Forgive me for posting this REALLY embarrasing question :(

[rockgardenlove]

So, on the easy drive, how would you add a gain control?

(Sorry, really nooby )

[twabelljr]

I'm not sure either, but lets try to figure it out.

What part of the circuit does the gain come from?

What components set the gain?

What can we change or add to be able to reduce or increase this?

I'm gonna do some research. Lets's see who can figure it out on thier own. I'll be glad to help once I get the answer!

[rockgardenlove]

I'd lean towards putting a pot on the 22 uF cap...but only because I've seen it on other pedals...don't understand why really.  Could someone explain why, if this is the case?




For volume you would just add a pot to the collector of the tranny right?  Maybe?  Or should I add it onto the end.


Thanks!

[twabelljr]

Introduction
This circuit is a simple one-transistor wonder that wrings a decent amount of fuzz and tone from some spare parts you probably already have. No special germanium transistors are required to get a classic tone. And it will go from clean to dirty with a flick of the guitar volume.

Circuit Notes
Use a high-gain transistor for best performance. None of the part values are critical, so close-enough values will probably work. As shown there are no gain/volume controls, but those are easily added before and after the circuit. Standard 250k audio tapers should suffice.

The gain seems to determined by the input level. (guitar volume) It can be decreased, but how do we increase it?

[ulysses]

you would prob need to use a single opamp somewhere to increase the volume.

cheers

[bass_econo]

Wouldn't adding a larger cap on the input increase the input, therefore increase the gain? A little anyway, I would think.   Also I would think that lowering the value of the resistor on the emitter would do that as well.  A volume pot would go after the cap on the output. 
Now I'm a noob as well so take this with a grain of salt.

[toneman]

how bout an adjustable-gain MOSFET or JFET preamp 

does the 22mfd determine gain 

[Jeremy]

The gain seems to determined by the input level. (guitar volume) It can be decreased, but how do we increase it?

That's right; the gain right now looks to me like it is at max for this circuit.  You can decrease the amount of distortion by putting a simple level control in front of everything, which would do the same thing as turning your guitar down, or you can change the 680 ohm resistor on the emitter into a 1k pot and attach the 22 microfarad capacitor to its wiper.  

On the other hand, if you changed the 680 ohm resistor into a 1k pot, when you turn the gain down with the pot, the input impedance of the circuit will rise, which will let more of the original signal through, so that might give you some weird results.  Not necessarily bad, but I haven't done the math to figure out just what it would do.

This will not be a problem if the signal coming into the effect is low impedance signal, like if it's coming from an effect with a buffered output, or an active pickup.  Or, you can build a simple buffer into the input of this circuit.  But then you're using two transistors instead of one, which ruins part of the novelty of having a one-transistor distortion!

[twabelljr]

The input cap keeps DC current from getting into the guitar, and the value determines the frequency that gets let into the circuit. Larger cap = lower freqency. Maybe a pot in series with the 680 ohm resistor off the emitter will control it. The 680 may need to be adjusted accordingly.

[cd]

The input cap keeps DC current from getting into the guitar, and the value determines the frequency that gets let into the circuit. Larger cap = lower freqency. Maybe a pot in series with the 680 ohm resistor off the emitter will control it. The 680 may need to be adjusted accordingly.

If you don't want to change the frequency response, that's the way to do it.

[twabelljr]

Thanks CD. Can you explain what this does to the transistor to affect the gain, and will this only decrease the effect. Is it set for max. gain or will resistor values allow an increase? Most detailed explanations are for 2 transistor fuzz circuits that I can find tonight. I like trying to help solve peoples questions, I learn in the process. I'm gonna read some more.

I'd lean towards putting a pot on the 22 uF cap...but only because I've seen it on other pedals...don't understand why really.  Could someone explain why, if this is the case?

You had it RGL.

[rockgardenlove]

Alright then, so WHY does that 22 uF cap do anything?

[Jeremy]

The 22uF cap shorts AC signal to ground, which increases the gain to the guitar signal while leaving the DC bias point alone.

Putting a pot in series with the 680 ohm resistor would not affect the guitar signal much, but it will screw up your DC bias. 

Putting a pot in series with the 22uF cap will affect your gain.  That's a possible solution.

[cd]

Alright then, so WHY does that 22 uF cap do anything?

Bypassing the emitter resistor increases gain.  Read these:

http://www.williamson-labs.com/480_xtor.htm
http://www.rason.org/Projects/bipolamp/bipolamp.htm
http://www.kpsec.freeuk.com/trancirc.htm
http://users.tpg.com.au/users/ldbutler/TransisVoltAmp.htm

[MrChameleon]

Here's your answer ...

http://www.indyguitarist.com/torchy/Distortion_Overdrive/JD%20Easydrive/easydrive%20with%20knobs%20on_sch.gif

I've buit the (no knobs version) EasyDrive and it's great! Very sensitive to picking/fingering style and to pickup volume and type.

PS. Thanks to Joe for the schems, to Torchy for Vero layouts, and to indyguitarist.com for hosting them.

[rockgardenlove]

Sweet! 

Where can I find a very layout?

[smnm]

I help (image from http://www.indyguitarist.com/torchy/)

[rockgardenlove]

Awesome, thanks!