OT *battery box* caps

[bwanasonic]

Eventually I want to make a little preamp to use with my minidisc, but for now I will suffice with a *battery box*. Could someone tell me which way the caps would go in the following diagram if I use polarized? :

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              --------------||---------------------------hot--- (left)
              |           1 or 2.2 microfarad
from left mic  |           input capacitor
              |
---hot--------+----10k ohm-- "+"
                              \
---ground----------------------)---+--------------------shield-----
                              /    |
---hot--------+----10k ohm-- "+"  "-"
              |    resistor   9 volt
from right mic|               battery
              |
              --------------||---------------------------hot--- (right)
                          1 microfarad
                          input capacitor

I might end up using  1uf film, but if I end up using electrolytics I want to know which way to orient them. Also any way to match caps if I don't have a meter that does capacitance?

Thanks
Kerry M

[spongebob]

There's a better schematic and a bass rolloff calculator on this page:
http://burak.relyon.ca/live/battbox.html

[Peter Snowberg]

The + side will face the battery, but I would advise the use of film caps for better sound.

For matching without a meter.... you could try building am oscillator with a 555 and substituting the cap with the one under test, but that won't give you much to worth with unless you also have a frequency counter. :? I would just use good caps with a lower tolerance (read as avoid electrolytics) and call it a day. They're for DC blocking and should be passing ALL the audio with room to spare anyway. It's not like an amplifier driver stage where they're also actively filtering the sound.

Take care,
-Peter