Electrolytic vs Tantalum

[Gus]

This is a link to some of the best PDFs about caps on the web.

http://main.diycore.com/index.php?categories=Passive%20Components

[Bill Mountain]

I was looking at some old solid state amp schematics (Sunn Coliseum 300) and I see stuff like 10/NP a lot.  I assume this means 10uf non-polarized.  I also assume this means tantalum caps.  Can anyone surmise why in an amp that has plenty of room for larger electrolytics the designers would choose not too use them?  These caps are in the signal path as well.

[artifus]

$

[Bill Mountain]

$

I was assuming tantalums were more expensive.

[artifus]

depends what you've got in stock, bulk deals special offers, etc.

was a bit of a flippant post, sorry. just a cynical guess. s'pose the way to tell would be to compare two versions of the same model manufactured at different times.

[Seven64]

So what I am getting from this thread is that they are great and they sound like $h!t   

[DavenPaget]

Tants ... They tend to blow up easily 

[PRR]

> solid state amp schematics (Sunn Coliseum 300) and I see stuff like 10/NP a lot.

What power supplies?

Bipolar (+/-) supplies allow opamp outputs and inputs to sit at zero volts DC. However it's never exactly zero; also we don't want DC flowing through. So there's blocking caps. The "zero DC" could be off a fraction of a volt in either direction + or -. So a non-polar cap is needed. The resistances are often low, under 10K, so a large cap is needed, bigger than a practical film-cap. Anyway 10uFd electro is cheaper than 1uFd film ("$"). So they spray 10uFd non-polar electrolytics.

These will normally be aluminum, not tant.

[Bill Mountain]

> solid state amp schematics (Sunn Coliseum 300) and I see stuff like 10/NP a lot.

What power supplies?

Bipolar (+/-) supplies allow opamp outputs and inputs to sit at zero volts DC. However it's never exactly zero; also we don't want DC flowing through. So there's blocking caps. The "zero DC" could be off a fraction of a volt in either direction + or -. So a non-polar cap is needed. The resistances are often low, under 10K, so a large cap is needed, bigger than a practical film-cap. Anyway 10uFd electro is cheaper than 1uFd film ("$"). So they spray 10uFd non-polar electrolytics.

These will normally be aluminum, not tant.

Thanks.  Learn something knew everyday!

[diagrammatiks]

I was looking at some old solid state amp schematics (Sunn Coliseum 300) and I see stuff like 10/NP a lot.  I assume this means 10uf non-polarized.  I also assume this means tantalum caps.  Can anyone surmise why in an amp that has plenty of room for larger electrolytics the designers would choose not too use them?  These caps are in the signal path as well.

non-polarized can be electrolytics as well.

since they are in the signal path they should ideally be non-polarized.

[PRR]

> non-polarized can be electrolytics as well.

Both Aluminum and Tantalum are "electroltic".

In causual conversation, "electrolytic" usually means Al; if there is some reason to pay much more for Tantalum, we get specific.

> since they are in the signal path they should ideally be non-polarized.

Signal caps with any significant and reliable-polarity DC across them, such as coupling caps in uni-polar supply applications, can (and usualy should) be simple "polarized" caps, not the more complex and expensive non-polar type. Even with huge AC/Audio voltages, the voltage across the cap does not reverse.

I've also found non-polar caps to be less reliable, but that may just be bad luck.

[brett]

Hi
Let me be really clear. I don't care about non-linearity and microphonics in caps not carrying my signal. Non-signal caps should be big in uF, small in size, cheap and reliable.
In particular, the small size of those multi-layer ceramics make them perfect for decoupling the PS near op-amps. As we all know, proximal de-coupling of every op-amp is good practice.
A cheap, tiny, dry, non-polar, 1uF (ie multi-layer ceramic) cap is more-or-less perfect.
cheers