blnk page mods

Unholy Grail demo #2

Reverb mix just past half.
Gain and treble backed off a bit and then increased later.

You can hear the reverb feeding back a bit in places which is my absolute favourite thing about this pedal.

Anyone interested can send me a message and I can give you a rundown of how to mod this guy. You could insert any effect you want or even add an effects loop instead.

other vid here.

I finally made a crappy demo of my unholy grail. (With an iPad. Sorry)

EHX Holy Grail with a modified colorsound fuzz box built into the reverb path only.

This is just the hall setting which is much more intense than spring through the fuzz.
Treble and gain controls fully up/reverb mix straight up.
Fender bronco into fender super twin. No other pedals used.
This one is noisy.
Mellower/ambient sort of vid to follow

The plan was to completely overhaul this NYC Big Muff reissue (rev c) tonight. Then my soldering iron died. Bummer…
The good news is the stuff I did get done made a massive difference and I don’t think it needs any more tweaking.
Here’s what’s been done.

Input cap (C1) changed from 1uF to 0.22 uF for less mud. This is essential to the success of my tone stack mod…

diodes - 1st stage (D1/D2) 5mm red LEDs/ 2nd stage (D3/D4) 3mm red LEDs.
This gives a good combination of crunch and sludgy fuzz. They’re also much louder than the stock diodes which make the reissues way too quiet in my opinion.

Tone stack-
Low pass and high pass resistors (R5/R8) both changed from 27k to 39k for less mid scoop.
High pass capacitor (C9) changed from 0.0033uF to 0.01 uF for even more mids.
Now here’s the interesting part I haven’t seen before…
The high pass cap is on a toggle switch so when switched off there’s even more mids (especially low mids) and the tone pot only filters treble. This means I can get any amount of treble without loosing any bass.
I’m finding this even more useful than an added mid control because I always find those too interactive with the tone pot.

It looks like I’ve finally made a usable pedal out of this thing.
And I’ve still got one more muff to tear into…


Darrell rants about the Proco Rat and the ruetz mod.

It’s no secret that the rat is my favourite pedal to ever exist. It’s only drawback is the fact that it can cut a bit too much bottom end for use with low tuned instruments such as baritone guitars, heavily detuned guitars, or bass. The most common mod to remedy this is the ruetz mod. It was the first pedal mod I ever did and the thing that got me hooked on messing around inside pedals. I’ve played around with this mod and the whole rat circuit a ton and am obsessive about getting as much usable low end as possible out of every pedal.
The ruetz mod basically consists of messing around with the 47ohm resistor (R6) that is part of one of two rc (resistor/capacitor) filter networks from the opamps feedback loop to ground. Sometimes this resistor is literally just snipped leaving only the 560ohm/4u7 rc pair to set the gain and low end roll off. Other times that 47 ohm resistor is replaced with a pot. Usually around 1k.
My problem with both versions is that bass is never actually increased. Instead the gain of treble frequencies is actually being decreased by varying degrees. This does give the perception of more low end but in my opinion the decrease of gain in the high end actually robs the rat of its true character. The are tons of “boutique” rat derivatives and rat inspired pedals out there that incorporate some version of the ruetz mod and it boggles my mind.
So what’s the solution?
Well if you know anything about rc filters and especially rc filters in opamp based dirt circuits, you know that the capacitor in that rc pair has an equal impact on the frequencies amplified by the opamp which are then clipped by the diodes. Typically the resistor sets the gain and that resistors relation to the capacitor sets the frequency roll off.
If we look into the rc filters in a rat we’ll see that the 47ohm/2u2 rc pair sets one high pass filter roll off at around 1500hz while the 560ohm/4u7 pair sets a second roll off point around 60hz although with much lower gain.
There are tons of popular mods for equally classic pedals (tubescreamer, distortion plus etc) that involve tweaking the value of the cap in the opamps rc filter to get more bass out of the circuit while leaving gain levels alone.
So why does that seem uncommon in a rat circuit? Why do we ignore the capacitors?
Because I don’t think anyone has written it on the internet yet and a large part of the boutique/DIY pedal community can’t do anything until someone else does it first and tells them how it’s done. The idea of understanding concepts applicable across the board is just beyond some.
So back to these rc pairs…
My favourite version of the ruetz mod was always just replacing the 47ohm resistor with something around 400 ohms which gives a roll off about 180hz while sacrificing a fair bit of gain but If you increase the value of the 2u2 cap instead you can get your low end back without sacrificing ANY gain. 22uf will give you a roll off of around 150hz which is low enough to let most bass frequencies through. This definitely adds quite a bit of gain and compression. The new FatRat by Proco uses a 6.8uf cap in parallel with the 2.2uf cap for a total of 9uf. That value is absolutely a perfect usable value without getting too mushy in the low end.
If you want a tweakable version you could wire up a capacitor blend pot (usually used at the input or output of a circuit) to blend between the stock 2u2 and a much larger cap or any 2 values you want. I’ve used this in several of my own builds and it is massively usable.
Leaving the amount of gain in the circuit alone also makes diode changes much more obvious. Put a big cap (or cap blend pot) in there and a 3 way diode toggle (or even a diode blend pot) and you’ve got a super flexible rat that still has all the amazing qualities of the best rats.

Also check out the comparative rat schematic demonstrating why the “vintage” rat circuit isn’t all that special (with the exception of the lm308). It’d take anyone who can solder 20 minutes or less to covert any rat to vintage specs. My rat 2 was already “vintage spec” other than the missing lm308.

Rats rule.
Use your head.
End rant.


Today’s lazy project was making something much more useful out of an MS10 which is the same circuit as the SM9 and SML.
It’s a very interesting circuit with 3 stages of clipping and tons of tonal control.
First was getting some more volume and some better gain range. Replaced d3 through d6 with 3mm LEDs. Easy. Now there’s tons of output and the gain control sweeps from mellow overdrive through crunchy high gain. I probably could have just swapped out the hard clippers and got enough output considering the additional output the next step got me…
Second was getting some more flexibility out of the “edge” control. This control is fairly similar to the hi tone control in an HM-2 in that it controls the boost/cut of 2 separate gyrators with a single control although the frequencies selected here are much higher making it essentially a fizz control. The high end gyrator is set to around 3khz while the supposed mid band is set to about 1.5khz.
I consider anything over 1k to be treble (especially when playing low tuned instruments) so I left the mid gyrator alone and dropped the frequency of the hi gyrator to around 600hz to control the actual mid range.
R26 became 680ohms
C21 became 0.22uf
C27 became 0.0047uf
Now the “edge” control contains MASSIVE mid range boost and when cut does a decent douchey metal scoop.
This thing can now match my favourite settings from most of my favourite dirt pedals but with its 3 stages of clipping the break up is a bit more complex.