• Angela

Why not give us a specific example of an amp you are trying to recap? I'm sure we can give you a better idea of possible part selections.

Remember that most electrolytics are -30%/+70% at best. There is really no difference between a 40uf and 47uf cap. Also voltage ratings are minimum - it's fine to go higher.

If you find yourself recapping vintage gear often, consider getting one of the older cap checkers. My favorite is the Heathkit IT-11/IT-28, but the Eico 950B or Sprague's are also very nice. They let you measure leakage at up to 600vdc - and are perfect for reforming older electrolytic types.

- Gary

• http://www.the-planet.org

6DJ8 Tube Crossover

I put a few more components in the circuit model to provide horn compensation, but the Spice model is easy to modify for whatever crossover points and what-not. The OrCad schematic that the model uses is nice too. I don't know if you're interested, but if so, feel free to link it on your website.

For example, you have a 20uF and a 35uF cap in series.
1/20 = .05
1/35 = .02857
.05 + .02857 = .07857
1/.07857 = 12.7uF

The series capacitance will always be smaller than the lesser of the two caps' values. The voltage rating is exponentially increased as well. For series caps with the same voltage rating, I personally wouldn't exceed around 75% of the combined voltage rating in use.

If the series caps have the same capacitance, then dividing the common value of the caps by 2 is easier than using the formula. For example, two 20uF caps in series equals 10uF. If you have the room in the chassis for the big guys, Solen FastCaps have a 630V rating and performance wise will eat aluminum electrolytics for lunch.

Hope this is of some use to you.

Thermionic

Russellc