This headamp is purchased from TaoBao for less than $30.00. This is a model you can find from many sellers. Who is the original?
The circuit is based on 5532 + 139/140 output buffer. It has a UPC1237 based delay circuit as well. Connecting my AKG headphone, input grounded and volume at max position, I can't hear any background.
The output residual noise measured is 3 uVrms (AP S1 BW = 22 kHz, load = 333R). Bandpass measurement for the noise floor and FFT of 1 kHz test show for various output levels are shown in the figures.
The circuit is based on 5532 + 139/140 output buffer. It has a UPC1237 based delay circuit as well. Connecting my AKG headphone, input grounded and volume at max position, I can't hear any background.
The output residual noise measured is 3 uVrms (AP S1 BW = 22 kHz, load = 333R). Bandpass measurement for the noise floor and FFT of 1 kHz test show for various output levels are shown in the figures.
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