Capacitors: My FAQ

[Dolmetscher007]

I am doing a lot of reading, and I've done a fair amount of internet research as I begin learning about the basics of electronics. There is a lot to learn in general, but some of the more difficult things to find clean and clear information on are the components themselves. I have to start somewhere, so Capacitors it is.

Here are all the questions that I am having as I get started with sourcing and placing my first electrical components order.

• Point-to-point construction vs. PCB:
  Not necessarily a capacitor-specific question, but since capacitors vary so much in size, this question came to mind. With tube amps, it seems like the phrases "hand-wired" and "point-to-point" are a big deal. The letters PCB feel kinda shameful for some reason on forums. However, in the pedal game, PCB seems to be pretty much the only thing I've ever seen. Pedal size, shape, and design not being an issue, and you wanted to build a simple distortion pedal that was the size of a VCR... i.e. you have all the room in the world, would one still use a PCB for a pedal? If so... why? If not, why not?
  


• Spacing:
  On a Build of Materials (BOM) of a pedal PCB-only kit that I just built, it says: ––  .0039uF  ––  5mm spacing  ––  Ceramic / Film / Box  –– Since this is a through-hole PCB, I know that there are holes for the leads to fit into. When a BOM or schematic says "5mm" under "Spacing" I imagine it means that the "Lead Spacing" on the component needs to match that distance.
  My question is... if you find a component that is 7.50mm for a 5mm PCB slot... or a 3.50mm for a 5mm slot... can you not just bend the leads a little to make it work? Is that considered sloppy, and would get your pedals laughed at by other pedal-heads? Or is it genuinely a bad practice and has a real reason as to why that should not be done? Or is it totally fine, who cares?
  


• Applications:
  I see things like: Automotive, General purpose, EMI, High Frequency, Switching; High Pulse, DV/DT, RFI Suppression... In my mind, for guitar pedals, none of this really matters. There's no reason to avoid caps labels as being for "Automotive" just because it says that. Correct? Or are there some "application specific" caps that are to be avoided?
  


• pico, micro, nano, Farads:
  I know that there are online calculators for these things, and I know that it is just moving the decimals to easily see that 0.0039 microFarads is absolutely equal to 3,900 picoFarads. But if the designer of the pedal lists the part as 0.0039uF is there any reason, whatsoever, to seek out one that is labeled by the manufacturer in uF, or can you just buy one that is labeled as: 0.0039uF, 3,900pF, or 3.9nF, and they all are the exact same?
  


• Ceramic, Film, Mica, Silicon:
  There is a TON written about this on the internet, so I know most of what is said, but I also know that the pedal forums basically seem to say... screw it! Pedals have always been made with cheap parts, and that if there is an electronics part, and you can buy it... it's good enough. Don't be a parts material snob. I am absolutely A-okay with that idea. Is there anything that someone might have to say that IS considered a pretty universally accepted No-No for guitar pedals and capacitor materials.
  

I have more questions, but I think that the answers to these will likely answer my other questions. I really appreciate and thank you all who respond in advance for your help!

[EBK]

I'll tackle the easiest question first.

4.  Where the values are equivalent, it doesn't matter at all whether the manufacturer chose to label the part in nF, uF, or pF. 

1 and 2.  No one here will make fun of how you build your circuit.  If anything, we have high regard for creativity.  If anything is "sloppy", we will happily help you improve.  We aren't competing against each other.  PCB and non-PCB builds are equally fine.  Again, if you point-to-point build something everyone else is using a PCB for, you will likely receive praise rather than negative criticism.  Bending leads on smaller or larger parts to make them fit is fine as long as you aren't shorting something else out on the bent leads (i.e., as long as it works, it is good).

[highwater]

1: RG's website has a nice page comparing various construction techniques.

2: Bending leads is *usually* fine. It may offend your personal aesthetic sense. If you need to bend the leads on an IC you're going to have a bad day. Some diodes can be damaged if you bend too close to the body. You might need to add insulation, for instance if you bend the leads on a transistor around to fit a different pinout. Generally, though, it just needs to fit in the box and not short-out.

3: All that really matters is that the specifications meet your needs... but stated application can be handy to quickly rule-out parts without looking at the datasheet. For instance, a low-voltage rail-to-rail opamp designated for "instrumentation" is likely to be too slow for audio (but might be perfect for an expression-pedal). A resistor designed to be used as ballast in an automotive ignition system is going to be way bigger and more expensive than you need for a stompbox, but will work fine if it's all you can get in that value (and might be perfect for a tube amp). Occasionally things can be too *good*... a video opamp might be more prone to high-frequency oscillation than one that's only fast-enough for audio... but even then you can probably still make it work.

4: As EBK said, it doesn't matter a lick what units it's labelled in. Just make sure you don't get confused about which is which; if all the caps in your parts drawer are labelled in the same manner it's a lot easier to pick-out the one you want.

5: Some people swear they can hear a difference, but as long as you don't stick a polarized cap somewhere you shouldn't have you can use whatever you have/can get/want. You can use a film cap *anywhere* that the circuit specifies an electrolytic (if it's not too big or too expensive), but there are places where an electrolytic won't work. Most builders try to avoid using ceramics in the signal path, but it's not absolutely necessary... and some types of ceramic are worse than others (I always have to look-up which types are the "good ones").

[ljudsystem]

1. Point to point or tagboard isn't that common I think unless you build small effects like fuzzes or boosters. The two big ones for stompboxes are vero board (or strip board) and pcbs.

Since veroboard is cheaper and I've wondered what the benefits of using pcbs are since some people prefer them. The obvious is that pcbs can be made a lot smaller so you can cram more into smaller enclosures. Theoretically a well designed pcb should minimise noise as well though I don't know if that will be noticable in most guitar pedals.

What I've found now that I build bigger and more complex pedals is that I almost allways mess something up when working with veroboard. It's Very easy to forget a link, or wire a componet wrong. PCB are much more forgiving in that sense.

[GibsonGM]

Don't forget "perfboard".  I build everything on that, create my own layouts (tho not with any high degree of thought more than some basic rules).   I find it very flexible...no need for something as 'all done' as a vero layout, no need to etch.  I keep a bunch of boards lying around, can cut off what I need when I need it, no waiting...I can't be the only one who uses perf...

If I weren't so lazy, I'd probably go ahead and etch PCBs for my projects; that would make them neater. But perf works for me! 

[Prehistoricman]

4.
Pet peeve time! I hate it when values are written down in a way that doesn't make sense with the unit chosen. Go shopping for power banks and this is immediately obvious (20000mAh instead of 20Ah). I have some understanding with capacitor values as it's unusual to see millifarads and nanofarads were never used in the old days.

5.
Anything is fine really but ceramics often have large tolerances that could make your pedal/amp sound different as temperature, pressure, and age change. Multi-layer ceramics (usually SMD) have voltage-dependent capacitance! Use ceramics when the value doesn't matter a lot.

[PRR]

> tube amps, it seems like the phrases "hand-wired" and "point-to-point" are a big deal. ...However, in the pedal game, PCB seems to be pretty much the only thing

Tubes were originally wired on wooden boards, then "ebonite", then metal chassis with terminal strips or tagboards. While radios and TVs switched to PCB when expedient, the "good" guitar-amp makers (mostly Fender) persisted with tagboard for a very long time, because you can't rip pads off tagboards while repairing (i.e. ready maintainability or modification was considered valuable, unlike radio/TV products).

Transistor and their parts as used in pedals "last forever"; also a pedal is more a throw-away than an amp. Early pedals were done on lugs, but after the first batch of 100 the makers tended to look for faster (cheaper) way to assemble. Brooklyn was full of small shops making PCBs or/and contracting assembly work.

It's just a either-way cusp between history, tradition, and local facilities. Not "tone".

[thermionix]

...I can't be the only one who uses perf...

I use perf mostly, and get PCBs from Madbean and GGG for some more complicated circuits, especially things with LFOs that can have noise problems if not laid out well.  I think I've only used vero twice, and one of those is no longer in an enclosure.  For my first few builds I made eyelet boards, because I already had the stuff.  Still in my wah.  If I did that now though, it would be on perf.

[Dolmetscher007]

Here's my quick recap to update where I am with these questions...

1.) Point-to-point construction vs. PCB:  Point to point makes no sense in the pedal world. There is nothing wrong with PCBs in guitar pedals.

2.) Spacing: It is fine to persuade (i.e. bend) the leads of components as long as it is within reason (no 19mm parts bent into a 5mm slot), and as long as it doesn't touch or short out some other part of the circuit.

3.) Applications: As long as the values, the tolerance, the spacing, and the material is right, it does not matter what a vendor lists as it's recommended/intended application.

4.) pico, micro, nano, Farads: As long as the value is accurate, it doesn't matter which unit they use to label it.

5.) Ceramic, Film, Mica, Silicon:
pF - Ceramic or Film
nF - Box/Film
uF - Electrolytic

I think I've "got it" enough to move on to resisters.

One non-cap question though...

• Perfboard
• Tagboard
• Veroboard
• Stripboard
• Breadboard

Some of these sound like brand names, but some sound like generic items. Breadboards are plastic boards that have a grid system of holes on them that let you temporarily shove component leads into holes to quickly see if a circuit idea works in the real world, and so that you can run tests.

Other than that... I do not know what the other items in the list above are. It did occur to me after I asked question 1 above, that I do not know how on Earth anyone would point-to-point wire an effects pedal anyway. My confusions came from... if you do not have a printed circuit board made up, nor the ability or budget to make one or get one made... what options do you have? I imagine that one of the above items is that option. Yeah?

[amptramp]

1. I'm a big fan of prototyping boards.



The only place I would avoid PCB's is tube circuitry where the heat can burn the phenolic of epoxy-glass substrate.  The board shown above is good for DIP IC's and provides power and ground lines as well a connector area.  They are available in different numbers of pads that connect to the IC and you have holes for power decoupling capacitors.

2. Spacing: It is actually preferable to have bends in the leads for strain relief but not necessary.

3. Applications are not all that important.

4. Use whatever expression you like.

5. Avoid ceramic caps in audio - we already have another thread where changing a tone capacitor from ceramic to a film cap cured a microphonic oscillation because a ceramic cap is not that different from a ceramic microphone.

[PRR]

> Avoid ceramic caps in audio -

Below 1,000pFd, ceramic is unobjectionable.

Above 1,000pFd ceramics are made of different, less-perfect stuff. At 10,000pFd my ears can sometimes hear the effect; and as you say there may be non-audible problems too.

[Dolmetscher007]

Last caps question... for now. ;-)

In the BOM for this first pedal I'm building... it has the following caps listed.

1x -- 0.0039µF
1x -- 0.012µF
8x -- 0.1µF
3x -- 470pF
1x -- 22 - 47µF / 25V or more

I understand all of these, but the last one. It looks like it could be any cap, with any capacitance between 22µF and 47µF, and Voltage rated could be anywhere from 25V up to 500+ Volts. And just looking at the PCB and the example picture, the lead spacing is very small, 2-2.5mm. I looked on DigiKey, and Film Capacitors did not seem to work, so I went to "Aluminum Electrolytic". These are the tiny little "Barbie beer can" sized/shaped caps. 

So, i'm did find a few... but... I am not at all sure about the 22-47µF, or the 25V "or more" (). And the last thing I noticed is... all my other caps have a +/-5% tolerance. All of these aluminum electrolytic caps have +/- 20% tolerance. I don't know if that is too high, or what.

[highwater]

The schematic would be helpful to answer that.

Sounds like it may be for power filtering, in which case the exact value is irrelevant. 22uF was likely deemed "enough", and 47uF "maybe better maybe no difference".

25v... anything rated higher than that would be more expensive and physically larger but not detrimental to operation. 16v would be OK on 9v (unless there's a charge pump involved), but it's still a good idea to go for the 25v ones unless they absolutely won't fit.

As for tolerance, +/-20% is fairly common for electrolytic caps (another reason they're generally avoided when a film cap would be cheap/small enough).

[Dolmetscher007]

The schematic would be helpful to answer that.

Sounds like it may be for power filtering, in which case the exact value is irrelevant. 22uF was likely deemed "enough", and 47uF "maybe better maybe no difference".

25v... anything rated higher than that would be more expensive and physically larger but not detrimental to operation. 16v would be OK on 9v (unless there's a charge pump involved), but it's still a good idea to go for the 25v ones unless they absolutely won't fit.

As for tolerance, +/-20% is fairly common for electrolytic caps (another reason they're generally avoided when a film cap would be cheap/small enough).

Here's the schematic: http://permanentelectronics.com/DIY/P.E.CSSTB.rev1/P.E._Colorsound.Supa.rev1.pdf
Here's the Build of Materials: http://permanentelectronics.com/DIY/P.E.CSSTB.rev1/P.E._Colorsound.Supa.rev1.BOM.pdf
Here is a picture of the PCB w/ and w/o components on-board: http://permanentelectronics.com/

I can tell by the PCB holes that this has to be a pretty small cap. I just am not sure what else I might be missing.

[ljudsystem]

I must confess, I've never built anything on perfboard 

It just looks so messy on the solder side...

[bluebunny]

I must confess, I've never built anything on perfboard 

It just looks so messy on the solder side...

Do a search for some of Rick's (frequencycentral) perf marvels!  To call them "messy" would be a dis-service.

[ljudsystem]

Ok, yeah. That looks really neat. guess I should get over my fear and try some perfboard layouts.

[duck_arse]

One non-cap question though...

Perfboard
Tagboard
Veroboard
Stripboard
Breadboard

if you have a pcb for "a circuit", you build "that circuit" on that board. if you have a chunk of veroboard, or perfboard [or a breadboard], it's like a baseplate for lego - use your stock parts to build what the hell you like. the pcb has the circuit sorted and laid down for you, with perf you poke the parts thru the holes flat on the board for mechanical stability [.... why hole spacings matter ....] and then point-to-point connect them electrically underneath.

with vero [Vero is an english company that makes veroboard products], you get east-west strips of copper under, so you make cuts here to isolate parts from other parts, and then add jumpers north-south and fly-wires all over everywhere to make non-straight line connections. tagboards are just blank boards with lugs on, connect them as you like, big parts especially.

and a breadboard is the way to test a thousand different circuits each week, without wasting components on dud builds. also a way to never get anything finished to the boxing stage, but that's a different faq.

[EBK]

It did occur to me after I asked question 1 above, that I do not know how on Earth anyone would point-to-point wire an effects pedal anyway. My confusions came from... if you do not have a printed circuit board made up, nor the ability or budget to make one or get one made... what options do you have? I imagine that one of the above items is that option. Yeah?

Where there is imagination, there are always options. 



This project is almost two years old now.    I'm going to send the enclosure to my brother for painting (painting this has been much harder than soldering the circuit) so I can pick it up again and hopefully finish it.

[duck_arse]

This project is almost two years old now.   

pffftttTT! millenials.