Ramble FX - Marvel Drive 1.0

PedalBlotter · Post by **PedalBlotter** » 08 Jul 2014, 12:54

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 · Post by **Frank_NH** » 08 Jul 2014, 13:20

Nice! I just listened to some of the online demos of the Marvel Drive and it's probably one the best Plexi pedals I've ever heard - just awesome. Bring on the vero!

PedalBlotter · Post by **PedalBlotter** » 08 Jul 2014, 13:30

yes, please someone make a vero !

coldcraft · Post by **coldcraft** » 08 Jul 2014, 14:14

the pin connections on the FETs are incorrect. compare to another JFET overdrive to see what i mean. could you post a higher resolution image?

PedalBlotter · Post by **PedalBlotter** » 08 Jul 2014, 14:25

click on "download this schematic" under that image for a high resolution.

what u mean with incorrect pin connection ?

ah shit, did i mistake gate and source ?

mirosol · Post by **mirosol** » 08 Jul 2014, 14:55

Yup. Gates and sources are in reverse.
+m

PedalBlotter · Post by **PedalBlotter** » 08 Jul 2014, 15:01

Ok i changed it:

download this schematic

tictac · Post by **tictac** » 08 Jul 2014, 16:16

That 820 ohm source resistor on the first gain stage isn't grounded; doesn't look right.....

TT

PedalBlotter · Post by **PedalBlotter** » 08 Jul 2014, 17:38

Yes, u are right.

Fixed it, and the one 1M at Q4 Drain was wrong too

Actually schematic:

https://dl.dropboxusercontent.com/u/357 ... otter3.png

PedalBlotter · Post by **PedalBlotter** » 09 Jul 2014, 09:25

Some Pics:

There is a Wima 4700p cap in, on the pcb it says 470pf...
Under that 180pf Micas, the board says 220pf

---

PedalBlotter · Post by **PedalBlotter** » 09 Jul 2014, 10:00

Ah sry again.

The 470pf is right, my false...
Wima is a 470pf/100 cap

PedalBlotter · Post by **PedalBlotter** » 09 Jul 2014, 10:16

Damn, isn't here a edit funktion ?

Anyway, the resistor below the Styroflex is for the LED (+)

RambleFX · Post by **RambleFX** » 10 Jul 2014, 06:05

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

PedalBlotter · Post by **PedalBlotter** » 10 Jul 2014, 08:31

Thank you RambleFX for verify my amateur work

IvIark · Post by **IvIark** » 10 Jul 2014, 10:22

Q4 still doesn't look right to me:

Code: Select all

Q3 drain > Q4 emitter > 100n > 100K > Q5 gate
                 V
                1u > Q4 gate

PedalBlotter · Post by **PedalBlotter** » 10 Jul 2014, 12:22

Hmm, i checked the circuit a hundred times i think.

it must be right like on the schematic ?

:

Actually Version V3

Pics from Q3 and Q4:

----

....

jubal81 · Post by **jubal81** » 10 Jul 2014, 13:26

I redrew for clarity. Looks pretty reasonable. The only thing I see as weird are the parallel 220uF & 100uF caps on the source of the 'normal' j201 input.
Here's a link to the full image

IvIark · Post by **IvIark** » 10 Jul 2014, 13:39

Aaah muamp! I couldn't see the wood for the trees

IvIark · Post by **IvIark** » 10 Jul 2014, 13:45

jubal81 wrote:I redrew for clarity. Looks pretty reasonable. The only thing I see as weird are the parallel 220uF & 100uF caps on the source of the 'normal' j201 input.

The 1987X has 330u from source to ground in that position.

PedalBlotter · Post by **PedalBlotter** » 10 Jul 2014, 14:35

Nice work jubal81.
Looks clearer and cleaner than my experiment

i see, the treble/normal pots are backwards on my drawing

C10 is a polarized 1uF 50 Volt + to Gate Q4

C6 is a polarized 0,68uf 100 Volt

if this is necessary ?

Ramble FX - Marvel Drive 1.0 [traced]