Michalík BP-4

Active electronics - complete kit for easy installation into your instrument.

Active electronics BP-4 was designed in 2002 for the American bass manufacturer SPECTOR. Since 2003 it has been used in all European and some American models of this brand under the trade name TonePump. During this time, several top Czech bassists, including Jiří Veselý and Richard Scheufler, have had it installed in their instruments.

The main advantage of the circuit used is that it does not use operational amplifiers, like the vast majority of world manufacturers, but a special circuit with a JFET transistor, which behaves very similarly to a tube. Manufacturers using operational amplifiers often get around this problem by using two 9V batteries for power. But this only delays the problem and does not solve it. In addition, other devices in the signal path - amplifier, mixer, etc. - may have problems with these spikes if they "pass" through the trigger.

Operational amplifiers, when overdriven, which almost always occurs at the beginning of each tone, go into a state of so-called saturation, and for a period of time before it recovers from this state (the so-called recovery time) the circuit does not work, and for this period of time (on the order of several milliseconds) we lose the signal - the tone onset. The tube (and this circuit) does not have this property, and when the signal is overdriven, it softly distorts the second harmonic, which is the octave that doesn't matter. In addition, the first signal after the peak is immediately undistorted overplayed.

The result is that the instrument "voices" so to speak (because the beginning of the note is not lost). The instrument comes through very well in a band even at lower volumes, the tone is intelligible at any correction setting, it sounds very good both in a live concert and in the studio.

- 9V battery power supply
- Current draw 1.2mA
- Battery life approx. 420 hours, up to 1000 hours when using high quality alkaline batteries.
- Basic amplification +12dB
- Bass correction: +14dB/-4dB @50Hz
- Treble correction: +14dB/-12dB @6.5kHz
- Volume of the first pickup
- Volume of the second transducer