Very early NS-2 Schematic, need advice.

[william]

I've been working on the NS-2 schematic I've been making a huff about recently.  I've come to a few issues and would enjoy some advice.  I initially thought there was a +1/2V supply in the schematic but now believe it carry's the audio signal.  The main audio signal also seems to only go to the envelope follower.  I have provided a link to what I have accomplished thus far.  The only parts missing are the Mute/Gate switch and the switching arrangement.  Also, the area around the send jack could be refined to be clearer.  I'm also unsure if I have all the transistors orentated correctly.  The upward pointed arrow with no label is what I believed was +1/2V but now believe to be audio.  Thanks for taking a look.

The schematic.
http://209.240.71.22/web/NS-2_Prelimenary.gif

The PCB with Notes.
http://209.240.71.22/web/ns-2tracks.gif

[yano]

I don't really see how that arrow could be audio. Is there supposed to be signal coming from a source other than the input and return jack?

I'd imagine that the arrow is indeed +1/2 the voltage.

Notice, on U1 (the U1 near the return jack) and U2, pin 5, the + input, is connected to this triangle. On the U1 next to the send jack, there is also +1/2 going through the 42k resistor. This is to bias the signal, so it has a +4.5Vdc (in this case) offset.

The reason for this is if the signal is not biased, then it will be clipped. That is, if the signal is left at a 0V offset. Check out these diagrams: It shows the basic opamp setup, and then has a graph of the two inputs and the resuting output.









Notice that on this one, the output is 180 degrees out of phase with the orignal signal input. That's because the signal went through the inverting output. Reversing the connections doesn't change the phase, you just get out 0Vac and 0Vdc.


Another way to deal with this is to use a bipolar power supply and connect -9V to the V- and +9V to the V+. Then you don't have to bias your signal.

The signal's offset basically just has to be between the low power input and the high power input on your opamp.  Otherwise it will be clipped, so if you have a signal that has a greater amplitude than say 9V peak to peak, then you'll get clipping no matter what when you're using 0-9V supply with a 4.5V offset