9v and VA and VB???!!!???

[darko28064212]

hello all,

i have a question concerning my build but can also shed light on other future projects. im bulding the Rothwell Love Squeeze compressor pedal from a popular vero layout found at sabrotone.com. i have all the components to build but am currently at a stand still with the voltages required. obviously 9v, but im also looking at the schematic of the Love Squeeze and there is VA and VB also listed in the circuit. what are they representing and what are the voltages of them? i could be making this harder than it is but its what is holding up my progress at this point.

any input is appreciated!

Cameron

[m-Kresol]

9V is your input. VA is the voltage you have after the polarity protection 1N4001 diode and 22R resistor. VB is the bias voltage, in this case it should a little more than half your VA voltage, so I'd guess around 4.5V. The names and circle symbols are used in eagle cad for naming nets, so you don't have to draw a line all over the schematic. Nets with the same names are tied together automatically.

[darko28064212]

ok so if VB is bias how is the bias obtained how do you have a 9v source and a 4.5v source?>

[davent]

R6 & R7 form a voltage divider, Vb is taken from their connection, c6 filters Vb.
dave

[m-Kresol]

As Dave mentioned, R6 and R7 build a voltage divider. For the sake of simplicity lets assume both are the same resistance value, eg. 10k, and the voltage going into R6 is 9V straight.
R7 is connected to ground, so the complete 9V have to drop over the combined 2 resisitors. Since both resistors are the same 10k resistance, they equally share the voltage drop, so the voltage drops 4.5V over each of the single resistors.

In our specific case, R6 is a little less than R7, so the voltage drop over R6 will be a bit smaller too. But don't forget that you don't deliver 9V straight into the voltage divider (theres the 1N4001 before which will cost you a bit due to its forward voltage), but a bit less, so I just approximated 4.5V.

hope that makes sense. you can read up on wikipedia too: https://en.wikipedia.org/wiki/Voltage_divider