I hate math

[PRR]

> got me better

I sense that you don't have a grasp.

Not sure how much "math" is hindering you.

Let's try one-finger math.

First: skip all the caps. We can't deal with audio until we get the transistor set-up at a happy DC condition.

Assume 10V supply.

We want the collector resistor dropping a lot of this. "Half" is good.

Transistor base-emitter voltage is about 1 Volt. (It will really be 0.5V-0.7V, but let's avoid tricky math.)

We need an emitter resistor to drop a voltage "not small" compared to transistor base-emitter voltage. 1V is enough.

So far we have 10V supply, collector at 5V, emitter at 1V. We have lots of room (10V-1V) to swing the collector, the output terminal. We waste only 1V in emitter bias.

Remember these relative proportions! Collector resistor and collector-emitter drop most of the available voltage. Emitter resistor voltage is smaller.

How does the emitter know to be at 1V? We force the base so that 1V appears at emitter. We already pretended the base-emitter voltage drop is 1V. Therefore the base must be forced to 1V+1V=2V.

We could use a 2V battery, but not handy; we will also eventually mix audio here and a battery would absorb audio.

We use a voltage divider. Be familiar with the concept.

Pick a collector current. Often 1mA is as good as anything.

Emitter current is the same as collector current.

Now we can pick collector and emitter resistors.

We need to pick a current to flow in the voltage divider. Too small won't force base voltage firmly enough. Too high will lead to small resistors which will absorb the signal we will add later. When you don't know better, pick divider current 1/10th of collector current. 1/10th of 1mA is 0.1mA.

[arawn]

wow I got the book Guess i have some reading to do. I been working from "Electronics Demystified" and aside from an emitter bypass cap this is what they say a common emitter should look like. I truly appreciate everyone's assistance, happy accident i guess, i have this on a breadboard and aside from wanting more gain it does work.

[PRR]

> it's not really a common emitter circuit at all.

Each stage looks common-emitter to me. Might be "more pure" with emitter resistor bypass, but BJTs often need significant resistance there to tame them. Input base-to-emitter, output collector-to-emitter.... emitter is the common node.

Of course until the DC conditions bring the transistor half-way between off and on, it isn't a linear amplifier.

[Projectile]

> it's not really a common emitter circuit at all.

Each stage looks common-emitter to me. Might be "more pure" with emitter resistor bypass, but BJTs often need significant resistance there to tame them. Input base-to-emitter, output collector-to-emitter.... emitter is the common node.

Of course until the DC conditions bring the transistor half-way between off and on, it isn't a linear amplifier.

Did some research and it appears this is correct. I thought the definition of a common emitter amplifier was more narrow. My bad.

[Projectile]

[deleted] double post

[arawn]

Okay i now have a working circuit that sounds pretty good into my tube amp. No diodes just overdriven input and transistors. Mr Hammers stupidly wonderful tone control and volume so just 2 knobs but so far a ton of great sounds and for your approval I have dubbed this De El Diablo. I am next going to work on perf and pcb layouts (sorry kids I don't do vero). Much thanks got to RG and PRR for helping me get some kind of hold on the math.

[PRR]

What do the 1K resistors off the collectors do? What changes if you replace them with shorts?

[WGTP]

I doubt this helps, but Math is easier than Human Behavior to figure out. 

[arawn]

To be honest PRR I am not sure. I may try it i am playing on this thing again tonite!

[arawn]

okay added a high pass in between the first and second stages

[arawn]

Prr I pulled the emitter resistors and sent them straight to ground. All of my voltages dropped by a .1 or so, but more to the point the amount of distortion increased at least to my ears.

[PRR]

> I pulled the emitter resistors

I asked about the 1K resistors off the collectors.

Taking 1K out from under the emitters will increase gain; and thus clip sooner.

However the 1K resistors off the collectors are, for audio, in-series with the 10K collector resistance. And 10K = 11K for many practical purposes. And being lazy, _I_ hate excess parts.

[arawn]

you are correct sir it was in fact the collectors that i removed the 1k resistors from. and yet in spite of my incompetence it is starting to sound really good .

[arawn]

soundclip http://soundcloud.com/arawngwydion/deeldiablo
I apologize the guitar needed strings when i recorded that and I am not set up for mic'ed recording at this time so this is direct through my rp80 on bypass.

[Projectile]

Ouch. Sorry man, I hate to say this but that sounds absolutely terrible. Just awful.

[arawn]

Yeah it's the recording, I can't do quality