|Class D Switching Power Amplifiers and Power D/A conversion|
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|8th May 2011, 09:33 AM||#1|
Join Date: Jun 2010
Input DC offset? (TA2020)
Just cased a TA2020 pcb from Helder audio. While I was measuring/checking everything I noticed something that may be perfectly normal, however, would like to check in case it could harm my preamp.
Upon turning on the amp (without speakers and source) there is a 2.5v dc voltage between Input and Input Ground. Draining I and Ig with a resistor and this input offset goes and stays at 0v (draining the input capacitor I assume?)
Turning off the amp the voltage reverses:
- if voltage between I and Ig was the 2.5v from turn on, it drops to 0v
- if voltage between I and Ig was zero because I drained with resistor, voltage drops to -2.5v
With no source and speakers connected I can trim the dc offset on the outputs to zero.
Should I be worried? Or is it normal for input cap to charge at power up? And why does the voltage reverse after power down?
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