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Hi! I've recently been getting into modular synths, but since I already have an arsenal of guitar pedals I'm not letting myself get any effect modules, instead relying on ways of using pedals in my Eurorack patches.

To that end, I've been researching how to design things that bridge the two worlds, taking inspiration from the Boredbrain INTRFX & Transmutron, the Hungry Robot Modular pedal line, and various DIY "pedal I/O" circuits.

Those pedal interfaces can use Eurorack control voltage (and audio levels), but are powered by regular 9v negative-tip pedal power supplies. Any ideas how to accomplish that? One idea is a TC1044 charge pump for a bipolar 9V supply, and just assume you don't need the extra headroom that the standard +/- 12v Eurorack power supplies. Any other thoughts?

I already asked in a couple of modular synth forums and it's just been crickets...

Thanks!

I was just skimming the new MBP offerings and studying the VFE Fuzz Duo schematic.

This circuit includes an inductor in series with the input, which reminds me of the transformer in front of the FolkUrban variant of the Bazz Fuss, which in turn is nicked from this AMZ article on Guitar Pickup Simulation.

Still learning EE basics, so a few questions:

• Does the inductor in the Fuzz Duo serve the same purpose as the FolkUrban/AMZ transformer (and is a transformer really just two inductors)?
• That is, does it adjust input impedance to help the fuzz function well after buffered effects without losing tone?
• If so, why is an inductor better at raising input impedance for this use case than a resistor?
• If not, what does the inductor do?
• What about the two inductors to ground off the Q1-Q2 emitters?
• How does one select the value of an inductor/transformer for this purpose?

I've got an experimental "fuzzstortion" on the breadboard right now and wondering if adding an inductor or transformer would help it play well with other effects. I don't have either of these in the parts stash, so wondering if it's worth a Mouser order to play around with...

Thanks!

In the past, I've used Pedal Parts Plus and Mammoth Electronics to order enclosures with nice sparkly/veined/hammered/translucent/etc. finishes.

However, Mammoth is now out of business and PPP has moved to a bulk only business, where you need to order at least 25 the exact same customized enclosure.

Other than the flat-color or black/white powdercoat options in some sizes from Small Bear or Love My Switches, does anyone have suggestions for affordable, nice-looking sources of finishes that are a little more "special"?

[D1: WHY DOES ONLY ONE DIODE DO ANYTHING?]

I've been breadboarding an experimental fuzz, combining some ideas from the fuzz face, muff fuzz, bazz fuss, and even the big muff.

Here is the current status of what I've hacked together (my "question areas" are boxed in red):


Quick overview:
* It's essentially a fuzz face topology (with tweaked values) running into a modified AMZ presence tone control
* The fuzz is controlled by an input pot rather than the normal fuzz control (e.g., R5 as a pot)... I found this to sound better & be more reliable
* A switch toggles between a single LED in the Q2 feedback loop vs. silicon hard clipping
* The amplifier output comes directly from the Q2 collector, unlike a typical fuzz face

It's sounding great, but I still have a few questions about how parts of the circuit work, and hope some of you can help me understand my own frankenstein a bit better!!

D1: WHY DOES ONLY ONE DIODE DO ANYTHING?
At first, I wired up two LEDs in a symmetrical typical clipping fashion, as in the big muff, etc. But I noticed only one LED lit up. With further experimentation I realized only one diode going from collector to base on Q2 appeared to do anything at all. The other direction simply has no perceivable effect. This is how things are wired in the bazz fuss, but I suspect you can actually still use symmetrical clipping in a single-transistor circuit like that (e.g., I've seen it in the muffer or 5th gear overdrive). But I'm wondering if there's something particular going on with the coupling of transistors in the FF topology (rather than having two distinct "stages"? Could it be that the feedback loop via R3 is somehow affecting the voltage swing in such a way that only one diode ever matters? If so, is this not a clipping diode in the conventional sense? It really does sound different... and the hard-clipping diodes to ground work in both directions. What gives?

Regardless, that single LED sounds great. It's a harsh, sputtering bumblebee-type fuzz, whereas toggling to the hard clipping network has a creamier distortion feel (and no diodes at all is a beefier, more open and uncompressed fuzz, and of course more output). The tone controls help balance out some of the tonal differences between those three "clipping" options.

R5: THIS SEEMS TO BE THE ONLY WAY TO GET A GOOD SOUND OUT OF THIS CIRCUIT
There's no equivalent to this resistor in any other schematic I've seen... but if you jumper it and go straight from the Q2 emitter to ground via R8 and C2, the pedal sounds... starved. Like the battery is nearly dead or something. The fact that R5 is even there is a happy accident, a breadboarding vestige from experiments getting a fuzz control to sound good in this part of the circuit. If any of you have any thoughts, please let me know!

D2-D5: SUBLE MULTIPLE CLIPPING DIODE QUESTION
I drew things here on the schematic as I accidentally breadboarded it up... with the anodes of D2/D5 touching the cathodes of D3/D4. In this way, it seems like some current can skip D3/D5 without going all the way to ground, but then I couldn't hear any difference when I "fixed" it (D4->D5 and D3->D2 directly, with no point touching in between). The only other place I've seen this is in some (but not all) Timmy schematics floating around. Does it matter to have this connection point between diode pairs in opposite directions? Why or why not?

C10: HOW DO YOU REALLY CUT HISS?
Adding this cap to ground seems to help cut a little bit of high-end hiss/noise out of the circuit (although probably not even enough to bother with the parts count)... However, it doesn't appear to me to be a proper low-pass filter. Any thoughts on why this works or what I should be doing instead are welcome.

The rest of the circuit I feel like I understand pretty well. It's a little low on output... if you dial the fuzz & tone knobs back and crank the volume to max, the effect is on par with unity bypass volume. With everything cranked there's quite a bit more headroom. Based on my research, a fuzz face adds 18db of gain and a BMP-style tone stack attenuates 7-15db of that, and with diodes on that cuts into things a bit more.

Any other thoughts you have about this circuit and how to improve it are welcome. So far it's proven to be a fun, versatile little beast!

Thanks!
(And apologies for cross-posting to other boards)

I'm considering building Zombii (Fuzz Factory variant):
http://madbeanpedals.com/EP/schematics/Zombii.gif

On hand, I have a few PNP silicons but I also have a pair of NOS NPN germaniums that have been gathering dust for a couple years. I feel like at one point I knew some tricks for adapting PNP circuits for NPN, but it's been too long. Anybody have any tips? It should be possible, right?

[The 45 has a 10k R in the input buffer opamp loop.]

I'm trying to learn more about how phase/vibe type effects work (in particular), so my current project is to hack together a "minimal parts count" 2-stage phaser for a 1590a. (I built a MBP Smoothie about a year ago but would like something a tad grittier, hence this project.) Anyway, as a starting point, I've been studying the MXR and DOD circuits, and extrapolated this Phase 90 analysis by Electrosmash to the Phase 45, as well, so I can see the "diff" in these two similar circuits.

I'm attaching screenshots of these "diffs" — blue highlights are minor value changes, green are things added from the P90 to make a P45, and red are things removed from the P90 to make a P45. The main differences seem to be (aside from the obvious 4 vs. 2 stages)...

The 45 has a 10k R in the input buffer opamp loop.
What does this do? (And on 2nd thought, perhaps the other 22k R to REF voltage should really be part of the output mixer section?)

The 45 uses a 4.7v Zener as opposed to a 5.1v.
Does this contribute to the "smoothness" by running things at a slightly lower voltage?

The 45 LFO adds a 150k resistor to ground.
Does this further half the LFO voltage to 2.4v or somesuch, and temper the LFO?

Several LFO cap/resistor values are different.
What do these changes do?

The 45 adds an G/S feedback circuit to the JFETs, with a cap and resistor.
I gather from this post by RG Keen that this loop cuts down on distortion added by the JFETs. Is this correct? If so, how does that work?

The 90 has a PNP buffer in the output mixer
What purpose does this serve? Is there something particular "lost" in the 45 by its absence, or is this responsible for some of the "grit" in the 90 circuit compared to the 45?

More generally, is there a reason these extra components exist in the Phase 45 circuit other than to "smooth it out" relative to the 90? In other words, could you get away mixing-and-matching the "simplest" of these sections, which would essentially be a 2-stage Phase 90 without the PNP buffer in the output mixer?

Bonus question: if one were to experiment with a sine LFO (or some other waveform), how would one do that while keeping the parts count low.

Thanks!

A while back I posted a few pics here of the first few pedals I designed myself, in order to learn the ropes of breadboarding, modding, EAGLE layouts, etc.

I just posted a more detailed writeup on my blog in case you're interested: Designing the JANUS Overdrive

This is mostly a data science blog, but I've been posting more about DIY guitar electronics projects lately (such as transistor clustering for phaser matching and rehabbing an old amp).

Thanks and enjoy!

[JANUS overdrive]

After a few kits and builds from others' PCBs, I decided to start learning EAGLE and hacking together my own projects a few months back. This forum has been a great resource for learning my way around, and special thanks to jkokura, m-Kresol, and markeprice and others for answering my EAGLE and OSHPark questions!!

Last weekend I finally finished my first couple of builds on this journey. They're all are simple circuits based on DIY classics plus some extra mods, designed for 1590a boxes.

Images below link to my project docs, which I'm hosting on Github. EAGLE files are included, if you want to fab your own for personal use. I also have some extra boards from my OSH Park order, in case anyone's interested in a buy/trade!

JANUS overdrive
A mashup of the Dan Armstrong Blue Clipper, MXR Dist+, and DOD 250 with switchable clipping diodes.



GAIUS ringer
Dan Armstrong Green Ringer with a "NULL" pot that varies the intensity of the effect.



CYCLOPS fuzz
This is a snarly one-knob beast. Based on the runoffgroove 22/7 (CMOS attempt at the EHX Big Muff), but with the tone stack stripped out for a flat frequency response, and the sustain pot brought inside as a trimmer. Just a volume knob!

After about 15 builds from kits and PCBs, I'm branching out into hacking/modding/designing my own circuits, and learning more about the basic building blocks. AMZ and ElectroSmash have been good resources, and I've also appreciated the circuit analysis in some MBP projects (like the Slow Loris).

Anyway, right now I'm trying to understand simple PT2399 delays. I started by redrawing two low-parts-count delay schematics to have similar layouts: MBP's 2015 Cave Dweller and Tonepad's Rebote v1 (which appears to just be the manufacturer's example circuit, plus the voltage regular and input buffer?). My plan was to compare and learn from the "diff" between these two schematics.

However, I'm kinda lost.

My drawings of the Cave Dweller and Rebote schematics are attached. Can you fine folks help dissect these circuits for a relative n00b like myself?

Specific questions:

• I'm guessing the JFETs are input buffers to retain tone. However, neither of them look like Jack Orman's example JFET buffer here. How do these two buffers work?
• My understanding is that the PT2399 is notorious for distorting repeats at long delay times (I build a Zero Point Micro II and its delays are too crunchy for my taste). So you have to do a lot of filtering. Where are the filters in these circuits? Is the LED on pin 7 in the Cave Dweller meant to help with the distortion?
• Most everything coming off pins 9-16 on the PT2399 looks wildly different between the two circuits to me. So are they using the LPFs and OAs on the chip differently?
• How does the mix pot in the Cave Dweller work? Is there a corresponding (fixed) portion of the Rebote?

I'd appreciate any help understanding these things. Thanks!

Do they exist?

I can't seem to find this hardware combination at any of the usual sources (smallbear, BLMS, PPP, mammoth, mouser).

Alternatively, I do have some knurled 16mm PCB MOUNT (right-angle) pots that are log-tapered. Any advice on using them as a soldered pot in a one-knob 1590a build?

Hi all,

I have a few boards/kits under my belt, so now I am starting to breadboard/mod/prototype circuits to experiment and learn more. But I've found wiring up offboard components (pots, toggles, etc.) to be annoying: banana clips are often too big and clumsy, but I don't want to actually solder hookup wire to these temporary components, especially if I'm trying to find the "right" pot value, etc.

Attached is a screenshot of some "slide-on" wire terminals on solder lugs I saw in a YouTube video... but I haven't had any luck guessing what these would be called to try and buy some. Any help?

Also, any other tool/hardware suggestions that would be useful for prototyping pedals is welcome. Thanks!

So far I've built a MBP Phase 45 clone (Smoothie) and a GGG Phase 90 clone. I like them both, but sometimes I want one sound and sometimes the other, so I'm tempted to make a more versatile hybrid for my pedalboard. In particular, I'm thinking of the following controls:

• speed knob (duh)
• toggle switch between 2 and 4 stages
• toggle switch for feedback (like MBP's NomNom)

If both toggles are off, it's like a Phase 45. If they're both on, it's like a Phase 90. But you could also have a 2-stage phaser with feedback, or a 4-stage that's clean.

Has anyone tried this? Does it seem like the full 4-way versatility would be worth it?

As for designing this circuit, I could either start with the Phase 90 schematic and add the toggles as bypasses, or start with the Phase 45 schematic and build in 2 more stages + toggles. I'm not sure I fully grasp the subtle circuit differences (e.g., the LFO seems different), so I'm not confident about the best place to start. For example, I don't *think* there are power supply issues to consider if switching between 2 and 4 stages (1 and 2 opamps), but not 100% sure. Any advice is appreciated!!

Related question: Is there a reason that the feedback current goes into the second stage for MBP's NomNom , when it seems like it goes to the first stage in the original Phase 90?

A while back I picked up some baby boards and am really excited to start building them. However, as soon as I started trying to mount the resistors I have on hand, I noticed this:



It looks like too tight a squeeze, and in a few spots I'm not sure I can clear adjacent rows without shorting something out. I'm pretty sure I'm not using oversized resistors, and I didn't see anything in the build guide about needing to use special small ones.

Any advice from experienced baby board builders?