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Post by asmith on Aug 27, 2020 17:53:01 GMT -5
Background:I bought a bundle of things to save money on the bundling. One of the things included was a Boss BD-2 Blues Driver. And I'm in luck: it's an old mod-able release.I also recently bought a Marshall Super Bass Mk II 100-watt amp head. Childhood dream: realised. The Marshall pleads to be overdriven ("driven over?"). I want to use my BD-2 Blues Driver as an optional extra gain stage before the amp, to push it into saturation sooner. But the BD-2's stock sound is... eh. Its "clean" boost is quite good. I find its gain unpleasant — even at the low levels I'd use. It's too 'ice-pick' fuzzy, and it seems to squish the signal's frequency range. I already have a beautiful S.D. TweakFuzz that Newey gifted me many moons ago (thanks again Newey 🤗), and a Big Muff Pi also came in the same bundle as the BD-2. My fuzz needs are catered. So: I want to mod the BD-2 to change its gain character from ice-pick fuzz to saturation and warm clipping — and to otherwise improve its sound in any way.I've googled over a few mods. I'm impressed with what JHS has done with their "Blu-Drive" mod. It sounds somewhat more "transparent" — a nauseating term, but in this case perhaps an accurate one. Here's a video of the stock BD-2 next to a JHS-modded BD-2. I can't find a schematic for that JHS mod anywhere, which is obviously good business sense for JHS. Worse, I remember very little of whatever electronics knowledge I picked up back when I posted here, a decade ago. So, I'd like to ask for GN2's help and recommendations modding the BD-2 circuit.
I found a circuit schematic. And here's a schematic of a clone, with helpful component labeling. I'm unsure of the clone schematic's fidelity to the original, but it was used in this PremierGuitar article. What would you do to the BD-2, to fix its fuzz, and improve its general tone?
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Post by thetragichero on Aug 27, 2020 23:06:22 GMT -5
hey! i just got one too! (had the wazacraft one briefly before that because i got it for the same price as a used regular one, flipped it)
just so happens i just modded mine (for use with my bass vi)
there's a decent premier guitar article by Brian wampler that walks through the circuit a bit although a resistor or two is labelled wrong
c26 to 470pf
r38 to 33k
c34 to 22nf
(if you find it too fuzzy/bassy after the other mods you can lower r50 from 1M to... 470k 100k 10k. whatever really)
this whole section stock is like a fender tmb tone stack. those mods give some more marshall-y values
d10 to led
d9 to led with 1nf cap in parallel
(these provide assymetrical clipping and louder output to half of the waveform along with the cap smoothing some of the high clipping frequencies)
c17 to 1nf
c18 to 10nf
(c17 and r25 are a treble peaking circuit. this raises the cutoff past anything useful. could also remove c17. basically both of these cut super high stuff)
c9 to 2.2nf
(this section is a gyrator that stock is centered right at 120hz. i bet it gives some body to a thin and but shouldn't be a problem for you. this change gives a broader mid hump around 600hz. could've tweaked it more to get a tubescreamer-like 720hz but I'm fine with simple)
d1 to a fet (or just leave it)
d3 to led
(these aren't clipping sides per se but will change the character of that op amp stage)
c101 (it's on the daughter board with two pots on it) to 47nf
(makes tone control more useful)
all these together cut a bit of low frequency content on my bass but i found that to be desirable. you may not even notice on guitar
tested on the traynor yba1 so quite similar to what you're planning to use it on
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Post by thetragichero on Aug 28, 2020 13:34:00 GMT -5
still tweaking. a little too much bass cut. right now r50 100k c9 1nf c16 560nf. needed it for tonight to work with a sansamp/di so it's different than if it were going into a big amp here's a gyrator calculator if you wish to fill around with that section: www.muzique.com/lab/gyrator.htm |
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Post by JohnH on Aug 28, 2020 18:34:12 GMT -5
Hi asmith, I like doing that sort of thing too.
I tried a bd-2 in a shop, compared to other Bosses like Sd1 and Od3. Bd2 had a nice clear transparent low range, as you say, getting a bit fizzy-fuzzy at higher gain. I got an Od3 that day.
I also got and Sd1 and a Guv'nor2, for modding. After doing the research such as you have done, I found a lot if insight from modelling the circuits in Spice, which allowed me to bend them to my wishes by checking out mods. So doing that would be my suggestion for the Bd2.
As for the Bd2, it's kind of a quirky circuit, it doesnt really follow any of the generic types, like it was designed by trying out 'what happens if I do this?', on a relaxed Saturday afternoon with a couple of beers.
To tackle the fizz, id guess its generated around the group of four diodes. If that's true, then I'd try doing things like:
Adding a resistor in series, with the whole group or just one side, or a
cap in parallel.
or adding another diode on one branch
Have fun! Before and after clips please ..
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Post by asmith on Sept 2, 2020 15:10:14 GMT -5
We can be Blues Driver Buddies! there's a decent premier guitar article by Brian wampler that walks through the circuit a bit although a resistor or two is labelled wrong Right? And also the circuit he's using is labelled "Clone," and is this circuit ( i.imgur.com/8cds1RV.png ), which is definitely not this circuit ( i.imgur.com/lAfVP4a.png ), which is labelled "Boss Blues Driver." When you modded it, did you find that the "Clone" circuit was accurate?And thanks so much for all the details of your mod. I'm going to take John's advice and model up the existent circuit in a spice program, implement your changes, and see what happens. This simply requires that I relearn spice. Hi JohnH! To tackle the fizz, id guess its generated around the group of four diodes. If that's true, then I'd try doing things like: Adding a resistor in series, with the whole group or just one side, or a cap in parallel. or adding another diode on one branch I will try this once I've modeled it in spice. Before and after clips please Ah, well, we'll have to wait until I get my hands on a cabinet for this amp head then. As for the Bd2, it's kind of a quirky circuit, it doesnt really follow any of the generic types, like it was designed by trying out 'what happens if I do this?', on a relaxed Saturday afternoon with a couple of beers. Ah. So, I'd like your (and others) opinion — and I've no idea whether this next question is idiotic or not because my Googling has been fruitless thus far. Which parts of the circuit can I tweak, and in what ways should I tweak them, to increase the harmonic saturation? I don't want to merely boost and clip, if that's what the Blues Driver currently does (?). If possible, I'd like to add rich overtones (also if possible, second order harmonics specifically) that are IMO more than half the reason everyone likes a good tube amp crunch.Thanks for the continued help. |
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Post by JohnH on Sept 2, 2020 16:01:40 GMT -5
Cool! Im just not sure about this one, but, I do know that jfets can be the basis of a really nice tube-like saturation, and Ive worked up OD boxes based just on those. So armed with a Spice model, id be looking to explore how to get the jfets to do more of the distortion instead of the diodes.
Here's a theory I have about distortion boxes etc:
In a given chain of amplification, from guitar to speaker, there's a chain of many amplification stages that all start clean with very small signals and as the signal rises, they start to distort according to their characteristics, soft or hard. The stage that is most dominant in the final tone is the one that starts to distort first. This could be anywhere in the chain depending on the signal levels at each point. So within the BD2, try to find that and focus there, and maybe if it turns out to be the diode stage, try to tweak it back more towards the hottest jfet stage. Or try to get stages to balance so they all drive at the same time.
Everything else is 'tone shaping' rather than 'tone creation', and that will be the next port of call. Tone shaping you can investigate in Spice using the usual frequency sweep response analysis. These runs are all 'linear' being based on the response from very small signals (even if the numbers are big), they don't capture distortion. So youll need a transient analysis for the distortion testing, feeding in sine waves of set frequencies to look at wave forms at various places through the circuit.
Another couple of tricks I learnt with jfets:
A jfet stage likes to be biased to give an output voltage just above mid supply voltage, to maximise its available swing. and even of a given type, they are highly variable and need tweaking based on individual examples. So you might test the real dc output voltage from each jfet stage in your example and see if it is in the middle range of dc volts, then you might adjust its biasing to balance it.
Also, when a jfet starts to distort, it can clip softer or harder according to the current running through it. A bit more current (eg with smaller source and drain resistors), and biased accordingly, leads to a softer distortion.
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Post by Yogi B on Sept 2, 2020 16:12:28 GMT -5
there's a decent premier guitar article by Brian wampler that walks through the circuit a bit although a resistor or two is labelled wrong Right? And also the circuit he's using is labelled "Clone," and is this circuit ( i.imgur.com/8cds1RV.png ), which is definitely not this circuit ( i.imgur.com/lAfVP4a.png ), which is labelled "Boss Blues Driver." Well they look pretty similar to me, it's just that the second contains a bunch of extras: input & output buffers, and trio of additional FETs used for bypass switching as controlled via the BJT flip-flop in the lower right. |
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Post by thetragichero on Sept 2, 2020 17:37:41 GMT -5
most folks that clone boss pedals leave out the buffers and switching anyway
man boss was incredible with single-sides pcb designs
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Post by ashcatlt on Sept 3, 2020 12:30:24 GMT -5
So there’s no such thing as “adding harmonics”* without boosting and clipping. That’s literally what distortion - all distortion - is: a circuit trying to produce an output voltage that is outside the limits of how much it can produce. The transistors have limits “naturally” built into them, and the diodes can kind of be seen as “artificial” limits, but in the end the way the signal is affected is pretty darn close to the same given that you try to exceed the limit by the same amount.
That is to say that as much as people obsess over clipping curves, they are actually pretty much the same once normalized, and any measurable difference between them will not be much if at all actually audible or even “feelable” when playing into it. Yes, I’m saying that the harmonics “produced” by a JFET trying to swing to 18V on a 9V rail will be damn near identical to those “generated” by trying to push 1.2V across a silicon diode-to-ground with a 0.6V forward voltage, the same as 0.6V across a germanium diode, the same as 500V from a tube running off a 250V rail. The differences in the curves literally don’t matter enough to worry about.
I’ve messed with a lot of different clipping curves through the years - opamps, diodes, tubes, transistors, clamped sine fictions, atan and tanh and exponential and power laws, even true discontinuous hard clipping. Now the real digital hard clipper is noticeable uglier at “low gain” setting where the signal only just barely or occasionally tries to pass the limit, but even this one when driven hard enough starts to converge to the others, and the differences between any two decently behaved curve are so small that I don’t think they matter enough to even really bother with.
What does matter?
1) How far past the limit you’re trying to go.
B) How symmetrical the limits are with respect to the signal’s rest point.
III) Tone shaping on either side of the clipping section. I’d argue that this is the most important part of really changing the sonic character of any distortion circuit. What goes in has a huge impact on what comes out, but very often what comes out needs to be compensated, shaped, or limited. You can get a lot of mileage from messing with “pre-emphasis/de-emphasis” filtering.
I don’t have any experience or specific suggestions for this circuit, but if we’re bugged by fizz we should either not send quite as much high frequency content into the clipping sections and/or (probably and) knock down the high-end that was “generated” after.
*I have a real (if somewhat pedantic) problem with the common language that talks about distortion adding or producing or generating harmonics. Distortion doesn’t add anything to the signal. In fact, it only really takes away. It gives us less voltage than we would expect from a linear system.
You can make distortion sounds by additive means. Make a copy of your signal and shift all of the individual frequencies up an octave and then mix it with the original. Keep doing that up the harmonic series and you theoretically will end up with a combined waveform that looks a lot like one that was actually distorted. There are digital things that do this, but they’re never very satisfying for much the same reason that true additive synthesis never really took off (organ-type things not withstanding).
That reason is that the frequency spectrum is actually an analog thing, a continuous “line” made up of an infinite number of infinitesimal points, but no circuit or code can actually analyze and shift an infinite number of points, so you end up having to sort of quantize it into a finite number of bins. That’s fine for an organ because it’s got a finite number of possible starting frequencies (the keys), but a guitar can and does fall in between those bins. All you have to do is envision a bend or even vibrato.
But we’ve gone a little beyond my main point which is that actual distortion doesn’t work in this additive way. It doesn’t generate multiples of the input frequencies and add them together. It just brute force changes the shape of the wave in such a way that it approximates (perhaps more properly “can be approximated by”) one that contains that set of harmonics.
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Post by asmith on Sept 13, 2020 7:42:18 GMT -5
I'm responding to each thread response first. Follow-up questions and important comments are bolded. After, I continue the discussion. Thanks again, everyone. ------------ Cool! Im just not sure about this one, but, I do know that jfets can be the basis of a really nice tube-like saturation, and Ive worked up OD boxes based just on those. So armed with a Spice model, id be looking to explore how to get the jfets to do more of the distortion instead of the diodes. Great. Thanks for this insight. This makes sense to me. Understood in principle. How would I actually do this on the BD-2 circuit?I'm going to give it a go. It's been forever since I ran a Spice simulation — I'll likely have more questions and might ask for my hand to be held.
And I'd do this by adjusting the source and drain resistors to get the output voltage in the middle of the supply voltage?Excellent, thank you. Well [the circuits] look pretty similar to me, it's just that the second contains a bunch of extras: input & output buffers, and trio of additional FETs used for bypass switching as controlled via the BJT flip-flop in the lower right. Ohhhh. I see that now. Thanks. most folks that clone boss pedals leave out the buffers and switching anyway man boss was incredible with single-sides pcb designs Right! Taken into consideration. So there’s no such thing as “adding harmonics”* without boosting and clipping. That’s literally what distortion - all distortion - is: a circuit trying to produce an output voltage that is outside the limits of how much it can produce. The transistors have limits “naturally” built into them, and the diodes can kind of be seen as “artificial” limits, but in the end the way the signal is affected is pretty darn close to the same given that you try to exceed the limit by the same amount. Thanks for the clarification. This prompted some further research, so I went and did a bit of reading and have come to understand it more. Thanks. Really? I thought that different components "clipped" — reached the limits of their output — in different ways. I.e., some components somewhat gradually dampened their output as they approached their voltage limit, like a car braking harder the closer it gets to a wall, and other components simply stopped when they hit the limit, like a car smashing into a wall. And people like the "compression" — the metaphorical braking — that results from components that output a signal like this:  And they favour that over the harder, fuzzier, not "compression" but just "clipping" that results from components that output a signal like this:  What I wanted to clarify when I said that I didn't want just boosting and clipping was that I wanted an output signal that was distorted somewhat more like the first diagram than the second. I say somewhat because obviously, I'm not actually using tubes. And, some of the hard fuzz is nice: I think it sounds like a speaker cabinet reaching its limit. I get that. I'm not looking to drive anything hard enough, though. Understood. (I chuckled at 1, B, III.) Alright! Thanks. I get where you're coming from here. In common language's defence, I think people talk about "adding" because they mean it adds harmonic "information" to the signal that our ears appreciate. If I see a Renaissance painting with a flamethrower hole in it, then yes, the artwork itself has had parts of it taken away, but the effect and story the artwork imparts on me has certainly been "added to." ------ Next steps. I have modeled the circuit in KiCad, a program that contains a Spice simulator. I didn't bother modelling the input and output buffers, BJT switching or power supply (thanks again for the clarification, Yogi). It's basically the same circuit as the Clone diagram.  I originally started modelling everything, but then realised that the capacitance units weren't defined in the BJT switching section in the original schematic, so I gave up. That's why resistors R2 to R6, capacitors C1 to C3 and transistors Q1 and Q2 don't exist. Sorry. I'd like to use this diagram and its labeling only, when referring to circuit components in the future.Where are my thoughts now? I'd still like to:1. Soften the fizz/fuzz from what sounds on YouTube demos like "hard" clipping, to softer clipping. As JohnH notes, this may require tweaking the circuit to let the JFETs do more of the distorting. And maybe I use LEDs instead of the 1N914 diodes that are currently in there. 2. Perhaps change the clipping from currently symmetric to asymmetric, to induce more even-order harmonics. Here's an image that shows my rationale on asymmetric clipping providing even-order harmonics:  And here's a YouTube video that compares even harmonics with odd harmonics: New, fun thought. As I said, I own other fuzz pedals. Modding a Blues Driver to output a little gritty subtle overdrive instead of the Fizz-Fuzz it is now would be nice, sure. But really, for overdrive, I could buy a KTR, a Schaffer Replica, and a Behringer Vintage Tube Overdrive, and be very happy. (OK — maybe a Lovepedal Eternity, too.) The whole point of this pedal is to push it into a Marshall that's already breaking up. Instead of an Overdrive circuit, what I've lately been thinking about is turning this Blues Driver into a Harmonic Sweetener, also known as an Aural Exciter. See, I really like what a Harmonic Sweetener / Aural Exciter does. An Aural Exciter subtly distorts the high frequencies of a signal, and then mixes them back into the dry signal. Here's an YouTube video that shows what a simulated Aural Exciter can do to a clean guitar sound (although the guitar is acoustic): (If the time-skipping feature isn't working on your computer, skip to 1:45 to hear a "dry" Acoustic Guitar sound, before the YouTuber engages the simulated Aural Exciter at 2:12, and then begins to switch between bypassing and engaging the effect at 2:47.) I'd be excited to turn the Blues Driver into a Clean Boost with a dial-in Aural Exciter (aka Harmonic Sweetener / Aural Sweetener / Harmonic Exciter / Sore Moronic Sex Whitener) feature. Here's a schematic by Jules Ryckebusch of his own "Harmonic Sweetener" circuit that produces this effect:  I can see that in my Blues Driver (scroll back up to the schematic), I have: two Gain Stages; a set of Clipping Diodes in between the Gain Stages; and a Summing, or Buffering, OpAmp (if I'm correct in thinking that's what it is). The Harmonic Sweetener boosts high frequencies through a four-OpAmp gain stage, and one of the OpAmps has clipping diodes in it. So in my head, I could do a little jiggery-pokery with the Blues Driver circuit with some wires and a soldering gun, and simulate some of this functionality. I imagine I can: 1) Swap out C4, 100nF, for a smaller-value capacitor that only lets higher frequencies through, 2) Route some of the input signal to the "1" input to the OpAmp 3) Remove C17 and use the 10k Lin "VR2" Tone pot to control how much of the gained-and-clipped frequencies hit the OpAmp, and 4) Move the "VR3" Level pot to after the OpAmp, to use as a general volume pot — or would this better be placed in the OpAmp's feedback loop somewhere? Then, I'd have a Clean Boost pedal, in which the Gain control distorts the high frequencies, the Tone control decides how much of that distorted high end is blended back into the signal, and the Level control simply controls the Level. Then, to soften the distortion, I could: 5) Change D2 to D7 for LEDs with softer clipping, 6) Stick a resistor between D4 and D5 to make the clipping more asymmetric, and then 7) Further play around with the JFET gain stages to play with the clipping there. What do you think? Is this feasible? |
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Post by ashcatlt on Sept 13, 2020 11:39:42 GMT -5
The op amp at the end isn’t really summing anything because there’s only the one signal feeding it to begin with. It’s actually doing some makeup gain and some tone shaping. I think it’s actually something like a speaker simulator, but that gyrator configuration is a little above my paygrade. But I was looking at it going “How can that even work? It’s not biased above ground”, so I went and looked at the “original” schematic and that doesn’t have any bias on the op amp either, but then I looked at the clone schematic and it actually does. I think the “original” is wrong in this case, and you have dutifully recreated their mistake. Probably wouldn’t be a huge deal in modding the pedal because it’s already built correctly, but... We don’t usually use a non-inverting opamp stage as a summing mixer for a couple of reasons, though I’m not sure how relevant the are here. One issue you’re going to have in trying to feed the signal from the input (after the buffer, please) to somewhere at the end of the circuit is that you’ll also be feeding the output of the circuit back to input. Notice I said “feed” and “back”.  That could be cool, but maybe not what you want. It really would want another buffer to isolate the split point from the output. And mixing resistors of course. Now you may have seen people talk about “hard clipping” vs “soft clipping”. Hard clipping is what I talked about above, the signal tries to exceed the limit, but can’t, so just flatlines. If the opamps (and there’s three of them here, two of them are disctretized - basically built from scratch) clip, that’s hard clipping. The diodes to ground are hard clipping. Soft clipping is when the limit isn’t actually a limit, just kind of a knee in the curve. The classic example is a Tube Screamer where the diodes are in the feedback loop of the opamp gain stage. They look like an open circuit for smallish signals so that the gain is controlled by the variable resistance that is parallel to them. When that gain multiplied by the input voltage is greater than the forward voltage of the diodes, though, they go to something that looks like a short across that pot, and gain goes to unity. The signal is still allowed to wiggle, but it’s not as much bigger than the input as the smaller signals are. Well, but actually it’s not exactly unity, it’s more like unity gain (x1) plus the forward voltage of the diode. This looks, works, and sounds almost exactly like mixing the clean input with a hard clipped version of itself. So if all you do is mix the input with the output, you kind of end up with a funky TS kind of thing. But yeah, if you cut most of the low end out of the hard clipping path, you would have something like an aural exciter. You talked about putting a resistor in series with one of the diode pairs. Well, you said “between”, but it really doesn’t matter where you put it, it will work out exactly the same, and actually it works pretty much exactly the same as the soft clipper we were just talking about. The limit becomes kind of squishier. If the diodes look like straight wire, then without the resistor it’s a short to ground - you get a flat line output. With the resistor, it’s a voltage divider - you get an attenuated version of the input. If you do that only with one pair, it will also make the whole thing asymmetrical because you’re doing different things to each side of the signal swing, but it’s not really the same as asymmetrical hard clipping. If you want asymmetrical hard clipping, you’d take JohnH’s hint about bias and just go the other way. Deliberately misbias the thing so that it hits one limit before it hits the other. Or you make the total forward voltage for one of the diode pairs bigger than the other. That (asymmetrical diode to ground) doesn’t always work the way people expect it to, but in this case it actually might. Since we’re talking about bias, no don’t mess with the resistors around the individual transistors. Like I said, those are set up to work together as an opamp, and changing just one of them will probably through that out of whack. I guess I’m not sure what would happen, but like any opamp, those stages are biased at the input by way of the resistor coming from the bias voltage point. That is the voltage you’d want to adjust in order to move the operating point for either more or less symmetry. How you do that kind of depends. You could just change one of the resistors involved in the bias voltage divider (which is not shown in your schematic) to throw all of the opamps off center, or you could work a voltage divider in between that bias point (which is the output of the opamp in the power section) and the resistor that caries it to any individual input. Hope some of this helps. I gotta run. |
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Post by sumgai on Sept 13, 2020 12:09:11 GMT -5
I haven't chimed in for various reasons, but that's now going to change. First.... Hi, Ace!  How's tricks? Second.... Speaking of 'pedantic', I'm not gonna go down that road (BIMO, ash did a nice job in his asterisk note). Instead, I'm going to challenge everyone here to read up on, and come to an understanding of, two properties of active electronic components: 'slew rate', and 'ringing'. Get those concepts down, and you're well on your way to understanding why certain components are more pleasing to the ear (at least of a guitarist). Go. Study. Report back only if you wish. HTH sumgai |
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Post by ashcatlt on Sept 13, 2020 13:55:47 GMT -5
Yeah and some diodes actually look a lot more like some combination of resistor, diode, and capacitor. I stand by my statement though that threshold relative to signal, symmetry, and especially filtering on either side make a bigger, more easily controlled difference than just swapping out the clipping element.
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Post by JohnH on Sept 13, 2020 15:42:46 GMT -5
That KiCad has done a very nice job on drawing the circuit. Next is to run the Spice Sim. Can you call up a frequency sweep analysis and also a transient analysis (to see waveform shapes)?
If so id suggest plotting outputs after gain stage 1, and at the input and output of gain stage 2 and also at the final output. This will get you some insight into the tone shaping in each stage and then the clipping. try a small signal sweep from 100 to 10000hz, then sine inputs of different levels, starting very low, going up to about 1V. All that will generate a mass of plots, too much to see at once, but its a route map for a journey of exploration. As you gain insight, you can start probing the signal on the real box to listen to it at each point (feed it into a clean amp).
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Post by ashcatlt on Sept 13, 2020 15:57:47 GMT -5
Oh heck! I was going to suggest earlier that you make yourself an audio probe and poke around in the actual pedal to see what it sounds like at different points in the circuit. An audio probe is basically half of a guitar cable with a largish capacitor soldered to the inner wire. Alligator clips can make it easier to attach. Plug the end you didn’t cut off into an amplifier or something so you can hear, hook the shield to a convenient ground point inside your pedal, and just poke around with the capacitor while you run some signal through it. The cap blocks DC so you don’t have to worry about damaging your amp or messing up the bias in the pedal.
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Post by asmith on Oct 12, 2020 13:09:35 GMT -5
First.... Hi, Ace! How's tricks? Hi 'gai! Silly sumgai, tricks are for kids! I hope you're well. I'll gladly study. Got a direction to follow for "ringing?" It's a vague title to go on. Slew rate is easy enough. Once I report back having studied both, I'd like your own insight on active electronics' varying slew rates and ringing, and their effect on "tooob tooone" That KiCad has done a very nice job on drawing the circuit. Next is to run the Spice Sim. Can you call up a frequency sweep analysis and also a transient analysis (to see waveform shapes)? If so id suggest plotting outputs after gain stage 1, and at the input and output of gain stage 2 and also at the final output. This will get you some insight into the tone shaping in each stage and then the clipping. try a small signal sweep from 100 to 10000hz, then sine inputs of different levels, starting very low, going up to about 1V. All that will generate a mass of plots, too much to see at once, but its a route map for a journey of exploration. As you gain insight, you can start probing the signal on the real box to listen to it at each point (feed it into a clean amp). I'm struggling to get the Spice Sim working on my Linux machine, hence radio silence thus far. Sometimes this operating system remains a little too hobbyist. Just so you know. Thank you very much for your continued assistance. Oh heck! I was going to suggest earlier that you make yourself an audio probe and poke around in the actual pedal to see what it sounds like at different points in the circuit. An audio probe is basically half of a guitar cable with a largish capacitor soldered to the inner wire. Alligator clips can make it easier to attach. Plug the end you didn’t cut off into an amplifier or something so you can hear, hook the shield to a convenient ground point inside your pedal, and just poke around with the capacitor while you run some signal through it. The cap blocks DC so you don’t have to worry about damaging your amp or messing up the bias in the pedal. I'll do this as soon as I get my amp working!  |
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That could be cool, but maybe not what you want. It really would want another buffer to isolate the split point from the output. And mixing resistors of course.
How's tricks? 