Basswave amplifier

Posted on Feb 4, 2014

The JBL `Bass Wave`amplifier is a small 100-watt amplifier with built-in active filter with a single-pole high-pass at 10 Hz combined with a single-pole lowpass at 85 Hz. It costs an amazingly low $50 US. It also comes with line and speaker-level inputs and a volume control for level-matching, and an `auto signal sensing power switch`. It also fea

Basswave amplifier
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tures reasonable build quality. However, it is not an "audiophile" or even hifi-quality amplifier - a few corners have been cut in the design inorder to keep the price so low. However, it may be possible to improve it a bit with a few tweaks. The Bass Wave amplifier uses a "class-B" output stage. Most audio amplifiers use a "class-AB"output stage because class-B circuits are prone to crossover distortion, which audibly affects the output at low volumes. The notch distorion may show as a fuzziness or raspy character at very low levels. Note that this is of less consequence in a subwoofer design, as the effect is less noticeable at low frequencies, and how many times have you listened to a subwoofer at low volumes The output devices in the Bass Wave amplifier are used in a common collector configuration. While this raises the voltage gain of the stages (and is a cheap way to save parts), it also raises the output impedance, which in turn reduces the current dumping and damping factor of the amplifier. The voltage gain should come from the driver stage of the amplifier, not the output devices. (Correction - Jason Cuadra says that it is a composite 2 stage common emitter with local feedback set by R31 and R30, setting gain to 10). Bill Wilson of the DIYLoudspeakers List described the circuit design of the Bass Wave amplifier as follows in message to the List (which I`ve edited slightly here): " A low pass input network feeds...

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