MXR cascade mod

[jkup84]

I've got an MXR Doubleshot that I'd like to mod so the effect on/off switch becomes a cascade on/off switch. I'd like to leave the existing A/B switch as it is because I switch between A and B frequently. I don't have much experience with electronics, but I can run a soldering iron pretty decently.

--JKup

[jkup84]

Also, does it make a difference if the cascade is series or parallel?

[Mark Hammer]

"Cascade" implies series.  Parallel would be relevant if you had some means of mixing the two distortion sections together, but my understanding is that the Doubleshot does not have that capability on its own.  To parallel them, you would likely need to fit stuff in there which probably won't fit.

Can you cascade the two sections in series?  Probably, though from their description I'm not sure that you'd gain much.  On the other hand, when did you NOT hear a pedal described as delivering "searing, over-the-top distortion", no matter how limp-wristed it may be?  So, without having heard one in action, I'll give you the benefit of the doubt and accept that maybe there is something to mine with respect to series wiring.

The key here will likely be to either forfeit the channel switching capability, or install a toggle somewhere.  Now, what exactly is possible?

The manual indicates that the stompswitch on the right selects between the two channels.  Note that since these ARE two channels, rather than simply normal and boost, the channel switch has to do something more complex than simply shunt a gain-setting resistor or something equally bone-headed.

The ideal would be if it is a 3PDT mechanical switch that completely pulls one channel out of circuit when it inserts the other one in circuit (I say 3PDT because I see there are channel indicator LEDs), coupled with a "normal" 3PDT true bypass stomp;switch for the effect/bypass function on the left.

*IF* it were wired like that, it would be a fairly simple matter to do the following:

1) Identify the two leads from the rightside/channel switch that go to the input and output pads of each of the respective channels.
2) Identify the "send" and "return" lugs of the leftside/effect stompswitch.
3) Figure out which channel you want as the "default effect" and which one you want as the add-on series channel.  Unsolder the connections for the default channel from the rightside/channel switch and replace tyem with a straight wire link between those lugs.
4) Route the "send" line of the effect/bypass switch to the input pad of the "default" channel.
5) Route the output of the "default" channel to the "input" of the rightside channel switch, which will now become a single-channel/two-in-line switch.  Note that my plan forfeits channel swapping, and that the moment you engage the leftside switch you will always have the "default" channel, and will use the rightside switch to make the sound/distortion more and less intense by adding/omitting the second channel.

Okay, what do you have at this point?  The left switch turns on the entire unit or bypasses it.  When it's on, the default channel is always engaged, no matter what else you do.  You can set that channel for its most intense, or you can set it for a little colorated rhythm sound, etc.  When the rightside switch is engaged, although the LED will indicate that the other channel is now on, it will in fact add the second channel AFTER the first one so that you essentially have two distortion units in series.

Note the following:

a) Any amount of gain in stage 1 in MULIPLIES with any gain in stage 2, such that a gain of 100 in stage 2, with a gain of 2 in the first stage equals an effective gain of 200 for the second stage (I'm assuming here that there is some sort of traditional boost-the-diode-clip deal in effect).  You will need to re-educate yourself with respect to level setting in the stages.

b) You will gain the added advantage of being able to introduce pre-clip EQ by setting stage 1 for unity or similar gain and tweaking the EQ controls.  This will not produce "more" distortion overall, but can mimic things like setting a wah in a fixed position, Billy Gibbons style gronkiness, or other types of biases in what clips most and least.

Now, if the switching scheme is one that LOOKS mechanical on the outside, but is actually FET-based onthe inside, disregard what I wrote.  All bets are off.

[Phorhas]

HEY jkup84

Could you by any chance post pics of the bouble shot guts? -board, trace side and off board wiring?

it's quite interesting


thanx ahead

Dan.

[jkup84]

I'll see if I can dig up a camera today. I might have pics by this afternoon or tomorrow.

--Jeremy

[jkup84]

ok...so now that I have some pictures, does anyone know how to post them?

--J

[jkup84]

Right. Forget that last post. I finally had some time to read the intro information, so I consider my photo question answered.

--J

[cd]

I have a feeling we're going to see SMD components, which basically means "fuggedaboutit"!