H&K Red Box - Component Ratings?

[mremic01]

I came across this and thought it would be worth throwing one together: http://rapidriotboxes.blogspot.com/2009/02/di-boxh-red-box-mark-ii.html

What worries me is that I don't see anything about the rating for the components. Would the typical 1/4 watt resistors and caps rated for more than 9v work for something that's connected to the speaker output on an amp?

[Mike Burgundy]

Its a speakersim and DI, not a load box, so it doesn't take the power - the speaker still does. The rest is Ohm's law.
An reasonable approximation is a parallel circuit of the speaker (say 16 Ohms) on one leg, and the redbox' R2+R3 on the other.
From that you can calculate how much voltage the circuit sees (the R2-R3 junction is what to look for), and how much current goes through R2 and 3. Apply a safetyfactor and go.

Edit: By the way, I've just seen the new version - it's *tiny*! Always cool when distributors stop by to show new gadgets.

[PRR]

> 1/4 watt ...9v work for something that's connected to the speaker output on an amp?

The first thing off the speaker connection is a 470K.

Assume everything else is much less, so the 470K gets the brunt.

Assume you use 1/4W.

The Voltage for 1/4 Watt of power in 470,000 ohms is square_root(470,000/4), or 323 Volts.

There's no speaker line with 300 Volts on it. 30V is more like it. (28V in 8 ohms is 100 Watts.)

Or forgetting Ohms Law and Power and square-roots: if a 4 ohm speaker and a 400,000 ohm resistor get the same voltage, the resistor takes 4/400,000th of the power the speaker takes. Pencil a monster 1,000 Watt in 4 ohm amplifier, the 400,000 resistor takes 1,000Watts/100,000 or 0.01W or 1/100W.