Tantalum caps

[Ears]

I've been considering using these as coupling caps in some solid state environments rather than electrolytics.

i) I understand tantalums are intolerant of being used with incorrect polarity but wonder if they actually require a DC bias to operate properly?

ii) In some environments it can be unclear as to the DC levels, if for example you are coupling two Op amps (but want to avoid amplifying any DC offset) or coupling the input to first stage op amp. I note that often electrolytics used in this manner have the +ve lead connected toward the op amp, irrespective of it being the input or at ouput terminal (see attachment as random example). Is there a general rule as how to orient them?


thanks

[LOUDthud]

There are tantalums that can be operated with reverse bias. You'll have to look at the real data sheet of the parts. Look on some websites that have links to the manufacture's data sheets. I forget if it's wet or dry types that can stand reverse bias. The attached schematic operates with a +6V virtual ground so + goes to most inputs and outputs. When there is no bias, often times polarity is established by the polarity of the opamp's input transistors. The bias is only millivolts. Most commercial gear uses aluminum electrolytics and they can withstand small amounts of reverse bias.

[Aurora]

Tantalums are usually concidered bad for audio no matter how you put it.
Reverse voltage is a definate no-no, and reverse DC usually makes them short out. I don't proclaim to know-it-all, but I've yet to find one that is reverse tolerant. Their only advantage is size vs. efficiency, in circuits where this can be used to advantage. So, simple conclusion, - why use it at all for audio circuits, be it guitar of HiFi.........

[Dai H.]

Neve!

[Ears]

Thanks for the replies Mr Thud and Mr Lights in the Sky, I conclude that sorting out required polarity polarity at op amp terminals is too complicated for me to figure out, to illustrate K O'Connor specs the exact opposite polarity for biploar caps (in TUT1) to Elliot Sound (http://sound.westhost.com/index2.html) for essentially the exact same reverb drive/recovery ccts, so who am I to decide .
I think I'll give tants a miss, although I've read a range of opinion elsewhere as to their transparency in audio ccts, I tend to suspect they'tre fine in places where there is a clear voltage bias.