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February 4, 2015
about 7 years ago
I just left a comment based on some math I did. The bandwidth in the product description is misleading. Gain is 3dB down at 10kHz and 6dB down at 15.9kHz. The low frequency 3dB point slightly varies based on the tripot position. It is 25Hz at 100%, 19Hz at 90%, 17Hz at 50%.
I'm buying a few of these to save time and space with some audio projects. There are a few slightly misleading things in the description. For those who are curious here are the results of some math I did.
The description states that the bandwidth is 15.9kHz. One might expect this to mean that a 15.9kHz signal is amplified 3dB less by this amplifier than a 1kHz signal--however, this is not true. The difference in gain is 6dB, since 15.9kHz is the 3dB cutoff for each stage individually. The high frequency 3dB cutoff is actually 10.1kHz. For those interested in audio applications, the gain at 20kHz is about 9dB less than in the passband.
For low frequencies a similar effect is noted. Each stage has a 3dB low frequency cutoff of about 10Hz. Therefore at 10Hz the gain is 6dB less than it is in the passband, and the actual 3dB frequency is 25Hz. At 20Hz the gain is 4dB less than in the passband.
Therefore the actual passband is from 25Hz to 10.1kHz.
All of these numbers come from using ideal op-amps for the calculations, and are based on having the trimpot at 100%. The low frequency response changes as the trimpot is adjusted, it is best at 50%, when the resistance of the two pot branches in parallel is at a maximum. At 50% the 3dB frequency is 17Hz, at either 90% or 10% it is 19Hz.
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