BiAmpPro – Bench Testing

The BiAmpPro is a one-stop solution to convert your 2-way speakers to active. On board is the power supply comprising of an 8A bridge rectifier and 4 pieces of 3,300uF/25V filter capacitors. Apart from supplying power to the TDA2030A and the TDA2050 chip amps, it also powers the op amp through two voltage regulators, 7812 and 7912. The input is Balanced with a provision to adjust the output of the tweeter to match the woofer. For extra power, two TDA2050 are used in mono-bridge.

What is unusual with this BiAmpPro is the crossover. Instead of using op amps, the crossover is part of the chip amps. This is called “Active Power Speakers” by the manufacturer, SGS Thomson. The diagram below shows the BiAmpPro with the implementation of this active power crossover. Note that this is not the same as Passive Line Level Crossover, better known as PLLXO.

In this BiAmpPro, I set the High Pass crossover at 2,500Hz. This is an optimum frequency for 1″ tweeter. Any other crossover frequencies can be set, like 3kHz or 3.5kHz for 3/4″ tweeters. Simply solder in another combination of resistors and capacitors.

Tweeter Output Power into 4Ω with 2.5kHz HP

10kHz Full Power into 4Ω

10kHz Square Wave into 4Ω

All tweeter measurements are with a 12dB High Pass filter at 2.5kHz in place. The plot on the left is at 10kHz. The sine wave is clean all the way to just before clip. Maximum voltage swing into 4Ω is 20Vp-p. The right plot is a 10kHz Square Wave. The downward tilt at the trailing edge indicates the low frequencies are rolled off by the crossover.

Woofer Output Power into 4Ω with 2.5kHz LP

1kHz Full Power into 4Ω

1kHz Clipped Wave into 4Ω

The woofer plots are with a 12dB Low Pass filter of 2.5kHz. The left plot is the Full Power output at 1kHz. The right plot shows the clipping waveform when it is over-driven. There are no signs of instability.

BiAmpPro Specifications

Tweeter Power Output = 12W into 4Ω
Woofer Power Output = 24W into 8Ω (mono-bridge)
Woofer Input Sensitivity (@ 1kHz before Clip) = 0.35V RMS into 8Ω (Bal) | 0.7V RMS into 8Ω (UnBal)
Voltage Gain = 27dB

Power Supply Specs
Power transformer = 12-0-12Vac
Supply Rails = +/- 16Vdc
PSU caps = 13,200uF (4 pcs of 3,300uF / 35V)

Conclusion

So far, the measurements look good but as all things with audio, I have to listen to it. I will need to use one of my 2-ways, remove the passive crossover and power it up with the BiAmpPro. It’ll be interesting to see how well the TDA2030A and the mono-bridged TDA2050 sound like with their special crossovers.