This is a review and detailed measurements of the Fosi Audio P4 budget RCA preamp. It was sent to me by the company and as of this writing, is on sale for US $80.
The look is attractive enough for the class. A momentary switch turns on the unit and cycles through inputs, with a reassuring relay click. There are tone controls with detents in the center. Finally and very surprisingly so, the volume control is motorized and activated through remote control (not shown)!!!
Back panel shows exactly what one would need in this class:
Three inputs are provided. A switch nicely bypasses the tone controls if needed. Gain settings are available from 3 to 6 and 9 dB. The only thing missing is trigger support.
Fosi Audio P4 Preamplifier Measurements
The preamp ships with the gain switch set to 6 dB so I ran the dashboard there:
This is excellent performance for the class with distortion at -114 dB or threshold of hearing. So we are noise bound:
We have a wide margin to clear 16 bit audio without impacting its noise floor. Moreover, performance is almost maintained even at highest gain.
We can see the effect of gain on distortion+noise:
IMD test shows exemplary performance when compared to much more expensive reference up to 1 volt output:
Frequency with or without tone control bypass is excellent:
Crosstalk is very good:
As is wideband noise+distortion vs frequency:
Conclusions
The Fosi P4 surprises with incredibly low cost while providing features such as motorized volume control and excellent performance. It simply has no weak point, other than absence of trigger. This is what happens when a company is laser focused on customer needs and excellence in engineering.
I am happy to recommend the Fosi P4 to many of you who need to switch between multiple unbalanced/RCA sources.
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As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The look is attractive enough for the class. A momentary switch turns on the unit and cycles through inputs, with a reassuring relay click. There are tone controls with detents in the center. Finally and very surprisingly so, the volume control is motorized and activated through remote control (not shown)!!!
Back panel shows exactly what one would need in this class:
Three inputs are provided. A switch nicely bypasses the tone controls if needed. Gain settings are available from 3 to 6 and 9 dB. The only thing missing is trigger support.
Fosi Audio P4 Preamplifier Measurements
The preamp ships with the gain switch set to 6 dB so I ran the dashboard there:
This is excellent performance for the class with distortion at -114 dB or threshold of hearing. So we are noise bound:
We have a wide margin to clear 16 bit audio without impacting its noise floor. Moreover, performance is almost maintained even at highest gain.
We can see the effect of gain on distortion+noise:
IMD test shows exemplary performance when compared to much more expensive reference up to 1 volt output:
Frequency with or without tone control bypass is excellent:
Crosstalk is very good:
As is wideband noise+distortion vs frequency:
Conclusions
The Fosi P4 surprises with incredibly low cost while providing features such as motorized volume control and excellent performance. It simply has no weak point, other than absence of trigger. This is what happens when a company is laser focused on customer needs and excellence in engineering.
I am happy to recommend the Fosi P4 to many of you who need to switch between multiple unbalanced/RCA sources.
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
