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After much planning, drawing, measuring, parts ordering, more drawing, more measuring, and a touch of creative affirmation from Wilkie1 (for the order\parallel option switching), the Destroyer of Angels is now complete.
I was thinking of something doomy sounding but with some finesse and control. The ‘Life Pedal’ came to mind but I didn’t want an octave circuit involved, so I decided upon a GuitarPCB “Muff-N”, “Rat Deluxe” and “MOSFET Boost” – in that order. But I also wanted to order swap the BMP and Rat – OR – have them in ‘parallel’. (That’s where all the drawing and switching help from Wilkie1 came in.)
I also took advantage of the all the clipping options and Reutz mod for the Rat. For the BMP, I just went with a tasty selection of clipping diode options and the ‘Bender’ mode switch. The MOSFET Boost is simply the stock build at the end of the 3-circuit combo.
Now . . . . . on to the circuit porn . . . .
Because so much depended on the order\parallel switching options, I started with a 4P3T toggle switch. It got fuzzy at at first, but with several drawings and lots of testing, I was able to sort it out. I started with Barry’s ‘order switching’ matrix drawings and modified it to accommodate both order switching AND still provide for a ‘parallel’ option; and came up with this . . . .
HOWEVER . . . . . There is a flaw in the ‘parallel option. In ‘Parallel’ BOTH the BMP and Rat MUST be on (engaged and neither in bypass mode) – else wise the bypass sets ups feedback loop and it “squeals”. Knowing that is important in this wiring configuration.
So here’s the 4P3T toggle fundamental wiring . . . .
With the primary option switch concept sorted, I moved on to testing the guts layout with a preliminary enclosure artwork concept . . . .
With 3 different circuits on the pedal, I opted for a dedicated custom P-MOS based protection circuit – using the following schematic on stripboard . . .
Once all the planning, measuring and preliminary artwork was done, I went to work populating the PCBs. The BMP is using a single LM313 Reference diode (a dual, internal back-to-back diode pair), a green & blue LED pair and a pair hi-Fvd Ge diodes for the various clipping options.The Rat is using a genuine NOS uA308, a pair NOS Telefunken AO7 diodes and a pair UV 3mm LEDs. All the caps (except the power supply filter) are MLCC.
The MOSFET Boost is plain and simple stock, as it does a great job as it is.
And that’s when the wiring started. (I really like the “Vari-Brite” 3PDT wiring boards to allow adjusting the brightness of the LEDs. But I chose NOT drill holes in the bottom of enclosure to accommodate easy access to them.)
And a close-up of the primary option switch harnessing. (Using shielded cable for some of the longer runs to minimize noise in this hi-gain monstrosity.)
And after several plain-paper B&W test prints of the waterslide artwork, I called it good, committed to waterslide stock, went about putting an appropriate candy-wrapper on the enclosure, a few coats of rattle-can clear, then a dozen very light coats of buffed MinWax to complete the protective surface, and finally stuffed it and applied the knobs.
Thanks for looking ! Happy building!
Ah! You are “The Master Builder! This is a marvelous piece of work; a great documentation and well illustrated.
All of our builders should review this to learn some wonderful techniques and tips.
Congratulations, Cybercow! You rule!
Wilkie1 – thank you for the kind words. I but follow the leads and hints found in the various documentation provided Barry and yourself with regards to some of the super-builds you two have showcased here. The inspiration is without rival. And in the words of Thomas Edison: “Ideas are in the air.”
I have also edited the OP to point out the caveat I originally overlooked in the order\parallel switching bit. I believe a more sophisticated switching circuit is required to address the issue.
Really beautiful! Hopefully my builds will look this good someday!
I love this so much. A while back I built a triple pedal that included a Rat and a Muff with individual outs as well as a summed out. I ended up with a similar squeal issue and used a GGG Mini-Mixer tucked away inside the enclosure which resolved the issue. It also gave me additional volume control over how the two pedals summed via internal trimpots. Just an idea for anyone else having that issue!
here’s a link to the Mini Mixer: http://www.generalguitargadgets.com/effects-projects/boosters/mini-mixer/
GAIN MAPPING. I believe the squeal is usually oscillation caused by too much signal level at that particular point in the signal path. When I have combined multiple pedals I found that the output level of each pedal must not overload the input of the next pedal in the series chain. Switching from one to another in the chain will often identify a mismatch in signal levels. It can be challenging to match levels each step of the way through the chain.
Plus 1 on Gain Mapping.
In the case of the combo pedal above playing the circuits in tandem and in Parallel will be much easier to play “noise free” since one circuit is not literally blowing in the doors of one or the other. You are just getting a nice representation of each circuit on their own and at the same time. You can still get a very heavy tone. What I also like is setting one circuit of a “tandem pair” for a low grungier tone and the other either higher or perhaps with a mid bump to offset and compliment the other and doing that is much more “apparent” than if you tried it in series.
Everything above is really easy to test out using our Paramix circuit BTW!
Wilkie1, Barry – if you look carefully at the second image in the OP, (the bird’s-eye-view wiring diagram), you should see the problem when the Order\Parallel toggle is set to ‘Parallel’ and either the BMP or Rat is set to bypass. The caveat in the my switch configuration is that when only the BMP – or – the Rat is on in “Parallel” mode, the output is shorted back to the input. That is from where the squealing comes.
The GAIN STRUCTURE is actually fine when either “Order” toggle position is set. There is no squealing when all three circuits are engaged and all the pots set to max. It is just insanely loud. But the “Parallel” setting works ONLY when BOTH the BMP and the Rat are engaged. And even then, there are no squealing issues at any setting.
Dan nailed it with mini-mixer solution. There needs to be an active buffer between those two circuits when the toggle is set to “parallel” to prevent. the feedback loop thus created when one of those two circuits is bypassed. I didn’t discover this issue until all the circuitry wiring was completed and enclosed. I completely missed that minute detail at the planning stage – hoping a passive toggle configuration would suffice. 🙁
Dn – thanks for that. The Mini-Mixer should certainly address the issue. If I build another, I will certainly employ such a circuit.
And on a side note, without a ‘mini-mixer’ to better manage the ‘parallel’ option, as this entire sits, it draws just under 10mA with all three circuits engaged and all controls at max. It’s amazing how much great dirt can come from such a low current draw.
The PedalPCB ‘Duo-Phase’ I recently built draws up to 120mA. And the Dual-Chorus (paired Mini-Me’s) draws only about 15mA tops. The Dirty White Rat (Rat Deluxe) draws a ridiculously less than 5mA when engaged.
Glad to help. It was my best solution for running a muff and rat to a summed output. The pedal had individual outs for the muff and rat separately, then a summed output of both combined. A bassist friend runs a head that has two inputs to two channels that are active simultaneously. He wanted to run the rat into one and the muff into another. But if he didn’t have access to his head, he wanted to blend both together in parallel into a single input. That’s what led me to sorting this all out and the mini-mixer saving the day for me.
Once all the planning, measuring and preliminary artwork was done, I went to work populating the PCBs. The BMP is using a single LM313 Reference diode (a dual, internal back-to-back diode pair), a green & blue LED pair and a pair hi-Fvd Ge diodes for the various clipping options.
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