easydrive unintentional mods ?

[electrobuster]

hello stompfiends,
I am new to this addiction and I am not sure this is the right index for my question but here goes.
Joes Easydrive is my 4th build and the first just using the schematic. After playing with it and enjoying the sound and tone this little gem produces I thought it might be good to add the volume and gain pots.
As you can imagine being new to this "black art" of electronics I found this challenging. I managed to get the vol pot working but I'm not sure if I did this correctly as I ended up omitting and removing the 0.1uf cap(input cap?) that runs to the diodes and collector.( see GGG layout which I later used as a reference)
Also in trying to get the gain pot working(which I ended up leaving out as I am too nooob)  I removed the 680k resister and decided to leave it out. This produced more gain and a real sweet spot response from the guitar.
I'm slowly getting my head around this stuff and starting to understand what the components do but I am not sure if these changes are detrimental to the circuit or my amp.
At this stage any simple advice would be helpfull, thanks in advance

[electrobuster]

http://www.generalguitargadgets.com/diagrams/joesodpe.gif

here is the link to the layout I ended up using as a reference.
The schem I built from is the Analogalchemy one hosted here

http://www.diystompboxes.com/pedals/index2.html

[brett]

Hi.
The simple one first:
This circuit has the emitter biased up off ground by that 680 ohm resistor.  (I *think* you meant that you took out the 680 OHM resistor, right??).  The base is always 0.7V higher than the emitter, so it's sitting at 0.7V plus the voltage across the 680 resistor.  Taking that resistor out will drop the base and collector voltages quite a bit.  In fact, the output signal is probably going to "bottom out" more often.  It doesn't have much room to move in a negative way.  The same thing happens at Q1 of a Fuzzface, and is an important part of its famous sound.  Maybe you should call this the FuzzDrive!! (The EasyFace is already taken).  Cool mod.

I can't quite work out in my head what the deal is with that 0.1 cap.  It will make one of the diodes conduct most of the time.  Interesting idea.  You might like to compare what you've got with the Bazz Fuss.

cheers

[brett]

PS if you take the 680 ohm resistor out, you can take the 22uF cap out, too.  This is too simple...

[electrobuster]

Thanks for the reply Brett,
Thats right I removed the resister, but it was a 680k not ohm.
as the schem just said 680 I asumed it to be "k" not ohm. Maybe I will build it again with the correct resister.
Learning more every day

[brian wenz]

Hello Hello--
    Mmmmm........if it doesn't say "K" then it's supposed to be ohms.
Brian.

[electrobuster]

OK I just tried it using a 680ohm just to see the difference with the intended resitor range.
But I took it out and also removed the 22uf cap as Brett sugested.
So I guess its an even easier drive.
It sounds super smooth with nice octave up overtones using the neck PU.
Maybe soon I will actually understand what I'm doing, but I am pleased with my ignorant hack effort. I will right this off as dumb nooob happy accident.It works for me

[z-zero]

I believe in the circuit notes on Joe D's page it explains the cap in between the collector and base. I think its there to isolate the diodes from DC so it doesn't affect the gain of the transistor. His goal after all was to get the most gain from a single tranny. Lots of things to play with for such a simple circuit, one of my favorites.

z-zero

Here is what he says exactly:

Diode Clipping: Two back-to-back diodes and a capacitor make up the clipping section. The .1µF capacitor blocks DC, and allows the diodes to perform clipping on AC signals without interfering with the transistor bias. Diodes have a slight curve (or "knee") as they go into conduction, rounding off the sharp edges of the resulting square-wave.