Crunch Box, regular VS v2

[ozzu2000]

Hi!
I'm looking for a schematic to build the crunch box, but I seem to find 2 versions  of it, one has a fixed presence seting, and the other has a presence pot and other minor tweaks.
(will post the schematics soon)
I'm leaned towards the V2 but I have some question:
1. Which one of them is the same as the original MI crunch box? I thought the "regular" schematic, but it doesn't have a presence trim.
2. Do the mods on the V2 make is sound diferent from the "regular" one? It has some diferent caps...
3. Other than adding the presence pot, what do the other changes on the V2 do?

Thanks

Schematics (regular)


Schematic (V2)


PS: this schematic appears on this topic below, but doesnt explain much...
http://www.diystompboxes.com/smfforum/index.php?topic=70950.0

[WGTP]

The 470 ohm resistor will drive the LED clippers a little harder.  The trim pot will allow you to adjust the range/action of the tone control.  The 470 ohm resistor may be making up for additional loose caused by the tone control changes. 

[ozzu2000]

I'm having an interpretation problem with this layout, in the tone section.
Aren't tone pots usually connected like this?:

[Seljer]

Both are valid ways of making a tone control. The ProCo Rat's tonecontrol is implemented as the prior schematic.

Both are just an RC lowpass filter, http://www.muzique.com/schem/filter.htm . In one you're changing the actual R part of the filter, in the other you're putting extra resistance inline with the capacitance and kind of 'lowering' the C part

[ozzu2000]

With the arrangement in the original schematic, wont the volume change a lot with diferent tone settings? Maybe I'm not understanding the principle behind it

So, just to be sure, the wiring on the original schematic is like this right?

[earthtonesaudio]

Yes, the volume will change with different tone settings.  But whether or not it changes "a lot" depends on the input impedance of the next device and the setting of the volume pot.

For instance if the amp input impedance is 10k (unlikely, this is extremely low just for illustration purposes), AND the output volume control is set to 100%, then changing the tone control setting may reduce the output voltage by 1/2, or about 6dB.  This is not a "LOT" but certainly noticeable.  However in this same scenario if the output volume control is set to 3/4 of maximum, then the maximum difference you will get with different tone settings is about 2dB, which is just barely noticeable.

With higher (more typical) impedance loads this effect is minimized even further.

[WGTP]

The Rat Style provides a 6db/oct. roll off.  The other is more a shelving control, but can sound the same depending on where the roll off occurs.  

Sims with LT Spice show that the 2 separate tone controls are not really separate and they blend together.  They do not produce a 12db/oct roll off as originally thought.  That doesn't mean you won't get some different EQ with them. 

[StereoKills]

So, just to be sure, the wiring on the original schematic is like this right?

I think you want to tie the right side of the pot to the wiper in the diagram.