WTF does this do???

[AllyP]

I plan to build a Shin_EI octave box but i really fail to see the point in using 2 DPDTs just to switch the octave on/off and the clean on/off!!

I figured I would use one DPDT to bypass and add a clean volume knob. The controls would then be:

Sensitivity, Octave volume and Clean Volume.  With the clean volume all the way down I could have just the octave sound.  I realise this loses some flexability(I cant remove the clean signal during a live set unless it is dialled in to do that) but i dont think I would want that! (It would only be a simple mod to add another switch neway!)


ANYWAY :wink: Ill finally get to the point!! I plan to use RGs panning for fun circuit to mix the signals BUT i cant work out what the end part of the circuit does!!! :wink:  

Can you guys help? :wink:


Cheers,
Ally

http://uk.briefcase.yahoo.com/toad_boy1983/

Go to the schematics folder, picture file is called "WTF is it?"

[Paul Perry (Frostwave)]

That circuit fragment looks like a transistor amplifier with gain of 5 or so, and some top end rolloff. Plus heavy decoupling of the power supply.

[AllyP]

Could you possibly explain that in idiot terms :wink: !!

Transistor amp I get....How do you work out the gain?

Which part rolls of the top end?  

What is decoupling of the power supply?  what does that do?  What bits do that?

Sorry for all the questions but this board is my sole source of electronics lessons I find it very interesting!!


Thanks again,

Ally

[Andreas]

As I'm a beginner, too, this might be a good way to test my understanding of what's going on there. So, please don't regard this as a valid answer to your question but rather a rough guess which I like to check against someone else's better knowledge.

The gain: Should be about the ratio of Rcollector / Remitter. This would rather be between 6 and 7, so there might be some "dirty effects" of the bipolar transistor, which I did not take into account.

Top end rolloff: The 250 pF cap from the collector to the base provides some negative feedback and thus dampens the amplification. But as it's quite a small cap, it only let's high frequencies through, so the low end isn't dampend that much.

Decoupling of the power supply: I guess this refers to the big caps on the top of the schematic, which help to keep the voltage constant and reduce cross effects between this stage and the other stages.

[AllyP]

SO do I need this section at the end?

I will clearly need to keep the decoupling caps to regulate the psu

I will have to add an Opamp anyway for the panning part of the circuit....should I just add a TL072 and use the spare opamp as a gain 5  amp?