Shaka Express Questions - Geofex PCB layout

[statorvane]

Hello,

First post here. Found this place from the AX84 website. My son and I were listening to various Shaka sound clips and, while they all sound pretty good, we are awestruck with the Express clips. I found the schematic for it, and a PCB layout at Geofex. I also found a perfboard layout, but the component values and content do not match the Express schematic. That is, the PCB appears very close to the schematic. I have several questions about the PCB layout.

When I compare the PCB and schematic,  I do not see the +18 V supply to the PCB; there is only provision for a "+9 volt Batt" input. I assume there is a voltage doubler circuit on the PCB version.  Is this correct?

The PCB layout includes a capacitor labeled C14 - is that the 47 uF electrolytic cap from a voltage doubler (second page of the Shaka Express Schematic)? There is no reference to a "C14" on the schematic.

One more. The C6 capacitor (22 uF) on the PCB layout, I assume this an electrolytic capacitor. It appears to be a bypass cap for R6 (schematic), but  I do not see where the cap is grounded (PCB). I assume there must be a jumper attached to ground?

Thank you.

[aron]

I don't think there is a voltage doubler on the PCB, you can use 2 batteries instead - wired in series. Yes, C6 looks ungrounded -  it looks like it's for R7.

[statorvane]

Thank you kindly sir. As I am finding my way around here, I found some information grepping through the older posts...

The middle capacitor labeled C14 is the 47 uF electrolytic used in the power supply voltage divider.

The "+9volt Batt" annotation on the PCB is probably the "V+" input (18 volts) on the schematic - there is a voltage divider on the board to produce 9 volts from the 18 volts as a reference voltage. It appears several folks have run this at 12 volts and reported good results.

The cap labeled C13 on the PCB is not the same as the C13 between the Tone and Vol pots. It appears to be the "power supply filter cap to lower the supply impedance" mentioned in the PCB notes; e.g. 47 uF or more.

One post mentioned several jumpers missing. I found one (C6 to ground), but haven't found others yet.

The voltage divider before T3 (Ed Rembold mod) is missing a second resistor (R22). The schematic indicates these should both be 470Kohm, so it appears the voltage is dropped 50% to the last Op Amp. Similar to R8/R9 before the 2nd FET.

Hope this helps others that may have the same questions.