Schematic questions

[Jay.lingelbach]

Question on an aion fx schematic about some labels and what they mean.

https://aionfx.com/app/files/docs/radian_documentation.pdf

It's for a rangemaster. VA, -VA and pwr_gnd.

I've googled it and VA came up with "A volt-ampere (VA) is a measurement of power in a direct current (DC) electrical circuit." I'm not sure how to translate that to english or eagle lol.

And power ground doesn't really return anything useful. Maybe ya'll would have some better answers for a newb?

Jay

[mauman]

"VA" is just a designation for V+ or positive voltage, in this case the +9V from your battery or power supply once it's been protected and filtered.

"-VA" is the negative 9V generated by the charge pump IC1, since this is a positive ground circuit (ground is more positive than battery.)

"Power ground"  (three horizontal bars) is the ground for the power circuit.  "GND" (little triangles) is the ground for the audio part of the circuit, which some layouts keep separate from power ground, to minimize noise, until they're connected at a single point somewhere in the circuit.

<edit> There are also other possibilities that are not used on this particular schematic. 

Vreference (VR) or Vbias (VB) are reference or bias voltages (same thing) for transistors or op amps.  They're used in a single supply circuit (positive voltage and ground) and are often half of the supply voltage.  In a +9V circuit, VR or VB will usually be +4.5 volts. 

And in a dual supply circuit, instead of +V and ground, you'll have +V and -V which are often but not always equal, like +9V and -9V, or +15V and -15V.  Bonus fact: in a dual supply circuit, the halfway reference voltage VB or VR can be ground, since zero is halfway between +9V and -9V. 

[Jay.lingelbach]

Thank you so much!

[mjg]

Another way to look at is that you just need to join up all the things with the same label.  It could be called "banana" instead of "VA" and it would do the same thing electrically.      

As Mauman explained, there are all sorts of conventions for what these things mean usually...but when it comes down to it, they're labels. 

[Aentons]

Another way to look at is that you just need to join up all the things with the same label.  It could be called "banana" instead of "VA" and it would do the same thing electrically.      

As Mauman explained, there are all sorts of conventions for what these things mean usually...but when it comes down to it, they're labels.

If you hook it up to a banana, it won't turn on.

I get your intent but I would disagree and think It's better to know what things mean.

[jimilee]

Another way to look at is that you just need to join up all the things with the same label.  It could be called "banana" instead of "VA" and it would do the same thing electrically.      

As Mauman explained, there are all sorts of conventions for what these things mean usually...but when it comes down to it, they're labels.

If you hook it up to a banana, it won't turn on.

I get your intent but I would disagree and think It's better to know what things mean.

But what about a potato?

[mjg]

Lol, yeah, don't use a potato, we saw how that turned out in Portal. 

Sure, I totally agree, it's good to know what these things signify.  Just offering an alternative 'quick start' if you want to just follow the schematic by numbers.