BO-pre - Balanced output preamp.

Preamp based on Sowter transformers and triode strapped EL84.

All measurements done with 1200 ohm load:

   - Frequency range: 10Hz to 110kHz (+0/-1dB)

   - THD: 0.25% (1Vrms), 1% (10Vrms) (2nd harmonic dominant)

   - S/N: 80dB (ref 1V)

   - Output impedance: 165 ohm

   - Max gain 3.8x/11.5dB

   - Max output signal before clipping: 20Vrms.

The output transformers perform excellent, and the semi separate power supply/amplifier chassis seems to pay off regarding noise/hum.

An internal look into the amplifier section:

I will be using this preamp as a front end for some class D solid-state mono blocks (B&O ICE-power).

Jan E Veiset

Norway

15-JUN-2007

Valhalla[at]mikke-mus.com