Snow White Autowah Build - possible error in vero layout?

[ItsGiusto]

I'm going to shortly start a build of a mad professor snow white autowah, using this layout:
http://tagboardeffects.blogspot.com/2013/04/mad-professor-snow-white-autowah.html

I think I found a mistake, though, in the layout. I commented on the original post at tagboardeffects, but there have been no replies - I think that thread's been dead for a bit. So I thought I'd run my find by y'all as a sanity check to see if I'm correct.

There seem to be two capacitors coming directly off of ground, run in parallel to the input of the one of the opamps in the lm324. This is strange, because a 47u capacitor run in parallel with a 100n capacitor is just the same as a 47.1u capacitor.

See this image with the two caps circled:



I think maybe the 47u cap is supposed to connect to the other end of the 47k resistor, so it's on the same band as the "I" input of the voltage regulator. That it's supposed to be C7 here:
https://elektrotanya.com/PREVIEWS/63463243/23432455/egyeb/mad_professor_snowwhite_autowah_guitar_effects_schematic.pdf_1.png
The only problem is, it's not the right value to be C7 (47u vs 100u)

Please let me know if you this is actually a mistake or not, and what the layout might be: I'd like to know before I start building this!

[duck_arse]

that opamp section is being used as the Vref/Vbias buffer. the 47uF will provide the bulk of the ref smoothing (boom boom), with the 100nF (should be ceramic or similar) providing the higher freq smoothing/bypassing (tweety tweet). the 100nF is not necessary, but good practise. the value of the 47uF is not critical, can be anything from 10uF ~ 100uF, will work fine (maybe 100uF a bit slow).

[ItsGiusto]

Are you saying that it's actually correct on the original diagram?

[duck_arse]

I will say it is correct on the diagram in your first post this thread. I will also say it doesn't really matter - the whole circuit operation does not hinge on the value of those two caps, or if they are both fitted. as long as you have at least some capacitance there, it will do the job. (I don't see the 100nF cap on the circuit diagram we looked at in that other thread).

[ItsGiusto]

Cool, thanks for all the help!

[slacker]

That it's supposed to be C7 here:
https://elektrotanya.com/PREVIEWS/63463243/23432455/egyeb/mad_professor_snowwhite_autowah_guitar_effects_schematic.pdf_1.png

C7 on the schematic is the 100uF cap bottom right on the vero layout, if you trace the big jumper up the middle of the board you'll see it connects the cap to the row with the input of the 7805 regulator on it. Maybe the 47uF cap is a mod or the layout could be based on a different schematic, like Duck said it will work fine with or without it.