can someone tell me how to combine these 2 effects into one box?

[ljoe1969]

Hi.

how can i combine these two effects to use the same battery etc....

effects used seperately sound good to me built into seperate boxes.

i want to go from guitar to distortion to clean boost. can this be done and work properly. i already tried connecting output from distortion to input of clean boost as is. it just doesn't sound the same as when they are in different boxes.

any help would be appreciated.

joe

[euronymous0001]

1) are there any modifications made to the circuit (both dist and boost) to the 2 separate boxes?

2) what was the difference in the sound you were referring to?

[Mark Hammer]

Here is the schematic for the Voodoo Labs Overdrive - http://gaussmarkov.net/layouts/vlo/vlo-schem.png.  You will notice that, while the gain structure is a little different than yours, it is pretty much the same thing: An op-amp-based diode clipping stage, followed by an op-amp gain stage.

You can see that, rather than a fixed gain in the clipping stage, there is a pot to vary the gain, and how much clipping is produced by the diodes.

What you can also see is that, rather than the dual 2M2 resistors used in each stage to centre the signal on a 4.5V reference voltage, a pair of 47k resistors are used to produce Vref and the relevant points in the circuit are tied to that.

IC1b is a gain recovery stage set to a gain of of around 4x.  That helps compensate for the way that the clipping diodes limit the output.  It also means that one can still get a pretty hot output (7.8x) even if you set the first stage for minimum gain.

If you were to build this circuit, and run a "side-circuit" in parallel with R9, you might have what you're looking for.  The gain of IC1b is set by both R9 and R8, but since changing R8 might require a different value of C5, we'll just tinker with R9.

If one were to place a 100k resistor in parallel with R9, that combined parallel resistance would be just under 32k, which would make the gain 5.7x, instead of 4.2.  If we were to make that 100k resistor a pot instead, then we could make the combined parallel resistance even lower, which would increase the gain even further.

Now, you need to have some resistance in there to prevent chip misbehaviour, so you don't want to be able to use the pot to provide a zero ohms bypass around R9, so let's prevent that, by sticking a 22k resistor in series with the pot.  That will make the lowest it can go 22k, such that the gain of IC1b with those extra parts will max out at 11x, instead of the stock 4.2x.  That's a pretty big boost.

Now, if that 100k+22k parallel path had to go through a switch to connect around R9, turning the switch on and off would produce a preset gain change and boost, determined by the value of the pot.  If the pot is set to maximum resistance, then the gain set by their combination of R9 and the two extra components would be 5.4, amodest boost, but one you would notice, since it is mutiplied by whatever the gain/output of IC1a is.  Turn that 100k pot down to minimum resistance, and you get a boost of 11x.  Remember that even if IC1a is set to minimum gain (no clipping), the extra boost available from IC1b could give you an overall combined "clean" gain of 20.5x, which will punish the input of any amp.

Long story short, if you were to build this circuit (and the gaussmarkov page will show you how), and add a switchable parallel resistance path around R9, that will get you a very pleasing overdrive tone, plus a healthy volume boost when you want it.  Since the boost only needs a simple SPST to enable/disable, you could easily build this into a 1590BB (with the long side facing you so you can keep the switches far apart), using a 3PDT to bypass the entire pedal, and a DPDT to actuate the boost and turn on an indicator LED to let you know its on.