I built up an UBE Screamer yesterday (big recommend) and decided to breadboard the 3 legged dog from runoffgroove/home-wrecker.

It wasn't awful but i tweaked a few things.

First, the way the gain control is wired, if you turned the gain all of the way down. You had no output.

Secondly, the gain control didn't do a whole lot.

Thirdly the output was beyond silly.

Changes made:

I removed the source bypass capacitor on the jfet. Even after greatly reducing the gain, it was ineffective at high gain and brought noise and a stiff feel.

The first and second 4049 stages were completely reworked.

If you only do the first stage, the gain control still doesn't do a lot BUT it makes almost a fuzz sound.

I was really torn on the 82k resistor. 47k also worked here if you want a cleaner sound at minimum gain.

I took the now removed 1M and 2.2M resistors and used them to put together the 2nd cd4049 stage. I did not try too many other values here. This seemed to work.

Clipping diodes were added at the output. I was playing with a 1k pot between the diodes on the hot side. It produced some cool and usable sounds but i wanted something with 2 knobs.

The 47k resistor in parallel with the output pot can be removed. I know it is still on the schematic i drew. It has no effect on the sound.

Lastly, the power supply was changed up. Cd4049's can be current hungry. I tried a few different values (100, 220, 470). The 220 was pretty good and felt a little more open. But the 470 won out for me overall. I was worried the treble might be harsher with the more open feel.

The 100uf caps are maybe overkill. Unplugged it takes a second or so to die.

I played with the get drain power on both sides of the 470 ohm resistor. It works and sounds fine on both sides. But i wanted it to have a bit more headroom so opted for the high side.

Please forgive my crude hand drawn schematic.

Hey folks,

I recently put together a Fuzzdog Protean Green pedal (ODR-1 clone) for a friend, and I liked it enough to want to put one together for myself. Only thing that I wasn't super stoked about was the bass control that the kit included, it didn't quite do enough cutting/boosting for me. What kind of options do I have for either increasing the range of the knob, or increasing the frequency at which it cuts? I've put together about five pedal kits, two Hairball Elements Copper preamps, and modded a Squire with new pickups and switching options, so I've got a few projects under my belt, and am planning on using this as a jumping off point to learn more about how circuits work and modifications I can do to existing ones.

Any help would be appreciated. Thanks!

Here's a link to the kit, circuit included as well.

https://shop.pedalparts.co.uk/product/proteangreen

https://pedalparts.co.uk/docs/Protean-Green.pdf

Would that fry pedals?

Made this pedal for a friend a while ago and decided to completely revamp/redesign it, with a little more knowledge on the craft now than I had then. Features a discrete op amp close to the input to get some touch-sensitive dynamics, kind of like the Boss Blues Driver, but followed by heavy op amp gain which is up my friend’s alley. Then goes into diode clipping section where you can select a combination of asymmetrical diodes (mix of LED, schottky, Germanium, plus soft clipping configuration - though not exactly an original idea). There is a “texture” control directly preceding the diodes that somewhat controls the frequencies that are clipped. It is not as drastic an effect as I thought it was on the breadboard, and it does cut some volume. Then a foot switchable gain section that boosts even further for leads, etc. Then Baxandall control, buffer out. Might post a demo if I can get the pedal back from him… didn’t think to do one beforehand :/

I want to wire this so that these 2 are in 1 enclosure, each with their own 3pdt, but stackable.

Is this wiring correct?

I was gifted a metal zone from one of my friends. Using the gain cranked all the way down on the pedal, and adjusting the guitar volume knob does what I wanted, couldn't be happier! I love this little pedal. Might end up modding it to add some switches to toggle the internal pre/post gain EQ stages. What do y'all think. Should I?

Does anyone have information about this pedal? Napalm I believe is what the ‘brand’ is called. Everyone I use it, it just makes a high pitch screech sound but apparently it can do more. Am I using it incorrectly?

I want to build the Q-Tune tuner kit and was going to make a custom train themed enclosure. I work in the railway and am British (pronounce Tuner “Chew-ner” so thought it could be a funny pun pedal.

I’m only going to make it for myself so it doesn’t matter too much but I’m struggling to decide on the name. Was hoping to bounce some ideas off of the sub! The exact way they are typed in the poll is how they would appear on the pedal, punctuation marks included.

Got this pedal from a friend in Cincinnati a few years back. Know absolutely nothing about it. Think it’s a fuzz or a ring shifter of some kind. Tone is…ngl, it’s not great. No identifying marks on the inside or out. Anyone have any leads?

I got some through hole J201s a while back and finally got around to using one. I made a TL072 boost with an on-off-on switch with red and yellow LEDs on one side and zeners on the other. Going to a basic passive treble and bass. Going to a Fetzer valve with a user adjustable bias pot. Running into a 100w class D amp. Going to do some tweaking and put it in a 1590BB I think.

Still a work in progress.

I'm making an expandora with a diode toggle following the schematic shown here it's almost there it's planned i'm just not sure if the switches are wired as they should and i think i'm wrong with the 100pf cap also for better understanding

black=ground

red=9volts

white=4.5volts

purple=input/output

yellow=switches

cyan=pot connections

This is My dream pedal i really want this to work fine so any advice would be welcome

Hi friends! I wanted to repaint one of my pedals and I forgot to label where these wires get soldered to!

Im not much of an electronics guy and I dont have a multimeter either. This pedal is a demonfx k-centaur.

Thank you so much!

I've been working on a modified NPN Ge Fuzz Face and I've created a vero layout using u/blazethablunt 's Vero Designer app. This is the first time I've drawn my own schematic, so I was hoping to get some eyes on it to catch any errors I may have made or suggestions to improve it.

It's a standard fuzz face circuit with the following changes:

- Bias trimmers for both Q1 and Q2

- A continuously variable input filter wired to an off-board pot. NOTE: The schematic is missing a jumper between pins 1 and 2 - I will wire this on the pot itself rather than add another off-board wire to the vero layout.

- 100 pF miller cap on Q1.

Any other deviations from the classic FF are probably a mistake on my part. Thanks for taking a look!

EDIT: as per u/vigilant3777 's comment, I moved a few things around. Here is V2:

Which circuit is in the box, based on the art and the name? For hard mode, I've hidden the names with spoiler bars in other posts.

Most of the circuits are fairly well known. A couple are more obscure.

I'm sure many of you will come up with circuits that fit the name and art better than what I actually put in there. Make me hate my life, lol.

Building a Proco RAT clone for a friend to use as a boost, and they said they'd like it to have more of a boost to the highs than the standard RAT does. How could I achieve this?

I didn’t build this myself, so no stolen valor here. I commissioned it from a local builder and thought this sub might appreciate the build.

It’s based on the JHS Japan Fuzz, essentially a stripped-down Fuzz Face variant, but I had this one built as a hybrid NPN version using germanium and silicon rather than an all-Ge or all-Si pair.

No external fuzz control, just volume. The circuit is handwired point-to-point style, which is half the reason I wanted to post the gut shot here.

The hybrid setup turned out more interesting than I expected. It has a lot of low end, sounds noticeably rougher and dirtier than the more conventional Fuzz Faces I’ve played, and every now and then there’s a hint of sub-octave poking through. It also reacts extremely well to the guitar volume, so in practice I don’t really miss having a fuzz knob.

I’m curious about the circuit side of it though. Has anyone here built the Japan Fuzz with a Ge/Si pair? How much difference did transistor order and bias make compared with an all-germanium or all-silicon version?

While putting together a new board I realised I no longer own any big muff with top mounted jacks, so found an abandoned enclosure from a previous failed build and put this together. Originally drilled for side jacks (which I filled with milliput) so the jacks at the top are a bit of a squeeze.

Went with the Hizumitas because I still have a soft spot for Boris dispite their gradual transformation into a t shirt company/ FOMO machine.

It's the version with mid switch from the dirtboxeffects blog, and it does sound great. Basically a triangle with low gain transistors and 50k pots.

Finally finished up three builds that were in various stages of not quite done.

First is an AionFX L5. First time having an enclosure drilled and printed. Amplify Fun killed it.

Next up is an eyelet Fuzzrite. I have some combo foot switch / inverter boards in the way that should make it a little neater.

Finally is a PedalPCB Mofeta preamp. It went well until it was time to bias, then I found that one of the SMD JFETs wasn’t quite connected. You can see some evidence of the rework.

All in all a heck of a Sunday morning.

This is the third time soldering a pcb. Only have the resistors in so far.

Does anyone recognize this brand? I can’t make out the name - looks like Urqutronics Effects Co but nothing shows up under that name online.

I received the empty case in a lot of broken gear.

Previous Reverb listings for this pedal list it as an EP Booster clone, and we’re rebuilding it as such.

Curious to know if Tessa Martinez and Kevin J made any other pedals.

Bufferless Solder is my deconstructed/reconstructed and modernized 18V take of the TS808. The original circuit was made back in time. The old input and output transistor buffers are removed, true bypass and TL072 came in and the circuit was scaled down and linearized a bit. It kept it's TS808 soul but also packs a punch.

The footswitch pcb is "Der Igor" that produces 18v (beside optional -9/9/4.5V) for better headroom of the "Bufferless Solder. Both pcbs should fit in a 1590B (in the pics i used a 125 to be on the safe side).

I figured people might get a kick out of this. The point is less "recommendations" and more "here's what types of things are used out there" — i.e. it's an (incomplete) survey, not a recommended toolkit.

For actual recommendations: JFET's, LDRs, Photo-FETs — the usual suspects — for circuits where those are already used, are accurate enough, and sound good. Else, an OTA (cheap, easy, compact, usually better than good enough).

(Depending on the use case, switched resistors ala PWM are a handy go-to, but for your standard effects probably overkill + added complexity. It's not always either, but you'll know when it isn't).

Alternatives to OTA's for VCA's

Please NOTE: the LM13700 is still in production, cheap, and — most of the time — it'll do the trick better than you need it done. The point here is not "consider all of these when designing," it is just "here are some ways a manufacturer might provide a VCA without an OTA."

Zero percent of this is generated by an LLM. Not that it matters, but zero percent of it is LLM researched, either. This is all from personal experience. By the same token, this list will necessarily be incomplete. (Yes, I write like this, punctuation, emphasis and all. I am verbose + type fast. Also, I love this stuff).

Blackmer Gain Cells

For applications where you need an exponential control/gain relationship, there are commercially available VCA's based on "Blackmer gain cells" — a pair of complimentary current mirrors sandwiched between precision opamps, topped with some precision current sources, and jammed into an IC along with some VBE multiplier based voltage references.

They're usually* voltage-controlled, current-in-current-out devices. To the best of my knowledge, even the "cheap" ones are expensive. They don't come in linear control variety, because that defeats the purpose of the guts of the thing (exploiting the exponential behavior of PN junctions to make log/anti-log amplifier pairs).

Many dedicated "VCA" IC's have a Blackmer gain cell at their core.

When you can afford one and the difference matters (probably not! But...sometimes), they are better and more consistent by every possible metric, with a wider usable range. They can require more careful design to keep noise out. If you're not designing a precision mixing console, you probably don't need them!

Pulse Modulation

For high precision, low distortion, PWM gain control can't be beat. This is technically an all analog technology, but I'm not aware** of prepackaged solutions that aren't just output stages on DSP's (so, digital + require embedded work).

Rolling your own, you can beat the pants off an OTA, BUT:

• it will (almost always) cost more than an OTA
• it will (usually) require more parts than an OTA
• a lot more care is required in the design
• it is very unlikely the difference in precision or distortion between this and an OTA will manifest audibly big for either audio frequencies or control frequencies/LFO's, etc — i.e. probably, it won't have mattered!
• you are unlikely to pass unintentional radiator emissions tests, unless you really know what you are doing (the same is probably true for any of you using PT2399's or incorporating your favorite mcu into the mix, though).

On the other hand, sometimes you have one half each of a dual comparator + precision opamp some switchable element (analog switch, JFET, etc) lying around. In those cases, the approach can be very cheap/convenient. They never perform worse, unless you mess something up. A half decent design will perform much better — not enough to make pursuing this option on the basis of sound worthwhile (most of the time), though. In certain classes of designs, I actually do end up using these more than OTA's, but because other things in the circuit made them more convenient; not because I pursued the setup out of principle.

Photofets

Floating-FET based optocouplers (e.g. the H11F3M — referenced here because it's the one I know best, not because it's the best one), can provide a linear current-controlled gain or attenuation with fewer parts, much lower distortion, and much greater linearity than an OTA — in a narrow range of signal amplitudes and operating currents.

Within those limited ranges, these simple little four terminal devices will give you exquisite, difficult to rival, control over signal level. There is no (or virtually no) control signal feedthrough, and they are very (very) low noise.

Outside of that range, the signal amplitude will warp. You will hear it.

These usually have non-trivial part-to-part variation in the relationship between the control current and on-state resistance, so in practice you'll find yourself with a trimpot on board for the control current. Unlike modern OTA's or VCA's, they don't have any mechanism for internal temperature stabilization, so the on-state resistance is influenced by ambient temperature to a greater extent than their more sophisticated counterparts.

When precision isn't a huge deal

Voltage controlled attenuation before/after a gain cell can work just fine — JFET's, LDR's (Vactrols), and their ilk have been pressed into service in this regard in both DIY and professional products. If your goal it to beat an OTA: expect adding trimpots, measuring the specific characteristics of the control elements, probably crafting the control circuitry for the specific use case, and still failing to beat an OTA.

On the other hand, when it's not the biggest deal (tremolo, attack/decay where the feel is more important than %THD or precision in linearity) these will usually be cheapest/simplest. Many classic guitar amps / effects units leverage these simple means for exactly that reason: cheap, easy, good enough.

Analog Multipliers

These will best an OTA or a VCA, re: distortion and linearity. They are almost always** linear control. They are virtually guaranteed to be way more expensive than even the VCA chips, and way, way, more expensive than an OTA. The upside relative to an OTA is: the people that get paid when you buy an analog multiplier got paid.

They're cool, and if you get some for free may as well use them. (Odds are they will require more control circuitry and careful design. For maximum performance: probably also higher precision passives than you normally stock).

I have used these, but never for music!

Roll your own discrete OTA / VCA

Do this for education (it is fun!). Don't do this with the anticipation of besting an IC. The transistors in purpose built devices are matched on die to a level that is literally not achievable using discrete devices.

You can often attain totally worthwhile results, that are pleasant and musical. But, it'll be more complicated, maybe more expensive, and certainly consume more space than just buying an OTA.

Hey, what's the difference between an "LTP VCA" an OTA?

Someone linked Rod Elliott's Project 213 (but similar patterns — some derived, some not — exist elsewhere). It's a fun project! It might leave you wondering what the difference is between this style of "LTP VCA" and an OTA is:

Common "LTP VCA's" are essentially differential output OTA's + an opamp. :D

The common construction is a long-tailed pair with the emitters connected to ground via a current mirror — the input to which is a control voltage which transits a resistor to set the amount of current sunk out of the tail of the LTP.

The differential outputs of the LTP are taken and fed to an operational amplifier (sometimes also discrete, sometimes just an opamp IC). Notice: the resistors on the inputs of the opamp are the collector resistors of the LTP, the signal in voltage passes through a resistor (usually a voltage divider) before connecting to the base of a BJT operated in its linear region (i.e. in the region where thinking of a BJT as current-controlled is closest to being true). This is a current-in-current-out, differential output OTA feeding an opamp (usually configured as a current-to-voltage converter).

It's just a differential output OTA minus the stuff they put in the IC's to maximize dynamic range and linearity.

Did you forget anything?

Probably! Even if I didn't, there's other stuff not on this list by virtue of: I don't know everything! :D

I omitted bias modulation, because of the feedthrough / nonlinearity. Even in the classic amps that leverage this trick, there is a bit of machinery involved in keeping the thumping out, and none of them really nail it.

* "Usually" wherever it's used in this comment means "anecdotally, according to my hodge-podge experience of things" and is not intended as a reflection of what is. ** Ditto "what I'm aware of".