I finished a ROG Umble and...

[Frank_NH]

...I love it!


Like the Britannia, this is an amp emulation circuit that is supposed to sound like a Dumble amp.  I don't have any idea if it sounds like a Dumble, but it sounds great in it's own right.

This circuit was built from a PCB from TH Custom Effects (great vendor for PCB projects!).  I used all J201s from my tested stash, with all four JFETs being about the same as far as operating parameters are concerned: Idss ~ 0.3 mA, Vp ~ -0.7 V.  It fired up right a away and the JFETs biased to 5V with no problem.  I should note that my build used 50K trimmers versus the 100K suggested by ROG.

The board mounted pots make for a very neat and compact installation.  The controls are Master Volume, Volume (Gain), Treble, Mid, Bass.  The sound is very good (smooth without any hint of spitty decay) throughout the gain range and the tone controls are very interactive and effective (especially the bass control).  It could use a pinch more treble at times, but overall it sounds about right.  One thing I noticed is that if you turn the volume up and the gain down, the treble is enhanced a little.  This is my favorite setting:  Volume at 75% and gain at 50%.  You can also get some very nice high gain distortion by maxing the Gain knob.

I liked this circuit so much after my initial tests that I went ahead and boxed it up today.  One thing about the pot layout - the pots are side-by-side on the PCB, so you need skinny 1/2" knobs for the controls.  Not a big deal, but I didn't have anything appropriate so I'll have to order some knobs.  

I'll be boxing the Britannia pretty soon so then I'll have both British AND American amp pedals .  It will be interesting to test them together and with other pedals (e.g a booster) in front.  I'm hoping to use both of these at my next gig.  Rock on!

[dbat69]

Very nice tidy build Frank, and thanks for the heads up on the PCB supplier

[Frank_NH]

Well, it looks tidy because it's in a big, ol' 1590BB.  But I'm not too particular about enclosure size and would rather have a box on the larger size versus smaller (125B is my favorite).  The five pots really dictated the need for a 1590BB (for me).

As for PCBs, I have adopted a policy now that if there is an interesting effect I want to build that is available as a PCB, I'll get the PCB.  The cost is minimal considering the time it takes to prep a vero board.  However, vero does allow me to explore and mod to my hearts content, and to build effects for which there are no PCBs.   As I've stated before, I'm not into etching PCBs, even if a layout is available, as I'd rather build/test/play effects versus going through the labor-intensive etching process.  But that doesn't mean etching your own can't be fun - heck, my Dad used to do it for his electronics projects.  

The PCB suppliers I can highly recommend so far are:

TH Custom Effects
Aion Electronics
1776 Effects

And of course there is Madbean Pedals, who I haven't ordered from, but many have and are excellent.  (I did build the Madbean Rump Roast on vero, and that is one of the best smaller builds I've done - just a great-sounding small amp sim).

For those building the Umble on vero or PCB (or any other JFET-based amp sim for that matter), do make sure you test your JFETs.  I've been finding that I can get very predictable results when I know the IDss and Vp for the JFETs.  And it's always better if you can use a drain trimmer that's < 100K as it makes dialing in the bias much easier.