Stuff you wanted to know but were afraid to ask

I'm wading through some "noise-killing" threads, trying to compile an order of operations for minimizing unwanted garbage in fuzz pedals especially. A lot of (likely dumb) questions are popping up, but I have a quick polarity question - is it ok to use a non-polarized emitter cap, like a large-value (4u7 etc) MLCC? Looking at a Fuzz Face for example where it goes from the Fuzz knob to Ground, but I'm sure there are others. I realize you always need polarized caps in the power section, but I'm not sure here. Also - I assume when raising the Input cap into the uF range I can simply switch from box film to higher-value MLCC (since the highest box I have is 1uF).
 
Ginsly said:
I'm wading through some "noise-killing" threads, trying to compile an order of operations for minimizing unwanted garbage in fuzz pedals especially. A lot of (likely dumb) questions are popping up, but I have a quick polarity question - is it ok to use a non-polarized emitter cap, like a large-value (4u7 etc) MLCC? Looking at a Fuzz Face for example where it goes from the Fuzz knob to Ground, but I'm sure there are others. I realize you always need polarized caps in the power section, but I'm not sure here. Also - I assume when raising the Input cap into the uF range I can simply switch from box film to higher-value MLCC (since the highest box I have is 1uF).
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In general, you can use a non-polarized cap where the circuit calls for a polarized one--but there are often reasons not to, including size, cost and properties beyond capacitance (such as ESR, thermal stability, voltage ratings, etc.).

In a fuzz circuit I wouldn't worry much about mlcc vs film--I doubt you'd notice a big difference.
 
spi said:
In general, you can use a non-polarized cap where the circuit calls for a polarized one--but there are often reasons not to, including size, cost and properties beyond capacitance (such as ESR, thermal stability, voltage ratings, etc.).

In a fuzz circuit I wouldn't worry much about mlcc vs film--I doubt you'd notice a big difference.
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Gotcha, thanks! I'm wondering how to identify when not to swap polarized for something like mlcc.. For example, the Fuzz Face emitter cap I mentioned - seems like it'd be ok as a ceramic cap in this case..? If polarity isn't important in that position, maybe it's always been designated as an electrolytic cap more due to their ubiquity in the uF range? (This example is from a PNP Fuzz Face, thus positive going to ground):

Screen Shot 2025-01-10 at 2.30.16 PM.png
 
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Ginsly said:
Gotcha, thanks! I'm wondering how to identify when not to swap polarized for something like mlcc.. For example, the Fuzz Face emitter cap I mentioned - seems like it'd be ok as a ceramic cap in this case..? If polarity isn't important in that position, maybe it's always been designated as an electrolytic cap more due to their ubiquity in the uF range? (This example is from a PNP Fuzz Face, thus positive going to ground):

View attachment 88499
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combination answer ...
first one: there weren't 20uf ceramic caps available in 1960s Great Britain. ceramic caps in those values haven't been available to the general public until relatively recently

second one: just because a part comes in a particular construction (ceramic, film, electrolytic) or package (smd, through-hole, radial/axial) doesn't mean that it will be good for your given application. more information would be required like data sheets in order to tease that out and even then it may be non-obvious until you're 2 days into trying to figure out why it doesn't sound right
 
ICTRock said:
there weren't 20uf ceramic caps available in 1960s Great Britain. ceramic caps in those values haven't been available to the general public until relatively recently
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Had no idea! Well, guess that's why large cap values are typically electrolytic/polarized. Very good to know.

ICTRock said:
just because a part comes in a particular construction (ceramic, film, electrolytic) or package (smd, through-hole, radial/axial) doesn't mean that it will be good for your given application. more information would be required like data sheets in order to tease that out and even then it may be non-obvious until you're 2 days into trying to figure out why it doesn't sound right
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I'm still wondering about certain designations in schematics, and when a polarized cap really matters - still not sure if that 20uF Fuzz Face emitter cap can be changed to a non-polarized MLCC, for example. Can it? Why? I've seen posts by people who replace most of the polarized caps in circuits with non-polarized, and I'm not sure how to determine when that is ok to do and why people do it. I assume it has to do with the lifespan of electros, package size, or possible leakage considerations.
 
You don't have to use a polarized cap on that portion of the fuzz face circuit. An unpolarized cap like a polyster film capacitor or ceramic will allow the circuit to function. The thing is using a smaller valued capacitor there will change the sound. It's not about the construction in that case, but the value. They used an electrolytic because that was the best way to get a capacitor with that large of a value.

It's really easy to test this out on a breadboard if you're interested.
 
cdwillis said:
You don't have to use a polarized cap on that portion of the fuzz face circuit. An unpolarized cap like a polyster film capacitor or ceramic will allow the circuit to function. The thing is using a smaller valued capacitor there will change the sound. It's not about the construction in that case, but the value. They used an electrolytic because that was the best way to get a capacitor with that large of a value.

It's really easy to test this out on a breadboard if you're interested.
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Thank you - now I know it won't go up in smoke if I try it! Once in a while I like to clear something up before I start swapping components on a breadboard - I've already fried some things doing that, but learned a valuable lesson.
 
Ginsly said:
Had no idea! Well, guess that's why large cap values are typically electrolytic/polarized. Very good to know.


I'm still wondering about certain designations in schematics, and when a polarized cap really matters - still not sure if that 20uF Fuzz Face emitter cap can be changed to a non-polarized MLCC, for example. Can it? Why? I've seen posts by people who replace most of the polarized caps in circuits with non-polarized, and I'm not sure how to determine when that is ok to do and why people do it. I assume it has to do with the lifespan of electros, package size, or possible leakage considerations.
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You need a polarized cap if there's DC or potential for DC or different levels on each side of the cap.
 
Ginsly said:
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I'm still wondering about certain designations in schematics, and when a polarized cap really matters - still not sure if that 20uF Fuzz Face emitter cap can be changed to a non-polarized MLCC, for example. Can it? Why? I've seen posts by people who replace most of the polarized caps in circuits with non-polarized, and I'm not sure how to determine when that is ok to do and why people do it. I assume it has to do with the lifespan of electros, package size, or possible leakage considerations.
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It is fairly common to sub-out electrolytics from the signal path for box-film or for MLCC.
1) Box-film supposedly sound better — less noise I suppose.
2) Box-film will last longer than electros, which will eventually puke out their guts.

The biggest box-film caps I've got are 2µ2, great for bassifying builds.
I'm aiming to get some of the WIMA 4µ7 box-film, so circuits such as Rat etc can have all box-film in the audio-path.

Some people say they hate the sound of tantalum caps, others are proponents for their use — say in builds where big value electros are spec'd in the audio-path. I've got tantalum in my Rat-clone, as it's a 1590A build with mods and tants were the only size/value that would work.


Anyway, I liked your question about the emitter Fuzz-Face cap, had been wondering about that one myself, too.
 
Hey folks,

Got a couple projects that I'm wrapping up. 1: PPCB Electrovibe 2: is a project i'm just starting(bread-boarding currently) a clone of the BYOC Octave Fuzz, which I think is a clone off a Fulltone Octafuzz. For all three of these i've ran into a similar problem(schematics and images attached)

1 I'm all but done with my PPCB electrovibe. but C11 and C22 accidentally put caps rated at 16V in there. How important is the UF rating on things like this? Could I use a different value cap (uf value not voltage).

2 on the octave fuzz C4, kinda a similar question. How critical is that value. I am out of .001 caps. can I go with a .0047 or .01?

I know these are dumb questions, but any help would be cool! is there a formula to figure this out by myself? I know the best thing would be wait for my tayda order. and thats probably what i will do. But this is often a question i've wanted to ask. ppcbelecvibe_layout.png ppcbelecvibe_sch.png ppcbpost_byoc.png
 
C11 is going to get 18v, so 16v won't be enough. C22 is going to get 15v, but I still wouldn't stick a 16v cap there. I usually use 35v rated electrolytics in the power section even if I'm not planning on running higher than 9v, just in case I (or anyone) uses a 18v power supply on accident.

On the octave fuzz I'm guessing that the R6 and C4 are filtering out high frequency noise. Using a larger cap might make it sound like it's got a blanket over it. Someone else may have a better answer.

If it were me I would just order the correct components and wait to finish them as annoying as that may be. It's better than getting it done later and wondering if it sounds right.
 
on the octave fuzz r6 and c4 form a RC Filter ... so you can use a different cap if you compensate with a different resistor too otherwise you are going to be playing with the tonality of the pedal for good or bad

on the electrovibe, keep in mind that the values there provide filtering for the 18 and 15v supplies ... you don't want to go lower (noise potential) and I don't have a good handle on what the upper limit should be on going larger at 2AM on a Monday morning. you could probably get away with 220uf but I wouldn't be surprised that there be monsters I didn't consider
 
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ICTRock said:
on the octave fuzz r6 and c4 form a RC Filter ... so you can use a different cap if you compensate with a different resistor too otherwise you are going to be playing with the tonality of the pedal for good or bad

on the electrovibe, keep in mind that the values there provide filtering for the 18 and 15v supplies ... you don't want to go lower (noise potential) and I don't have a good handle on what the upper limit should be on going larger at 2AM on a Monday morning. you could probably get away with 220uf but I wouldn't be surprised that there be monsters I didn't consider
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okay thank you, what your saying makes perfect sense on the octave fuzz. i'm breadboarding it as i type this, so perfect time to screw around.
Yeah on the electrovibe I was kinda guessing that so i got 50 of them coming at 25v to backstock. thank you!
 
Let's say I have a JFET source follower where the drain is connected through a 100R resistor to a regulated 24VDC (+/-1%). Am I cutting it too close if I'm using FETs that are rated for 25V max drain-gate voltage, like 5457, J211, etc or are these rated rather conservatively?
 
You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?
 
UtilityBeltFX said:
You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?
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Do they use discrete transistors? If they got 4 of them fabricated on the same substrate they could get a very high rate of matched quads and they may also be easier to test if they are all on the same chip. That’s what I would do.
 
UtilityBeltFX said:
You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?
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I once had this very question and found the answer from Mark Hammer and others on diysb

lots of questions on fet matching for phasers

lots of questions on fet matching for phasers
www.diystompboxes.com
 
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