoothing is necessary or a good idea?

[Fender3D]

Vgg is just a reference voltage for mosfets inside BBD...
It'd be a good practice to smooth reference voltages with cap(s).

As a side note:
playing with Vgg you'll notice variations in BBD's output level and bias requirement.

[Mark Hammer]

My guess is that since the Vgg is often adjusted via a trimpot at the factory, maybe the smoothing cap simply expedites the process of setting the bias right.  In other words, maybe the cost of the cap is less than the cost of the labour in the absence of the cap.  And given that Dave Fox doesn't churn out quite as many pedals as Boss or DOD or MXR do, maybe he has the latitude to take that extra time.

But that's just a guess.

[PRR]

The 14/15 ratio is approximate, and perhaps not super critical. There's an internal rail which has to be less than the supply.

This internal rail is part of the audio transfer process. It should probably be super-clean, whereas the power pin probably does not have to be so clean.

If there is any doubt about the cleanliness of the main power, a cap on Vgg is a good way to clean what matters without major cost or effort.

OTOH, sometimes Vdd is "known" to be clean (or not dirty enough that its dirt to the Vgg rail will offend customers) so the cap could be omitted.

Don't overlook the possibility of a simple designer's oversight. There's a lot of parts to keep track of. And if actual-use does not involve dirty power supplies, the oversight may not be noticed.

[Dave W]

heres a design where Vdd=Vgg....
http://www.morleypedals.com/sfbes.pdf

[DrAlx]

heres a design where Vdd=Vgg....
http://www.morleypedals.com/sfbes.pdf

Funny.  I'd seen that schematic before but overlooked that.
I did a bit more experimenting and agree with Fender3D (it's sensible to smooth all voltage references).
I noticed that not only does the Paradox not bother with smoothing Vgg, but it doesn't smooth the BBD bias voltages either !!!
I am guessing that having compander chips in the circuit lets you get away with taking liberties (or making accidental oversights) in other places.

[Lurco]

heres a design where Vdd=Vgg....
http://www.morleypedals.com/sfbes.pdf

The BBD operates from 9V, while Vgg comes from the clock circuit at "A", where the 9V wanders through a resistor first, before becoming a Vdd supply for that subcircuit. So Vgg<Vdd there at the BBD chip.

[puretube]

Why smooth @ 93 % of the P.S., when that is perfectly smoothed  @ 100% ?
...and it is not especially recommended in the Belling datasheet?