Thanks :)
Yes, I will fit a 1590B. 21 colums wide is the maximum width for that.
I made this picture that shows the flow of 9 volts (pink), GND (gray) and Vref (green)
As you can see, R2 connects to ground through the link under the IC
(it's a double link at IC pin 4, I should probably make a note of that on the layout since it's easy to miss).
9 Volts + goes through D3 (for polarity protection, I decided to add it in series insted of between +9v/gnd so it's a bit different from the schematic)
then it goes through R23 which is a 100R resistor (that's another modification by me, R23 in the schematic was the LED resistor or something).
R23 and C15 forms a lowpass-filter on the DC-network which removes and AC ripple coming through from the powersupply that can cause a high pitched squeel.
So anything connected to 9v after the 100R resistor can be considered a direct connection to 9v (only filtered).
The green area is Vref, made up of the resistors R22 (goes to 9v) and R21 (goes to ground) that forms a voltage divider and gived you around 4,5v.
I hope that helps you. Please just ask if you have any more questions
cheers
/ Fredrik
check out my building blog at www.parasitstudio.se