Hi. I'm new to this forum, and a beginner with effects building. I've spent several months just reading info here and at the geofx site, and everywhere else I can find it, and building very small test circuits with single transitors and diodes. During my many hours spent just studying schems, I've hit problems in understanding that I could not find the answer to in the FAQ or anywhere else. I apologize if these are stupid questions, I just want to understand how these circuits work and not just how to build them. I will only ask one question at a time, since undestanding the answer to one question very well could give me the understanding for my other questions, and I don't want to load down the forum with bad questions.

Coming from a computer programmers mindset, I find many things common in the thinking between EE and programming. I trace through the schems following the paths of the signal, trying to undestand the workings of them. My biggest question I have not found an answer to involves transistors. My understanding of transistors from a digital POV was, you had input on the C, output on the E, and you pump current to B to get them to connect together like a switch. My understanding thus is, flow to C, current to B, flow out on E.

However, in several schems I see cases where the emitter of a trans is simply dumped to ground. The C is connected to both the V source and also to the B of a second transistor, such as in the FF schem. How in the world is the first transistor doing anything at all to the signal in terms of amplification if you are dumping the output to ground? Am I missing something in the way the current flows in the circuit?

My second question is similar in terms of diode clipping circuit bing attached to ground, but I figure if I understand the main problem in the case of a transistor to ground, it will also answer that too.

Sorry, sticking this in the Beginners thread, I didn't know what that was for before I posted.

FF Q1 emitter to ground, signal goes to Q2 base from Q1 "Collector"...
 Q2Collector goes to Q2R then to output cap, outputs come from the collectors.

ok, your next step, if you are as keen as you appear to be, is to read some articles like this to give you greater understanding of transistors.

I will give you a bit of a guide of common emitter amps, there are other configurations of amplifiers and this may the source of some confusion for you at this stage.

common emitter amps have a signal input at the base. They have the power supply connected and the collector. The emitter is usually grounded for AC signals, and sometimes the emitter plays a part in the biasing (which is related to the DC conditions of the amplifier.)

When the transistor is turned on, current flows from the power supply, via the collector and out the emitter. This current flow creates a voltage drop across the collector resistor, resulting in the voltage at the collector itself changing from what it was during the "off" state.

Transistors are turned on and off in proportion to the current flowing into the base. The base will only require a tiny amount of current in order to switch on - but it will allow you to control a much larger amount of current flowing through the collector-emitter. The difference between the small base current and the large collector current depends on a parameter called Beta which is sometime refered to as the current gain. This is how we acheive amplification.

In a class A amplifier, the base is biased so that some collector current is flowing all of the time. This allows us to either increase or decrease the collector current (not just simply turning it on or off) by applying either a positive or negative voltage at the base. Thus, the voltage at the collector can be increased or decreased around a central point.

Now, are you getting the idea of what comes next? Of course, connecting an AC signal at the base will now produce a varying voltage at the collector that represents the input signal, but larger in amplitude.

To answer the other question would require me to be familiar with the fuzzface, which I am not. There are plenty of resident experts who might shed some light on that for you. Suffice to say it sounds as if you're talking about a "darlington" configuration, which is a way of making a very high gain (large Beta) transistor out of two discrete, small gain transistors. This is covered in the article I linked to above.

Diodes are also covered in that series of articles, but to prod you in the right direction think about this; Diodes only conduct in one direction - but audio signal can be both positive and negative. Also, keep in mind that diodes require 0.7V bias before they "turn on". Keep a signal at 0.8V peak and most of it remains unaffected by the diode action...

food for thought.  

This might help some:

http://www.geofex.com/Article_Folders/fuzzface/fffram.htm

Quote from: niftydog
When the transistor is turned on, current flows from the power supply, via the collector and out the emitter. This current flow creates a voltage drop across the collector resistor, resulting in the voltage at the collector itself changing from what it was during the "off" state.

Thank you. This answered my question very nicely, I do understand now. Basically, you aren't using the 'output' like I'm thinking as in regular DC circuits, we are using the changes in voltage to C due to the signal at B to modify the input of pure DC from our V source in the circuit to appear like a bigger version of the signal, and the 'output' on E isn't useful (which explains why my tests of hooking up E to the output line caused intermittant crackling). I understand how this works now and why its hooked up that way. This also does explain the clipping circuit to ground as well. Thank you very much again.