Polarized vs. non-polarized output cap?

[Burstbucker]

What would be the advantage of replacing an electrolitic polarized output cap with a film cap of the same value?  Less noise?

I've read that Keeley prefers non-polarized caps.

[MartyMart]

Where possible ( smallish values ) I'll always use NP caps, WIMA,AVX etc
electro's in the signal path will add noise when there's a few of 'em !
Changing one or two, I simply cannot hear a difference, but its accumlative.
Marty.

[Burstbucker]

I'm talking about a 1uF cap, BTW.

[MartyMart]

I'm talking about a 1uF cap, BTW.

That's the largest value that I can find a useable size for, they're still quite big though ! 5mm square and 12mm high .... :shock:

Marty.

[wampcat1]

I'm talking about a 1uF cap, BTW.

That's the largest value that I can find a useable size for, they're still quite big though ! 5mm square and 12mm high .... :shock:

Marty.

Hey marty,
Have you tried the digikey Panasonic 1uf caps? They are very small in comparison.

Brian

[DavidS]

AVX has some that are 7.5x5mm, 8mm high. Mouser part number 581-BF074D0105J for $.44 in single quantity, 5% tolerance. Still kinda chunky...

[MartyMart]

I'm talking about a 1uF cap, BTW.

That's the largest value that I can find a useable size for, they're still quite big though ! 5mm square and 12mm high .... :shock:

Marty.

Hey marty,
Have you tried the digikey Panasonic 1uf caps? They are very small in comparison.

Brian

I'll check that out, here in the UK I found some "very small" 1uf's at
RS Components ( not radio shack!! ) they were 4mm square and 7mm
high ..... but were THREE DOLLARS EACH  !!!!!   :shock:
I've never found any 2.2uf's smaller than a "Bazooka joe" bubble gum !!

Marty.

[brett]

Hi.
Check out MKT poly caps.  I don't know what MKT stands for, but they come in standard sizes (about 3 sizes covers everything from 0.001uF to 2.2uF).  I'd always use a 1uF MKT in preference to an electro.
They are high quality, SELF-HEALING, don't crack, etc....
Electros not only have lower sound quality.  They have limited lives.  And I've heard that small electros hold such a small amount of liquid that they are even more prone to drying out.
cheers

[MartyMart]

Hi.
Check out MKT poly caps.  I don't know what MKT stands for, but they come in standard sizes (about 3 sizes covers everything from 0.001uF to 2.2uF).  I'd always use a 1uF MKT in preference to an electro.
They are high quality, SELF-HEALING, don't crack, etc....
Electros not only have lower sound quality.  They have limited lives.  And I've heard that small electros hold such a small amount of liquid that they are even more prone to drying out.
cheers

I've had some MKT and MKK caps, they're great but were V- expensive !
Had values from 10n to 470n in a reasonable size too.
Do you know a good cheap source ?? ( not hot chilli BTW !! )
Thanks Brett,

Marty.

[WildMountain]

I am curious about this polar vs non-polar difference too. I have had a couple of occasions now that a schematic asked for non-polar caps 1uF, but I don't have them laying around. This was in the AMZ mini booster and in the BSIAB.
With the mini booster Jack told me to use a 1uF electro, it wouldn't make a difference in sound and in the GGG layout for the BSIAB there were indications of polar 1 uF caps (whereas the bill of materials said NON-polar). It works fine with electro's but now I am confused.
Why would these schematics (designers) ask for such a (relatively) hard to find, large, and expensive cap if the cheaper electro's work just fine? Is there a difference in sound after all? Is it a noise reduction thing?

[R.G.]

Polar electrolytic caps are what you do when you can't practically do anything else. The performance of polar electrolytic caps is in general worse than an equal-capacitance nonpolar electrolytic cap, and worse yet than a non-polar, non-electrolytic (NE) cap. However, polar electro is smaller than NP electro and that is smaller than non-electro for the same capacitance - sometimes a LOT smaller.

Polar electros have higher leakage and higher dielectric absorption than NP and NE caps. They have higher tolerances and sound a bit funny right at their rolloff frequencies with any given R.

On the other hand, it's not in general possible to get a 100uF cap in anything other than electrolytic, and if you discount large polypropylene film motor starting capacitors, you can't get anything over about 2.2uF or 4.7uF. And it's not possible to get a 1uF as small as an electrolytic in any other technology.

Then there are the purely design problems. A polar electrolytic must be applied so that it -never- sees a reverse voltage. Do this and the capacitor more or less quickly dies. If the reverse current is quite low, it may die a slow, prolonged death. Notice that even if you have, say, 3V across a polar electro and you feed it 4V peak of AC signal, it's still reverse polarized on signal peaks. And this is enough to badly affect its life.

NP electros can be reverse biased or fed AC just fine, as the dual polarized construction makes them hold up to reverse voltages in either direction.

In terms of sound: read my descriptions of caps and preferences in the FAQ and my posts. The search function is our friend.

[Dave_B]

Here's some info on MKT and MKK caps (among others) if anyone is interested.
http://users.pandora.be/educypedia/electronics/capacitorstypes.htm

It doesn't look like MKK's were designed for audio, though I don't pretend to know what difference it makes.

[JHS]

Most japanese stompboxes use NP electrolytic caps, because they are very cheap. They use 1uF or bigger NP electrolytics to reduce the bassloss in those caps.

You can reduce it to 47-220nF if you use polycaps, 'cos they don't have that big bassloss and they have much better, natural highend response.

You can substitute any NP electrolytic if you reverswire two normal electrolytics with double value in series, but personally I prefer polycaps (AVX or WIMA MKT)

JHS

[WildMountain]

Thanks guys, that helps a lot. It seems that caps are still a little hard to grasp for me. I'm always wondering why is this cap here? What's its function? What material cap would sound best here?
R.G. you're right, the search function is our friend. I'll try to read some more about this. This is fascinating stuff.
I guess I'll just have to get some more NP (film) caps the next time I stock up.

[MartyMart]

Most japanese stompboxes use NP electrolytic caps, because they are very cheap. They use 1uF or bigger NP electrolytics to reduce the bassloss in those caps.

You can reduce it to 47-220nF if you use polycaps, 'cos they don't have that big bassloss and they have much better, natural highend response.

You can substitute any NP electrolytic if you reverswire two normal electrolytics with double value in series, but personally I prefer polycaps (AVX or WIMA MKT)

JHS

That's interesting, so when a 1uf NP is called for ( when replacing a 1uf electro)
You can safely use 220n - 330n - 470n poly's ?
That's great news if there's no "real" bass loss  
Thanks,
Marty.

[bioroids]

That's interesting, so when a 1uf NP is called for ( when replacing a 1uf electro)
You can safely use 220n - 330n - 470n poly's ?
That's great news if there's no "real" bass loss  

That's not allways the case. If you replace a 1uf with a 470nf (no matter the kind of cap) you are doubling the knee frequency of the hi pass filter.

If with the original 1uf cap you had a knee at 20hz, then with 470nf you have it at 40hz, and with 220nf you have it at 80hz!

It will depend on the input impedance of the next stage, really. If we are talking an input capacitor, then you know what the impedance is (normally for a guitar stompbox is high and you can get away with 100nf probably). But if its the output cap, you don't know what's the impedance of the next stage, and you have to cover that (unless you use the pedal under controled conditions i.e. you know where is gonna be connected).

What I'm saying is that you can't assume that replacing a 1uf with a 470nf or 220nf has no effect in bass response. May be the case, or may be not.

Luck!

Miguel

[petemoore]

Tacking a small poly or other cap across a larger electrolytic is supposed to help that position pass highs I heard...or think I read.