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The Effect Builders Club!

#281
chicago_mike said:
I just etched 8 boards tonight. Super easy and simple process too. I use the muriatic acid / hydrogen peroxide method. very easy to use too.

The next batches will include the pedal version of the interstellar overdrive that I have been talking about making. Its going to be a cool idea, as long as she works.:)

Might even turn this into a business. Its actually kinda fun to be this geeky.:bassist:
Click to expand...

Hm, I actually used the ferral chloride way, which honestly I'm not sure I like. What is your process for the muriatic acid?
 
#282
Hey nifty: I've got a question for ya!

in that octave fuzz kit that guy posted a link to, you can get to the pdf which has the circuit diagram, in case you didn't take the time to find it, I attached it.

In the schematic, they have R5 going to ground, and right next to it, using the same node, they have R6 and C4 going to ground. Using the electrical engineering principles I learned in school this past year, theoretically, we can replace those two resistors and capacitor with a 224.3 ohm resistor and a .001002uF cap in series, to ground.

Now why would they do it this way when what I said would be equivalent, or more importantly, it is so close to the 220 ohm resistor and .001uF cap, that I doubt there is a noticable difference!

So do I have something wrong or could this circuit be simplified slightly?

also if R6, which looks like it says 220R really says 220k, then the resistor and capacitor should be 110kO and .004uF

an easier way to explain what I say it should be changed to would be to say R5 is now gone, and R6 = 224.3 ohms and C4 = .001002uF (or with my second situation, R6 = 110kO and C4 = .004uF)

I attached the pdf with the circuit in it, it is the last page.
 

Attachments

#283
Sir Edward V said:
Hey nifty: I've got a question for ya!

in that octave fuzz kit that guy posted a link to, you can get to the pdf which has the circuit diagram, in case you didn't take the time to find it, I attached it.

In the schematic, they have R5 going to ground, and right next to it, using the same node, they have R6 and C4 going to ground. Using the electrical engineering principles I learned in school this past year, theoretically, we can replace those two resistors and capacitor with a 224.3 ohm resistor and a .001002uF cap in series, to ground.

Now why would they do it this way when what I said would be equivalent, or more importantly, it is so close to the 220 ohm resistor and .001uF cap, that I doubt there is a noticable difference!

So do I have something wrong or could this circuit be simplified slightly?

also if R6, which looks like it says 220R really says 220k, then the resistor and capacitor should be 110kO and .004uF

an easier way to explain what I say it should be changed to would be to say R5 is now gone, and R6 = 224.3 ohms and C4 = .001002uF (or with my second situation, R6 = 110kO and C4 = .004uF)

I attached the pdf with the circuit in it, it is the last page.
Click to expand...

Hm, this is a tricky one, but I'm pretty sure they have to be seperate. I think the difference is that R5 is connected to the collector of the transistor acting as an amplifier. I could be wrong as my transistor theory needs a lot of studying.
 
#284
A capacitor is a DC open circuit, so if you replaced R5, R6 and C4 with just a resistor and cap in series, then the presence of the cap would prevent a DC ground path in that area of the circuit. This would affect the biasing of Q1. So, R5 provides a DC ground path for the biasing voltage for Q1, while R6 and C4 provide filtering.
 
#285
niftydog said:
A capacitor is a DC open circuit, so if you replaced R5, R6 and C4 with just a resistor and cap in series, then the presence of the cap would prevent a DC ground path in that area of the circuit. This would affect the biasing of Q1. So, R5 provides a DC ground path for the biasing voltage for Q1, while R6 and C4 provide filtering.
Click to expand...

ooooh I get it.

So if it only operated on AC voltages, what I said would be ok, but this little addition allows for different operation for DC.

I was thinking solely in the AC world.

Side note: I have no idea how transistors work.
 
#286
Well, it's not so much that it operates at DC - but to get the transistor to do the right thing it needs to be biased, and biasing is done using DC voltages.

An AC signal has positive and negative voltages, but a transistor can only reproduce positive voltages. So you have to offset the signal with a positive DC voltage so that the AC signal then has positive and 'not-so-positive-but-not-negative' voltages instead.

...if that makes any sense!

Google for some basic tutorials on class A amplifiers - that is essentially what you're looking at.
 
#287
niftydog said:
Well, it's not so much that it operates at DC - but to get the transistor to do the right thing it needs to be biased, and biasing is done using DC voltages.

An AC signal has positive and negative voltages, but a transistor can only reproduce positive voltages. So you have to offset the signal with a positive DC voltage so that the AC signal then has positive and 'not-so-positive-but-not-negative' voltages instead.

...if that makes any sense!

Google for some basic tutorials on class A amplifiers - that is essentially what you're looking at.
Click to expand...

Yeah, this is what I was thinking. Thank you for the help. For some reason my course work has only taken me through intro to transistor(DC circuit analysis) then went to logic circuits with the ideal transistor.

I think I would rather know how it works, but who knows. :)
 
#288
niftydog said:
Well, it's not so much that it operates at DC - but to get the transistor to do the right thing it needs to be biased, and biasing is done using DC voltages.

An AC signal has positive and negative voltages, but a transistor can only reproduce positive voltages. So you have to offset the signal with a positive DC voltage so that the AC signal then has positive and 'not-so-positive-but-not-negative' voltages instead.

...if that makes any sense!

Google for some basic tutorials on class A amplifiers - that is essentially what you're looking at.
Click to expand...

Don't worry, you made sense.

I should learn how transistors work...
 
#290
niftydog said:
It was a red letter day for me! But it really takes a bit of reading before you find an explanation that makes you go "ohhh yeah, duhh!"
Click to expand...

I kinda know some basics on like... HOW it works physically, but I don't really know how to use it or anything... maybe if I thought about it for a little while... but then again, the way I think it works would make two of the pins identical, so I am probably missing something.
 
#296
Sir Edward V said:
How many pins come out from a transformer that you can buy?

Want to just give a general synopsis on how to hook up a transformer?

I have several questions, haha

I want to know all about everything, in case you can't tell yet!
Click to expand...

Ok, I looked at the pinout of a transformer, and your right, there usually is only one ground. Again, I think it is just telling you to ground it.

So you can think of a transformer as basically two coils of wire. Now, the voltage between the two coils is described mathematically as

V2/V1=N2/N1 Where V=voltage, N=number of turns in the inductor, 2=secondary coil, 1=primary. So by the equation, if a coil has less turns, it will have less of a voltage. Basically, a transformer can step up or down a voltage.

To connect them, you link you positive V to one side of the coil and your negative(ground) on the other side. Same with the second coil.

Here is a picture that illistrates it pretty well.
350px-Transformer3d_col3.svg.png


More info here. http://en.wikipedia.org/wiki/Transformer

If you have any other questions, feel free to ask.
 
#297
Sir Edward V said:
...the way I think it works would make two of the pins identical, so I am probably missing something.
Click to expand...
That sounds more like a FET kind of concept - drain and source can be thought of as interchangeable - but it's not the case with a BJT.

Think of the path from collector to emitter as a big fire hose - the base is like the handle of a valve installed in the fire hose. There's no way you could hold your hand over the end of the fire hose and stop the water coming out, but the valve enables you to easily stop the flow with a simple flick of the wrist.

Hence, a small base current can control a much much larger collector current.

Sir Edward V said:
oh and what is the deal with that transformer in the octave fuzz schematic that has a line/wire coming out from the right side going to ground? is it a variable transformer or something?
Click to expand...
That's called a coil tap - essentially it gives you two secondary coils instead of just one. By hooking them up in this way you actually increase the voltage that the diodes see - probably helps compensate for the loss of volume due to the rectification process.

Sir Edward V said:
Want to just give a general synopsis on how to hook up a transformer?
Click to expand...
Think of a simple scenario you want to know about and I'll talk you through it. There's hundreds of ways to use transformers and hundreds of different transformer configurations so it's a bit hard to do in a few sentences!
 
#298
niftydog said:
That sounds more like a FET kind of concept - drain and source can be thought of as interchangeable - but it's not the case with a BJT.

Think of the path from collector to emitter as a big fire hose - the base is like the handle of a valve installed in the fire hose. There's no way you could hold your hand over the end of the fire hose and stop the water coming out, but the valve enables you to easily stop the flow with a simple flick of the wrist.

Hence, a small base current can control a much much larger collector current.
Click to expand...

I don't know which are collector or emitter or base... :D

niftydog said:
That's called a coil tap - essentially it gives you two secondary coils instead of just one. By hooking them up in this way you actually increase the voltage that the diodes see - probably helps compensate for the loss of volume due to the rectification process.
Click to expand...

hmmm, odd... so is it adjustable, or does it just connect in the one spot?

niftydog said:
Think of a simple scenario you want to know about and I'll talk you through it. There's hundreds of ways to use transformers and hundreds of different transformer configurations so it's a bit hard to do in a few sentences!
Click to expand...

I really can't think of a use...

I learned a little bit about them in school, I know how to apply them to AC circuit analysis to transform impedances... something along those lines. I know about the turns ratios and how it transforms Voltages, current and impedances... I think! haha
 
#299
The emitter has the arrow, the base is the horizontal pin on the left, the collector is the left-over one!

Transformer taps are fixed, non-adjustable.

The main purpose of a transformer for our purposes is to transform voltages, so if you understand how that relates to the turns ratio then you understand 90% of what you'll probably ever need to know.
 

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