1uF Capacitors

[Phend]

Hello:
Question:

In "general" (no schematic) are these 1uF capacitors interchangeable ?

a) Ceramic (small yellow, not ideal for the "signal path" ?)
b) Electrolytic (polarized, + / -)
c) Electrolytic (non polarized, BP or NP)
d) Film (quite large)
e) other ?

[GibsonGM]

Polarized electro's aren't intended for use in the signal path...being polarized, and facing an alternating current. They are supposed to exhibit distortion, degradation, other 'poor qualities'. I've sure done it, to no ill effect, but NP is best for values you can't find in poly etc.  I try not to use electros outside of power supplies at all, but sometimes you do need 1u, 2.2u etc.   Film can be hard to find in higher values like that.

Ceramic are said to be 'poo', best kept for filtering high frequencies so their value is small (10-560pF). I only use them in tone stacks or as bypass caps on opamps or whatever.

Film...mylar, poly...all interchangeable. The only ones in your list I'd say no to if in signal path is polarized electros and big values of ceramic.  Just based on experience and 'common wisdom' from reading others discuss this.

[mozz]

Ceramic disks can also be microphonic.

[merlinb]

In a guitar pedal they are interchangeable, with the caveat that polarized caps might not be suitable for certain positions in circuit. Capacitor distortion is irrelevant in a guitar pedal.

[Phend]

Here is an example, see 1uF at 1 , 7 and 14 for instance..

[Kevin Mitchell]

In general, yes they are interchangeable.
My old rule of thumb was; if it's in the signal path, it can be whatever - polarity irrelevant. But if it goes to ground, polarized electro is a safe bet.

If space is a problem, the traits of ceramic C0G is comparable to film.
Most of the bad mojo about ceramic caps are regarding the old disk type. Nowadays, X7R is prevalent and really not so bad.

[GibsonGM]

Here is an example, see 1uF at 1 , 7 and 14 for instance..

In my life, to be honest, anything 1u and up would be polarized electros, because that's what I have on hand and...just because   I have probably 50 each of 1, 2.2, 4.7, 10, 22, 47 and 100u electros that I bought some time back because they are cheap, and readily available.  Not once have I ever had one fry, sizzle, burn or distort that I can tell.    Anything < 1u, is a poly film. Because I bought like 5 of those 'cap kits', so I have millions of them, ha ha.

The ones in the Rebot signal path show polarized, so they must not be worried!

Mozz: By "poo", yes, I meant grainy and microphonic. 

[mozz]

I have a old Premier tube amplifier, sort of a tweed deluxe, it has all disk capacitors. Didn't have to replace any except the electrolytics.  Doesn't sound bad at all.  I did have a homemade pedal and one of disk caps was really noisy, when you tapped on the board you couldn't pin point it, it was really bad but the circuit worked. 

[antonis]

if it's in the signal path, it can be whatever - polarity irrelevant.

   
Hmmm...

[GibsonGM]

I like to face the "+" toward where it's more "+"   

[Kevin Mitchell]

   
Hmmm...

Right in the pride 

I like to face the "+" toward where it's more "+"   

I feel like he did that just for me 

[antonis]

Electros can withstand 1V (or so) reverse potential difference, hence C6 above could indeed be placed either way around..
(but better safe than sorry..)
Positive plate facing towards T1 Emitter is one way for C2..

[GibsonGM]

I feel like he did that just for me 

Ah, we've all been there! From one New Englander to another, "You walked right into it, bub...."   

Got snow?  Time to plow, 6" on the ground here.

[FiveseveN]

Here is an example

So has anybody else noticed that those caps don't need to be that big (high in value)?

[antonis]

Probably they wish to have peace of mind..

e.g. 1μF output cap could be 50 times smaller for infinite load (-3dB at 80Hz) but marginally OK for 2k load..

[Ben N]

For 1uf, where space is an issue, you can sub MLCC or tant for film.

[BJF]

Hi there,

Some 17 years ago I answered in an interview for the Japanese Effector Book why I used Jamicon elkos considered consumer grade rather than the most expensive elkos at the time.

I do use elkos in signal path mainly because of the size of miniature elkos. In may ways the miniature elkos behave like tantals and therefore
They must not be reverse polarized or they can permanently  turn into something completely different than a capacitor such as a combined resistor and semiconductor junction, which actually can be really interesting in transistor circuits. Reverse polarization less than a few percent of Voltage rating the mini elkos can recover from while back in the 70s and 80s elkos could be reversed polarized up to 35%  of the DC voltage rating for reliable design. It was a consensus that tanks were just better and especially the metal cans.
1uF dip tantals were used in some 70s pedals eg MXR and copies and if we look at the time they were made and units working today they do have an impressive life span. I personally avoid using those because they are mechanically fragile.
Here in repair it is a good idea to check polarization in circuit because in some older electronics such often in commercial music electronics
elkos can by design be reverse polarised part time such as in oscillators where economics department saved on two components. Sometimes this capacitor hs a large voltage rating to ensure stability but not always.
Specifically on 1uF elkos those can be found in signal paths where they are exposed to reverse polarisation ( in many 70s designs) and it can then be a good idea to replace them with a non polarised capacitor.
An example can be budget and even mid priced  mixer consoles typically with dual supplies.
Back in the 1980s there was a lot of discussion in electronics magazines about distortion of electrolytic capacitors specifically in mixer consoles and other studio equipment while not really in effects pedals.
When replacing with modern parts it would be advisable to take two elkos twice the value and connect the minus sides together and connect a large resistor such as 1M to most negative supply point to ensure polarisation-the operative being polarization so plus sides can be connected and and resistor to most positive point can be used whatever is convenient. This practice is found in older high end products and then modern miniature elkos can directly replace older elkos because polarisation is guaranteed. 


Early sad ceramic capacitors  100nF and higher capacitance where subject to break down and they could randomly turn into low value resistor or a zener junction so they were banned a while from used in critical equipment nd in my personal experience I traced a breakdown in a 200W transistor power amp to an smd capacitor of 470nF decoupling a transistor in the differential stage- it is not the first thing you would expect in a havoced 200W CMOS output power amp.
 
 In my work I have seen minielekos perform in-40C in the Alps and 80% humidity in Florida and at 45C and even recovered from being  drenched by water as long as AC voltage does not reverse polarise life expectancy can be similar to tantals.
Older elkos can convert to noise generation and they can be easily spotted in repair with freezer spray as noise stops when the noisy part is freezed.

Yes disc ceramics especially larger values can become microphonic- a plain isolated wire with one end tied to ground can be wrapped around it at shield and mirophonics can be negliable.
Typically I use 500V Hitano ceramic discs and in values less than 1200pF, and they have shown excellent stability through decades but otherwise I avoid ceramic capacitors for low frequency signal chain maybe also because I would be a capacitor snob You know sometimes parts just look cool:)

So for 1uF capacitors in signal path it is advisable to part from building size to look at polarization.Miniature elkos can have some distortion but considerably less than older types and not necessarily in a bad way either.

There are plastic types of 1uF that do not build higher than an IC in a socket but they are hard to find and often listed at minimum quantity 1000 pieces and waiting time two months. But Wima makes a 50V version 1uF that is  couple of mm shorter than the 63V type that  I can recommend.
But as long as sufficient voltage polaraisation is observed in my humble opinion miniature elkos are just fine and the ever so slight contribution to sound they make in my designs desirable.
.

Have fun
Bjorn Juhl
BJF Electronics
Sweden


 

[Kevin Mitchell]

Got snow?  Time to plow, 6" on the ground here.

Never trust a woodchuck

[GibsonGM]

Never trust a woodchuck

      Mmm, just rolled up the yard with the plow truck...good times!  Mud season 3 next week.

[Phend]

Snowing hard here in VT, power goes out then on then out / on.
Trees are bent over with heavy snow.
I like to put 1000uF caps right up front so when the power does go out the effect still keeps going,
but the amp doesn't, hum.

We will be able to see some of the eclipse here on Monday, heard you might be able to see stars / planets.
Wonder if we will be able to see the moon too ?