Hello All,
A couple of days ago a Fosi P4 Pre-amp showed up on my front door steps. I paid $80 on sale.
I was interested in taking a look at the tone controls for a little adjustment of the bass from the JBL AC16 speakers on my bench. Voices rumble a little in the output audio of some TV series audio. More about this tone control stuff later.
I hooked the cute little Pre-Amp to the audio analyzer on my bench. There was a little 60Hz powerline harmonics in the 1 kHZ FFT plot. The little Pre-Amp went into a shielded steel box that was bonded to the ground connection on the analyzer. The PS harmonics disappeared, indicating to me the PS harmonics are not coming from the supplied switching wall-wart.
With everything OEM the 2nd and 3rd harmonics are prominent above the noise floor, yet likely not auditable. I do not know the identity of the OP-Amp.
See the attached analyzer dashboard below.
Thanks DT
A couple of days ago a Fosi P4 Pre-amp showed up on my front door steps. I paid $80 on sale.
I was interested in taking a look at the tone controls for a little adjustment of the bass from the JBL AC16 speakers on my bench. Voices rumble a little in the output audio of some TV series audio. More about this tone control stuff later.
I hooked the cute little Pre-Amp to the audio analyzer on my bench. There was a little 60Hz powerline harmonics in the 1 kHZ FFT plot. The little Pre-Amp went into a shielded steel box that was bonded to the ground connection on the analyzer. The PS harmonics disappeared, indicating to me the PS harmonics are not coming from the supplied switching wall-wart.
With everything OEM the 2nd and 3rd harmonics are prominent above the noise floor, yet likely not auditable. I do not know the identity of the OP-Amp.
See the attached analyzer dashboard below.
Thanks DT
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