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Rump Roast Treble

Started by jcuempire, February 23, 2011, 09:25:20 PM

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I love my new Rump Roast but it's got gobs of high end.  Is there a place I should start messing about with different values?  I am still learning so it would be a lot stabbing in the dark.  But it's a great boost / overdrive (I built the hybrid) excepting the treble bit.  Thanks


Yes, increase C5. The doc indicates 680pF. Try 4n7 or 6n8.



I made the change and it did help, but it's still pretty bright.  I assume I may have another problem.  Question, though.  Is the Tone control supposed to work like a RAT filter (bright fully counter clockwise - 8 o'clock)?  If not I have it wired backwards or something.  Also, it seems to only have any effect at the last 10% of the pot travel.  The other 90% is just bright.

On the other hand, putting it ahead of my fuzz face is great.  It's a preamp section that controls the distortion.  And the FF plays nicely with it.  There are other pedals that really don't.






I'm a noob myself but I wonder if you have linear taper pot instead of a logarithmic taper pot if you only get response from the last 10% of the travel?



Keith, the tone knob is supposed to work as a cut in the RR, just as it does in the Carmen Ghia amp that it's modeled after.

If it is still too bright at any setting for you, then you just need to keep upping the values of C5, C6 and C7. There's really no correct value here....this kind of boost is going to handle itself differently in different gear set-ups. This is why I included the switch---to give you two tonal ranges to choose from.

I would socket those caps and try some combinations. Here are some suggestions you might try:

4n7        68n          22n
6n8        68n          33n
6n8        82n          15n

At some point, you will find the right balance between bright and dark. You can also use a linear pot instead of audio to change the sweep.


Okay.  That's cool.  At least I wired it up correctly.  I will try some combinations like you suggest.  And it's a good idea to socket them, as I would eventually destroy the board, no doubt.  The switch works great and the second setting has some serious stones.  I like it alot

As always, I appreciate your help.  I'm all set to build the T-Bagger!



I found part of the culprit.  Seems the output jack was making contact with the case of one of the pots when plugged in.  After swiveling it around and resoldering some of the components, suddenly it sounds alot better.  There used to be a volume change between the two tone modes that's gone now and it is not as bright as it was.  But I still don't get much change with the tone pot.  But, it's certainly getting better overall.  Just keep plugging away at it.  Thanks for everyones help


The best way i've found to make sure a pot is good and fully working is to test it with an ohmmeter or use the continuity setting. touch your probes from outside lug (3) -> middle lug (2) and turn the pot. you should see it go from zero to full resistance or vice versa. Then do the same from outside lug 1 -> middle lug 2 and see if its same. To the best of my knowledge this will tell you if the pot is working correctly!
Owner and operator of Magic Pedals


Thanks.  I'll try that tonight


bigmufffuzzwizz - I tested the pot and it's working fine.  I'll start looking at all the values of the components and see if I can spot a mistake somewhere.  Thanks