RambleFX Marvel Drive 1.0

[PedalBlotter]

The Ramble FX Marvel Drive is a nice sounding Plexi Pedal with parallel blending inputs, like a real amp.
It  sounds amazing !!, i have one here  (V1.0) borrowed and make a schematic.
That´s the first time i analyze a pedal and make a schematic.
So consider me, and check the schematic, if there are any errors in it.
If someone can make a verolayout, that would be great



Download this schematic

[Frank_NH]

Indeed - the online demos of this pedal are just amazing!  This one is definitely on my build list...

Check it out:

Marvel Drive Demo

BTW - you may want to move this to the Request category...

[PedalBlotter]

Mark can move it

[IvIark]

Yes I'll check this one out

[IvIark]

There seems to be a few problems with the schematic.  Most of the JFETs gates are either grounded directly or via a resistor, I think there is a bit of a mix up between the gate a source pins in some of them.

[PedalBlotter]

Yeah i think i mistaken source and gate in the schematic

[PedalBlotter]

Ok i changed it.

How does it looks now ?

[Frank_NH]

My (somewhat noobish) take on the schematic:

(1) "CE" caps below R820 - odd parallel configuration.
(2) Should there be a coupling cap at the input?
(3) The double 50K/2.2nF cap arrangement at the output.  I suppose that's a second order low pass filter?
(4) Q3 looks odd...should there be a connection of the drain to +9v?

Are there pictures of the PCB?  That would help...

Good luck and I hope this gets sorted soon

[PedalBlotter]

Don´t know, just followed the circuit path with my multimeter.
I´ll check that again.
It´s a double pcb....

Pictures:

[PedalBlotter]

I checked this again:
"My (somewhat noobish) take on the schematic:"

"(1) "CE" caps below R820 - odd parallel configuration."

Yes, from R820 to +220uf and to +100uf cap.
But there was a ground false there (820R), i fixed it.

"(2) Should there be a coupling cap at the input? "

No, input goes straight to the 33k´s


"(4) Q3 looks odd...should there be a connection of the drain to +9v?"

No, it´s only go to this .1uf connection, but this one 1M resistor at Q4 Drain was wrong, fixed it ;)




ok here is the actually schem:

Version 3

[Frank_NH]

Excellent progress.  Go ahead and post the photos over at FSB - they will help get any remaining issues sorted out.  And the more photos the better...

[PedalBlotter]

OK, some Pictures again:



Ah sry, its a 470pf/100
Under that 180pf Micas, there stands 220pf.

[PedalBlotter]

The resistor below the Styroflex is for the LED (+)

[PedalBlotter]

OK, looks like my amateur schematic work is verified by the Master himself

by RambleFX » Today, 07:05

Looks good  

It's basically the input triode stages of a 1987x Marshall (in JFET form) into a mini-booster, into another JFET stage.
That's one of the very first Marvel Drives. The ones built now have relay bypass switching, a presence control, and several tweaks. They're much cleaner builds too.

[IvIark]

What's the correct version then?  The V3 link above doesn't work any more

[PedalBlotter]

Actually Version


Here it is.

Again:




Note: Original can be run from 9 - 18 VDC too.
Operating your Marvel Drive at 18 volts will produce a lot more volume and slightly less distortion.

[Frank_NH]

Looks like we have a working layout.  I almost have mine done - should be able to start testing it tonight.

One comment about the layout - some of my caps (particularly the 680 nf) didn't want to sit nicely next to other components.   The 330 uF is hanging off the bottom of the board - but I'll probably change that to a smaller 100 uF.  I also had to do some creative leg bending to get some other caps to fit next to the trimmers.

My request here is if you could add a few rows to the bottom of the layout so that larger components (mainly caps) aren't so cramped.  You could probably reduce the column width to around 20 - 21 at the same time.  I may take a crack at it if I can get some additional components to make a second board.

Thanks for all you do IvIark!

[IvIark]

I've got some 330u 16V caps which are 6mm wide and 12mm tall, and 680nF multilayer ceramics are really small, in fact smaller than the Panasonic type shown in the layout.  Sometimes components are in a very packed out space and certain types or brands of caps will be preferable.  I've got a set of multilayer ceramics and micro size electrolytics for this very reason, and because appropriately sized components are available I'm not too keen on the idea of making a layout bigger than necessary.  But anyone can of course add a couple of rows to allow them extra space if required.