Aentons
Well-known member
Yep, this. Some people don't care about imposition.
Btw, could you come to my house and give me a foot massage. Thaaaaanksssss....
Stuff you wanted to know but were afraid to ask
- Thread starter spi
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Btw, could you come to my house and give me a foot massage. Thaaaaanksssss....
Brett
Well-known member
I used to get this when I owned a business. Did this once, don’t think they ever asked again:
Or when you're debugging a build with one...
F**k! Ahh! Crap!
>-/-8-O
CheapSuitG
Well-known member
The Stussy S! That is going on one of my next builds!
rwl
Well-known member
How should I read symbols on a schematic, where no pin is specified, the symbol appears symmetrical, but directionality is important for pins? In particular, I'm wondering about pots and JFETs. Here's some example pots to show what I mean:
PPCB schematics, and other more recent ones I've seen, will specify the pins pretty clearly. In the first case I'm pretty sure it's pin 3 at the top and 1 at the bottom, since that seems standard for volume. But I'm wondering more generally.
And here's the JFET:
My understanding is that for JFETs the drain and the source can mostly be used interchangeably, so I suppose from a schematic perspective there's no difference. But for transistors where pin 1 is drain and pin 2 is source, you can't easily convert the schematic to a PCB without some pin wrangling.
Am I missing something?
PPCB schematics, and other more recent ones I've seen, will specify the pins pretty clearly. In the first case I'm pretty sure it's pin 3 at the top and 1 at the bottom, since that seems standard for volume. But I'm wondering more generally.
And here's the JFET:
My understanding is that for JFETs the drain and the source can mostly be used interchangeably, so I suppose from a schematic perspective there's no difference. But for transistors where pin 1 is drain and pin 2 is source, you can't easily convert the schematic to a PCB without some pin wrangling.
Am I missing something?
cdwillis
Well-known member
I don't know that there is or was a standardized way of specifying which leg is which on a potentiometer on a schematic. If you know how the pot behaves either increasing or decreasing resistance you can figure it out (using legs 1 to 2 increases resistance, using lugs 2 to 3 decreases resistance). Legs get jumpered so that if the wiper fails the circuit can still function somewhat as if the pot is just a jumper on that portion of the circuit. On something like that speed control you'd have to know whether increasing speed would mean increasing the pots resistance or not.
Ginsly
Well-known member
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).
spi
Well-known member
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.
Ginsly
Well-known member
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):
ICTRock
Well-known member
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
Ginsly
Well-known member
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.
cdwillis
Well-known member
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.
It's really easy to test this out on a breadboard if you're interested.
Ginsly
Well-known member
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.
You need a polarized cap if there's DC or potential for DC or different levels on each side of the cap.
Bricksnbeatles
Member known well
Wait… have I just never noticed a notes section on PPCB checkout? I have drawings from mammoth (rip) and LMS, but I’m gonna need to add a Robert original I think
Nostradoomus
Well-known member
If the Canadian dollar wasn’t so bad I’d order something just for that. (I’ve got a doozy of a doodle)
Feral Feline
Well-known member
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.
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