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# Electronic Crossover

The original design is from L.E. Larsen and has been published in L'Audiophile.

It's a Sallen Key type.

The basic formula for such a filter:

for a second order filter
(12dB)

for a fourth order filter
(24dB)

This is true for OP amps because they have a gain at 1, an infinite input impedance and
an extremely low output impedance, but a tube cathode follower is not that close to an OP
amp:

- The gain is not one, but more often 0.8-0.9
- The input impedance is lower
- The output impedance is much higher

As the formulas and explanations given in the article were particularly obscure, I
don't give them here ...

## Crossover 7KHz, 12dB

This schematic gives a 7KHz crossover frequency and slopes with a 12dB attenuation.

## Crossover 5KHz, 24dB

This schematic gives a 5KHz crossover frequency and slopes with a 24dB attenuation.

## Power Supply

This power supply is identical for both schematics.