Messages

Yes, but WHY? Why would you replace the gain control with one that has only a tiny fraction of the same range? If you want to know how restrictive that will be on this design, grab another distortion pedal you've built and put the gain pot all the way up at 5:00. Now put the gain pot at 3:00. That's about how much range you'll have if you replace it with the source bias control and hardwire the gain pot spot to max like you've drawn. Is it JUST because you want to use the gain control you saw in the Fatpants? You can ADD that without removing the current (actually useful) gain control from the pedal. There's only three knobs on the stock design.

Yeah... I dunno. I think I'll follow that and add it without removing the gain control. I want a pedal that will distort, sure, but I want to be able to change the character of that distortion. If I'm not mistaken there are some settings that sound "raunchy" if you bias the transistor to a much lower voltage, like 8v instead of 11v.

Think of the "gain" control as a "character" or "response" control more than a gain control. My understanding is/was that the bias of the transistor affects not just the gain but the "deformation of the sinusoidal waveform upon excitation" (the Aquataur article about his umble modifications talk about how he does this).

I wanted to take out the existing gain control so I could limit the design to four knobs - "range," "timbre," "treble," and "volume." I almost never fiddle with the gain settings on my OD pedals once I have them set to where I like them - I much prefer to use my volume knob. I had planned to use the fixed resistors to set the maximum gain level to where I wanted it and then free up that real estate so I can have more knobs that affect the character and response of the pedal.

You don't have to use those exact values but you do have to use their mathematical equivalents if you want the same range. You can calculate it here: http://sim.okawa-denshi.jp/en/CRlowkeisan.htm

Thank you for the link - I'll be sure to plug in the requisite numbers and figure everything out.

I hope this doesn't sound rude, but I honestly have no idea why you'd want to use the topology of a pedal that's designed to create distortion if you don't want a distortion pedal. If this is what you wanted, you only need the first two stages. This is an awful lot of work when you only need 1/2 of the layout.

It's not rude at all - I am asking quite a broad array of questions concerning things I don't fully understand... Of course I'm going to sound idiotic. That's the price I pay for being too lazy to teach myself more of this stuff. On the contrary you've been very patient despite my persistent stubborn disposition lol.

The 1M bias resistor is negative feedback, but only incidentally. It's a biasing resistor.

In Fender amps, the presence control impedes a cap to ground hanging off the cathode of a tube that's also connected to the negative feedback. The presence pot forms the second leg of a voltage divider with the negative feedback resistor. When you lower the impedance to ground, the tube's gain for high frequencies increases and high end content is removed from the negative feedback. (When you remove frequencies from negative feedback, you get more of them in the final sound.)

There are lots of places with negative feedback in the circuit already. The source bypass cap on Q1 is a form of negative feedback. The compressor circuit is a form of negative feedback. The Q5/Q6/10uF/33K series is also negative feedback, and it's also the primary source of clipping in the pedal. The negative feedback in that arrangements ONLY appears when the signal is large enough to clip Q5 and Q6, which are diodes (the threshold is about 2-3V). Then it's limited by the 33K, which appears in parallel with the 1M for large signals.

But here again, I'm not sure what the point of adding a "presence" control like you describe would in a pedal that already has a treble control near its output. The treble control here is basically in the same place an amp would have its treble control.

The "presence" control would function differently in kind than the existing treble control - my understanding is that by introducing the frequency-specific negative feedback you change the rate and levels at which different frequencies clip. Because the audible effect of clipping occurs in the treble frequencies, I wanted the treble frequencies themselves to be less clipped - rather than simply rolled off late in the circuit. So yes, there would be more treble frequencies as a result, but the intended effect would be to decrease the actual clipping of those frequencies.

Additionally, in conjunction with the compression circuit, I wanted the effect to be clearer-but-still-compressed high frequencies and more distorted midrange/low frequencies.

I think what I'm going to do is this:

- Leave all the PCB mount controls untouched
- Change q1 to a MPF102
- Add those micro-shaft potentiometers for any additional controls should I decide to go that route
- Practice more instead of thinking of quirky ways to make circuits less useful lol

Hrm. There's a lot of things you've asked here that are looking to implement duplicate functions.

As I see now you're quite right... Unfortunately I get obsessed over OCD things that don't really have much of an effect on sound as it were.

The purpose of putting a gain control on the source is that it doesn't require components to decouple the gain control from the biased pins of the transistors, and because your gain control won't load the devices unduly. That's unnecessary in this design -- the gain control is already decoupled from Q1, and the loading is designed into the pedal. It also forms the gate biasing resistor of Q2. If you were to replace it, you'd have to add the biasing resistor, and then to make the source variable, you'd have to replace the source resistor with a pot of appropriate value, probably replace the trimpot with a larger value, and then add the 22uF onto the wiper.

I had planned on doing exactly this - I have attached a drawing because I feel like it would be easier to understand than my haphazard rants lol.

At that point, once you bias the FET, you'll have a variable gain that only attenuates about -6dB, because that's the gain boost you get when bypassing the source resistor on a FET that's been properly biased. The current gain control can go as low as -20dB. You'd be stuck on the right hand side of the dial, and I can tell you that I pretty much never set the gain above noon as it is.

I actually had planned on using it in conjunction with a few other modifications to reduce the gain - I would replace the gain control with a couple of resistors to approximate the gain control if it were set to noon (for example - I'll have to experiment with their values should I go this route) at the gate of q2.

Before I get to the input loading -- you can use the omega's large drain and source capacitors. The MOSFET in the omega is simply an output buffer with some specialized function (that isn't so different from having a FETzer valve biased a little high); the MOSFET doesn't increase the gain. The biasing affects how the FET clips; the 4u7 maxes out the gain.

After reading the section of the fetzer valve article about harmonic content (which is why I ordered a 340R resistor to use a mpf102 in q1) I'd prefer to use the lower-resistance values, but I wasn't clear as to whether the efficacy of the range control depended on the resistance of the circuit. My question was phrased poorly - what I meant was "do I need to use those values to get the most out of the range control?"

That's what it is already! It's four stages that boost the signal by ~6dB each (the first is +12 for frequencies near 1KHz).

This is true... I wanted something like a treble booster running into an echoplex. The treble booster to reduce bass, the echoplex to add texture. Essentially I wanted a pedal that acts like a sort of preamp rather than an OD pedal - cutting some bass, adding some texture to the mids, and pushing my tube amp.

If you're looking for Fuzz Face type of clean up, you simply won't get that in this circuit. The Fuzz Face has a slew of things that make it behave like this, but the big ones are (a) negative feedback circuitry; (b) the use of a BJT, which can be biased all the way down to 0.5V, which means that it's far, far more sensitive to the input signal size. The Fuzz Face also treats the pickups like a current source instead of a voltage source, which is not something you can duplicate here.

This brings up another question I had - re: the MOSFET section of the circuit - isn't there some negative feedback already in the design? I had seen on a fender amp schematic a presence control (which was a variable NFB loop with a capacitor to increase the amplified volume of treble frequencies relative to bass at the power amp stage) and was curious if I could do something similar in conjunction with the existing tone control. Essentially a dual ganged pot that rolled off highs before the power amp and increased the highs in the NFB loop at the same time. I know my language isn't precise here - my understanding is that NFB reduces overall distortion and makes the onset thereof more binary. And, it's been a while since I've seen the schematic, but IIRC the fender control in another part of the circuit would have rolled off bass rather than high frequencies? Something about the nature of NFB meant it had to work in reverse to get the desired effect. I know that's a lot of mumbo jumbo and I apologize for it.

The size of the drain and source resistors isn't the big reason the Omega boosts that much. In part it's that it's a J201 whose gain has been maxed out. A J201 is perfectly capable of hitting the power rails. Even without a source bypass capacitor, the J201 will boost by ~13dB. Add a source bypass cap at idea biasing and that's almost 20dB. Increase the size of the source resistor so that the cap has a bigger effect and you get the Omega's gain stage.

When reading the ROG article, I somehow got it into my head that the Omega used a 2n5457, and the claim on the site - 30-35db - made me curious as that was well in excess of any gain figures I've heard about the 2n5457 before (on 9v, I'm sure you could get there by upping the voltage.)

The Omega's input loading is there because it's how they chose to implement a Range control. It cuts bass as you turn it down because it forms a low-pass filter with the 3n3 cap. You could add all that stuff ahead of the 33K, but I'm not sure it's going to do much. In any case, if you choose to have the Omega's bass control, you probably want to make the source bypass cap on Q1 a larger value.

These are the droids I was looking for - I wanted to know if it would be a worthwhile endeavor to add the range control to affect the EQ of the pedal. If it's not going to do much then I figure I can just add the fat boostered/paul cochrane passive bass rolloff to an input buffer or something and get a similar effect.

First you need to be aware that getting 24V means using a 12V supply. Don't try to give the LT1054 more than 15V. (You can give it 15V REGULATED.) Then go check the Fetzer valve calculator to see what sort of gain levels you're looking at with the 2N5457 on 18V, and compare that with the MPF102 on 24V. Then put in the values for the 2N5457, because you have two more of those in the circuit.

This is what I do with my fatpants - I use an lt1054 with a 12v supply (and a 12.1v zener diode) because I like the sound more at 24v internally than at 18v internally. I've heard but cannot confirm that the mpf102 is near it's limit at 24v and maybe this makes it sound better to my ears? At any rate I know I want to do the same with this circuit - not because there's a valid scientific reason to do so but because it's something different and I'm weird like that.

I think you asked before about the Fat control. The circuit must be designed around using that kind of gain control, because you need to be able to bias the FET so that the variable source resistance doesn't bias it into cutoff on the low end or oversaturation on the high end. I know you can get this range with a 2N5457, barely, and a J201. The Fatpants simply doesn't work with lower gain FETs, though.

Note that the Fat control from the Fatpants changes the biasing. The biasing is important in this circuit because it affects the way the signal is clipped. Altering one of the FETs bias as a gain control may produce unsatisfactory results. This isn't an issue in the Fatpants because the clipping there is incidental, not intentional.

This is exactly what I wanted with a fat control in this application lol - having read aquatarius (I think that's the guy? He's the one you linked to in discussing the compressor circuit you use with the flabulanche) he mentions that he got FETs to clip more like a tube amp using lower source resistors than those proposed by ROG. However he doesn't provide any formulas for figuring out those values and I don't own an oscilloscope so I can't actually test the JFETs myself. The purpose of the "fat" control in my proposed circuit is not so much to change the gain level (I plan on using my guitar's volume knob for this) but to alter the timbre of the pedal and the clipped frequencies. Ideally I'd use it in conjunction with the range control (and the dual ganged treble/presence control I mentioned earlier) as a sort of tone control affecting the character of the pedal.

If you want to audibly affect the bass, do it late in the circuit. The circuit is already full bass after Q1. Any cut to bass before the MOSFET stage will primarily affect distortion. The reason the bass cuts are there on and right after Q1 is because the distortion will sound very tubby without them. This is simply good gain staging. Also, your Range control is already going to be a bass control if you do it like what's in the Omega.

Okay, so having different source bypass capacitors on q1 is unnecessary. That's excellent news. I'm not looking for a tubby distortion at all - quite the opposite - and not having to worry about a 'body' switch is great.

So, here's the circuit with my proposed modifications (excluding the charge pump):

edit: it's loading upside down, trying to fix now
double edit: will have to fix later today



If you can't read the notes I'd be more than glad to clarify anything and everything.

As always, thank you for your help - I can't tell you how much I appreciate it.

Awesome - thank you for the response and sorry for derailing the thread.

I planned on using an mpf102 in q1 to reduce the gain fwiw. But I will for sure socket mine and build it stock first.

So, I had some questions regarding the flabulanche and some modifications I wanted to make. I noticed that ROG made a "high gain fetzer valve" (the omega circuit) which I was interested in not so much for additional gain but rather for the variable input loading - additionally I wanted to move the gain control from between q1 and q2 to the source of q2 - the idea is to essentially convert the flabulanche to a cascaded boost festival.

I want to add input loading to the flabulanche to make the volume knob cleanup as righteous as possible. I know it's great already from the videos but I want to experiment because I'm weird like that. In no particular order:

1. If I use a mpf102 in q1 and feed the circuit 24v, can I substitute a fixed value resistor to ground for the gain pot, and add a potentiometer to q2 to adjust the gain via q2 bias (like the fatpants does)? Or would that be too much gain? I want light clipping at noon on the "gain" (slash fat) control.
2. If I add the omega input impedance control, will I need to change the rest of the cascaded fetzer part of the circuit to a higher resistance? (For example, using 50k trim pots on the drains). I ask because the omega article seems to imply that it's specifically sensitive to changes in input impedance - so I was curious is the high circuit impedance (pre-buffer) is necessary to get the most out of the "range" control.
3. if I wanted to implement a 'body' switch, should I just wire another cap in parallel with C2 (and a 10m resistor between the two) and use a spst switch? (again, like in the fatpants) Or should I add this to Q2?
4. If I use higher resistance drain trim pots, will I have to change the source resistors? Or will 470 work fine?

Thanks in advance for any help, I'm going to try and answer these questions myself through research in the meantime.

Somewhat related to this, I have a question - in the build doc it mentions using a j201 in q2 for more gain, if desired. If using a j201, would you use a larger trim pot? Say 50k? I imagine you'd also use (ideally) a 1.8k source resistor? And if so, would the bias point remain the same for q3?

I also have a question about incorporating a fender-style NFB presence control in the 'power tube' (mosfet) stage but I fear that's a little too far off topic for this thread.

That mu-valve looks like the one on the former Thor circuit over at runoffgroove (replaced by the thunderbird) and the booster part of the Paul Cochrane fat boostered if I'm not mistaken.

I don't know very much but the Thor (and the jfet Vulcan by Joel davisson) use a similar layout for q1 and q2 (where q2 is primarily the gain providing transistor if I'm not mistaken, which is totally possible and indeed even likely) to Jon's snow day overdrive (and the ROG umble now that I think about it, but of course these all use differing bias and cap setups).

Because of the bjt buffer at the end of the circuit I've wondered myself if one could make a higher gain version similar to cascading the ROG omega into two other fetzer valves but I don't know enough about the MOSFET section to know what other components you'd need to change. Or even if it would sound good or like a hot mess (the omega is a 30-35db boost so I imagine you'd get a ton of overdrive including hard clipping from the fets unless the gain was way down)

You can still see the Thor circuit at http://www.runoffgroove.com/thor.html even though the link isn't on the main page any more from what I can tell.

As far as the mu-amp as a gain stage, I mean I'm sure it's possible I just wouldn't know how to be honest.

The beautiful thing about the snow day tone stack is how simple it is - if you want to add a more traditional b/m/t toneatack you'd have to do it right after q1. From the schematic it looks like there's a cap for treble bypass but other than that not a whole lot in the way of stuff.

So I've spoken long enough - I'm sure Jon or Brian will answer the question instead of just contemplating how wonderfully versatile this circuit can be.

Awesome build - I didn't realize you could run the dirt baby on 18v.

I'm now waffling between the dirt baby and the 1776 multiplex...

After watching the ehx freeze this is very relevant to my interests....

It's just such a cool effect. I need to see where I can get one come April.

I won't have any real time until March of this year to work on projects, but so far I've been really happy with this place. This is a much cheaper hobby than working on my car lol.

By way of suggestions, I used to be part of a car forum and there was a "lounge" area that was like a big group chat where you could go to ask a quick question, and if someone was there they could answer it. It was mostly for off topic shooting the breeze kind of stuff though.

As far as technical information goes, this place is awesome. I need to spend more time here and at diy stompboxes though because I still have a ton to learn.

Looking forward to a great 2015, and specifically the fat pants Jr.

One last bump to avoid making a new thread.

So, I'm listening to midwayfair here - I don't have a ton of time to teach myself how to properly bias a Jfet (i.e. what values you need to make a 'fat' and 'range' control work on the same transistor) so I'm just going to slap together the Omega and the Fatpants design/circuit but with 2 changes - (1) I'm using an MPF102 as a shared buffer between the high impedance Omega side and the lower impedance Fatpants side, (2) I'll use the 10ka "master" control of the omega as a sort of "gain" control to overdrive the J201 in the fatpants.

Of course, there are 3 controls that will affect the gain of the circuit, so even with the 'pre' knob maxed you can still dial it down with the 'fat' or 'range' controls. It's just that the 'pre' is the most obvious one.

It will be a true bypass pedal so I don't have to worry about how to make the buffer (which is in the middle of the circuit) switchable.

Thank you Midwayfair for your help. I know I seem silly for trying to go about designing a circuit without first learning the basics of transistors, so I thank you (and the rest of the forum) for bearing with me and taking the time to explain to me the folly of said attempts.

I'm not trying to recreate any specific thing about any specific circuit, so I realize that 7v is an important number, but I was planning on (1) running the whole circuit at much higher voltages (18v)

Well, you'd put it at 14V if you wanted to keep that part the same. The drain voltage changes how the waveform clips.

and (2) have Q1 function as a kind of a clean preamp/tone shaper for Q2. I had originally wanted to use the tone stack from the Umble right after Q1 (which in that case would have a fixed bias because that would be way too many knobs for me haha) and then experiment with a volume control after Q1 to figure out a good resistor to use to limit the current going to Q2 (which I wanted to use a J201 for).

What you're describing in a sense completely alters the circuit. In fact, you can't even use the devices as described and it no longer really makes any sense at all to use the omega circuit for what you've described.

A quick recap on what the Omega is doing is in order. It's mimicing a treble booster that used a germanium transistor, high gain, and heavy input loading. The circuit is DESIGNED to clip, and in a particular way, so using it as a "clean preamp" wouldn't be good. It's designed to create a heavy load on the pickups to reduce the treble from the input device, which makes the distortion created more pleasant. Together with the bass cut from the input cap, the stock circuit creates a peak at about 1KHz (coincidentally right in the "hole" in a Vox amp's tone circuit, which is why they were a match made in heaven); the range control adds more bass, up to a point. Any tone control you put after it is going to be nerfed by the overall design of the circuit, which is cutting highs and bass and creating a big midrange peak. If you correct the input loading and remove the bass cut, you might as well just use the FETzer valve, which is a simpler circuit and can be full-range.

Sorry, I wasn't specific enough about it - I had contemplated two alternate designs. Were I to use the umble tone stack, there would be no range control; in that case I agree something like the fetzer valve would be more appropriate.

Additionally, the J201 is a poor choice for a clean preamp because it has very low input voltage headroom (under a volt, sometimes as little as half a volt). FETs are either lots of gain and low input headroom or very little gain and lots of input headroom. It's one or the other, and it doesn't matter what your supply voltage is. If you need a clean preamp, there are better devices to use. We use FETs because they sound better when they clip than other options.

I had planned on a two transistor design - Q1 was to be a very low output transistor (MPF102) and Q2 was to be a high output (but low headroom) transistor. For the prototyping stage I had planned to use a potentiometer as a "volume" control to determine what resistor I would need to keep Q2 from overdriving too much.

Continuing, Q2 is more than just a source follower. (As a note, you can also use an NPN BJT in that spot without any changes and it'll be lower noise.) You mentioned using a J201, but I think that device won't even work in that spot the way it's set up; the gate would be referenced to your positive supply rail and not ground. I'm not totally sure about that but I think at best it might sound strange, but it will also very definitely clip if you put a FET there after all the gain coming from Q1. You also will lose a huge amount of gain from Q1 if you change how the circuit is set up. Right now the circuit has a gain of over 30x -- if you decouple the two transistors, even running on 18V and using a J201 (the highest gain JFET) you won't get that much gain.

...
I really don't understand what you're describing here or how it applies to this circuit. Depending on which leg of the gain control you jumper, on the distortion side you either turn it into a pure gain control (it doesn't attenuate the signal into the gain section, but it's still varying the gain, and it doesn't change anything about the treble) or you turn it into a variable low-pass filter and remove all the gain from the distortion section, which probably wouldn't sound like much of anything. On the clean side, you're varying the gain of the third op amp stage rather than making it a voltage divider, which isn't really any different except that you'd remove the ability at the highest gain setting to dial out the clean completely. Any effect it has on the treble is incidental because of the reduced gain. (And the klon already sounds less trebly when you turn up the gain ... or turn down the treble control, which is doing the same thing as varying the gain coming from the clean side.) In any case, I can't see how that applies to the omega. You haven't described anything that would create a treble cut, and you'd need to add more devices to create a clean blend.

I wrote up something real quick to show what I'm talking about, which I've attached. It's missing capacitors and resistors pretty much everywhere but it's to give a general idea of what I'm talking about. R1 and R3 (the two variable resistors) are supposed to be tied (they represent the two levels of a 100kb dual ganged potentiometer)

I really should upload the image but I've already spent way too much time on this post. I'll try and do it later today though.

...

Again, the "Fat" control is essentially unworkable in the Omega. It's doing exactly the same thing that the trimpot in the Omega is doing, but you won't get any sound throughout part of its range. And the "range" control IS a bass control. It sets the high-pass filter with the input cap. I'm also not entirely certain why you want to use the Fatpant's gain control. What specifically does it do that you're trying to achieve? You also say you want a fixed bias -- again, re-read what I wrote about the Fat control. It's a bias control. Its effect on the EQ is collateral damage.

Again I wasn't clear enough. Here are the two separate circuits I'm talking about:

(1) umble tone stack. No range control, no fat control. No changes from the Umble schematic on the ROG website until the "volume" potentiometer.
(2) Omega-based. Range control + limited 'fat' control.

I really do appreciate you bearing with me. I can be all over the place sometimes.

...

Honestly, I don't think this is really a useful way to think of things. In a transistor circuit, for the most part you're just changing what the circuit amplifies. You can tell the circuit not to amplify all the frequencies by using negative feedback and bypassing the source, but in a circuit with only a couple devices, how different is that really from just cutting some frequencies before or after the active device? Let's take the source bypass capacitor as an example. Depending on how big the capacitor is, it either makes the transistor amplify all frequencies, or it makes it amplify all frequencies except some bass frequencies. Just because it's "technically" an active filter and "boosting" certain frequencies, how different is that really than cutting the bass before it gets to the transistor and then amplifying what's left? You still pick a frequency to set as your -3dB cutoff, and the filter is still 6dB/octave just like any passive single-pole filter. They're functionally identical in a circuit this simple.

This is what I needed to hear. For some reason I had gotten it into my head that there was some kind of difference in fidelity depending on where in the circuit the tone control is. Clearly there's no appreciable difference so I'll just go with the umble tone stack rather than try and figure out using the range and fat control in conjunction with one another. In my head the fat control would have functioned kind of like a "timbre" control where you can affect the girth or character of the frequencies determined by the range control.

If you were working on a circuit that didn't use a source bypass capacitor, adding one to make a high-pass filter would make a pretty substantial difference, because then you'd have a gain control that also cuts bass if you want. If you were working on a circuit with several amplifying devices and could devote each device to one EQ task (this one boosts just the bass, this one boosts just the treble, etc), then there would be more sense in discussing the benefits of active vs. passive EQ.

Again, I needed to hear this. As a conceptual matter I wanted to use the range and bias controls to adjust the circuit for different guitars and amplifiers. I don't need a 6-band EQ but I wanted something a little more versatile than a "tone" knob.

At the top of the bias/fat/timbre control I wanted to induce some very mild clipping in Q2 but the primary source of the clipping would be the diodes following Q2. Obviously in the schematic I'm missing a few capacitors that would follow the clipping stage.

All I'm really trying to say is that you're asking a lot from the Omega. It's got two transistors in it, but you really need to be thinking of it as a SINGLE amplifying stage. That really limits how much cool stuff you can squeeze out of it.

See this is where I got tripped up. I've looked at different designs - the umble, the peppermill, the omega, the King of tone, the sun king, the kingslayer, the marshall bluesbreaker, the jfet vulcan, etc etc etc and thought that it would be feasible to design a really simple, two transistor OD pedal (with diode clipping) and a kind of "familiar yet new" tone circuit. I love the sound of my fatpants with my bluesbreaker/PoT clone, but I really want to split the fatpants in two and put the buffer before the OD pedal and the boost after. Kind of like literally every other two switch distortion/od pedal out there does, but with a discrete circuit instead of using op-amps.

Thank you so much for the in depth explanation.

I'm not trying to recreate any specific thing about any specific circuit, so I realize that 7v is an important number, but I was planning on (1) running the whole circuit at much higher voltages (18v) and (2) have Q1 function as a kind of a clean preamp/tone shaper for Q2. I had originally wanted to use the tone stack from the Umble right after Q1 (which in that case would have a fixed bias because that would be way too many knobs for me haha) and then experiment with a volume control after Q1 to figure out a good resistor to use to limit the current going to Q2 (which I wanted to use a J201 for).

When looking at the omega, I thought "hey, that's a brilliant idea" and I thought it might be cool to have a "tone stack" that alters the parameters of the circuit rather than just roll off certain frequencies. So does the range control affect both the treble and bass? If that's the case, with the "fat" control primarily affecting the midrange character, they could coexist within the same pedal if (1) I did the necessary calculations to find appropriate source and drain resistors, and (2) didn't care about the 7v bias that's characteristic of the rangemaster. I remember in the article they said a 5v bias was 'fatter' so I feel like it's an idea at least.

I wanted to use Q1 as kind of a preamp, with an MPF102 and the aforementioned 'range' and 'fat' controls, and then use a dual ganged pot in connection with Q1 similar to the gain/clean you find on the Klon, but where the "gain" control is just a variable resistor controlling how much current two clipping diodes see. So, kind of a character pedal vs. one with a traditional tone stack.

Again, thank you. Clearly I have a lot of reading (and math) to work on.

Can you adjust frequency response (for example a bass rolloff circuit) by varying the resistors/capacitors on the source prong of a Jfet?

I ask because I'd like to add a potentiometer in conjunction with the "Fat" control, instead of a body switch, to adjust the frequency response of a JFET boost. I've been looking at the ROG Omega and I became curious if you could add a 'fat' control (q1 gain like in the fatpants) and something like a 'body' control but lower frequency so that it acts like a bass cut (I don't know if you'd be able to boost bass or what have you, I'm just spitballing really because I just watched a youtube video on how to calculate the gain of a transistor and I was completely lost.).

Obviously this wouldn't be a true treble/mid/bass tonestack, just a way to implement a similar functionality by adjusting the input impedance ('range' on the ROG), gain ('fat' on the fatpants), and whatever affects bass response. The overall goal for the pedal would be an always-on low parts count tone shaper/conditioner/enhancer with an output buffer. Maybe as part of an OD/Dist/Fuzz pedal eventually, I don't know. I'm mostly curious as to whether this is possible.

As always, thanks for any and all replies.

Okay, so I know you guys are tired of seeing this bumped up to the top of the heap and I promise this is the last one.

I finally got everything working - don't know what caused the volume pot treble roll off but after I uncrossed some wires coming from the fat control everything seems to be well sorted.

I can't tell if the body switch works - on either setting there's scratch from the fat control - but I don't care because the sound is amazing.

Seriously I can't even begin to explain how good this pedal sounds. I had today off so I had some time to fiddle around with it and every setting sounds good. From unity boost (which is actually only about 10-11 o'clock depending on where I have the fat control set) to pushing my little 18w combo over the top, this little guy is electricity underneath my fingers. My clean sound has never been so good and the distorted sound is deliciously complex and 3d. I can't say whether or not I like this + my amp's distortion better than my Mythical Overdrive (bought in a moment of weakness, if I had more time/diligence I would have gotten the Sunking II which I still might do) yet but this pedal is definitely staying on my board in one form or another. Still have to get a 12v adapter but for the time being this runs great off of 9v.

Thank you to everyone for your help and I look forwards to reporting on a bloviator build and a bacon bits build sometime in the coming weeks. Also an 8ball build and two other secret sauce builds for friends.

So, update. The problem was caused by the output jack - apparently I got solder on it and connected the two terminals, but everything else was okay.

I have a new problem - there's a pronounced treble rolloff when I turn the volume down (even more pronounced than on a guitar before you add a treble bypass cap/resistor). I imagine it's because I have the volume pot wired incorrectly? Right now I just leave the volume all the way up and use the fat control to adjust volume but that's hardly a perfect solution. Even with the fat all the way down the volume boost is pretty intense. At first I had it wired with the one outer lug to ground and the other to hot with the middle lug wired to the effect output, but before I got it working again I changed it back (middle lug to output, one to effect and the other to ground).

What I may end up doing is wire a treble bypass cap+resistor just so I can keep the volume below all the way up and have it not sound like I'm playing underwater.

Other than that small problem though the pedal works as advertised. Like taking a blanket off of your speakers - just comparing the T/B sound with the Buffered sound is really eye-opening. Honestly I kind of like the buffered sound more than the sound with the effect on - in the future (knowing what I know now) I may build another one of these and use a different Q2 than the J201. As a buffer/solo boost it's perfect for solo lines (what I previously used my heavily modified SD-1 for) - adds some mids and thickness according to your preference and really makes solo lines stand out.

Other than that I also have a few od/boost related builds on the way (8ball, Bacon Bits) so I should report again once I get all the parts for them (turns out I needed a few more caps that what I got from mouser).

Thank you all for the help and support.