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Re: how can I know or calculat my amp feedback ?

213.202.68.146

In a simplified manner - measure the AC voltage on the output (speaker) - you`ll need a sinusoidal input signal (signal generator or test CD). Let`s say that is 15 Vrms. Now measure the input signal, let`s say it`s 0,5 Vrms. Now, your Af = Uout/Uin = 30. You can disconect the feedback loop (can be tricky) and measure again, or just calculate Ao, knowing Rk and Rf. Let`s say Ao=300 - for 15 Vrms out, input signal will be 50 mV. NF=Ao/Af = 10 or 20 dB.
This is simplified, we have not inserted the speaker impedance, (changes with frequency) and the internal impedance of our amp (changed with feedback),etc.; but for our amateur purposes it is "good enough"...


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