Loba Posted December 13, 2024 Posted December 13, 2024 (edited) Disclaimer: Just your average joe who joined the product testing program and was selected to review the usage of Fosi’s soon to be launched P4 solid state Preamp with no monetary renumeration whatsoever. To begin with, I have 3 audio setups complete with discrete streamer, DAC, preamps and amplifiers in home living room, desktop and office. While I initially wanted to test P4 across all 3 setups, I eventually opted for desktop use only and I will share why. An introduction to the P4: The P4 measures W11.5 by D14cm by H4.2cm with front facing power/mode switch button accompanied by 3 knobs for volume, treble and bass adjustment. The knobs are well weighted so that you won’t accidentally increase the volume and blow your speakers OR your eardrums if you have headphone amps after P4. Both treble and bass adjustment snaps to rest at neutral (12 noon) as it should. The rear features 3 RCA inputs, 1 RCA output and 1 pre-out suitable for active subwoofers, a bypass switch to bypass tonal adjustments, a gain switch for 3dB, 6dB and 9dB. Your typical red and white RCA cables will fit with no issues but do note that if you use cables with neutrik profi spring loaded rca plugs or equivalent, it will be quite a tight fit due to the close proximity of the RCA ports. Fosi has included a remote that allows for the control of: 1. P4 2. ZD3 (released DAC) 3. ZP3 (yet to release Multichanel Preamp with XLR) and 4. BT20A MAX (yet to release I guess bluetooth amplifier) The P4 is powered by a 12V 1.5A round barrel power adaptor with a power cord length which I unfortunately neglected to measure but I would estimate it to be at about 1m so something to take note for your power cord extension positioning and one of the reasons why I have chosen to test on my desk. My setup (Yes, it’s a mess in the picture): My sources consist of the following: 1. PC -> Topping E30II or Fosi ZD3 DAC 2. Wiim Ultra streamer P4 RCA outputs to Burson Funk integrated amplifier with headphone out (V6 classic Op-amps) to Stax SRD-6 to Qacoustic 2010i speakers. P4 preamp outputs to creative i-Trigue 3400 subwoofer only. My usage: I frequently reach for the remote to turn on and off the P4 as P4’s power button requires you to press and hold to turn off. Pressing the mode button will trigger an audible relay switch sound when switching inputs. The mute button works for P4 as well which is a pleasant surprise. Pressing the button between mode and reset does gave a relay sound though I have no idea what that is supposed to do for P4. For those who intend to use the P4 not at desktop, I tested the remote effective angle of use to be about 90 degrees from the front and the range to be at least 6 meter with direct line of sight. Leaving the gain at 3dB (lower noise floor!), my P4 volume knob stays at 12noon, same position on my burson funk to drive my speakers or my headphones to acceptable listening levels. If I were to bypass P4, burson funk volume knob is about the same position to achieve the same listening levels. Update: Connecting the Shanling CR60 required me to set the gain at max of 9dB to achieve same listening volumes of streamer while leaving the volume knobs at same position. CDs are just quieter.. If I were to max the volume on P4 and lower the volume on burson funk, Wiim Ultra overdrives P4 to audible distortion especially on headphones so a word of advice, 12 to a max of 2pm on the volume for P4. In terms of testing sonic differences, I differ to using my current range of headphones; Fiio FT1, FT1 Pro and Stax SR-X MK3. I do not find noticeable differences unlike the time I used a hybrid tube preamplifier (not fosi) which introduced much distortion when volume is 10am and above on the preamplifier. This is a plus for me as that is a testament to its transparency. A frequency “complaint” on early stax headphones is the lack of bass on them. EQing the source does little to help but P4 takes stax to task boosting the bass with no audible distortion even at maximum bass boost. A great delight for niche users such as myself. P.S. Person in photo is from a group of friends who came over to audition headphones for the desktop arrangement. Final words and thoughts: Who is this P4 for? It is a perfect fit for me with multiple sources and soon to arrive Shanling CR60 CD transport to hook up to another DAC will be the 3rdsource together with PC and wiim ultra. Tonal adjustments are great to have especially if you prefer an easy way to adjust while at your desk with headphones. TL; DR If you have 3 sources, 1 amplifier to a set of passive bookshelf speakers AND an active sub woofer, this is the pre-amp/RCA switch for you with the bonus of a very usable remote and tonal adjustments. Pricing remains to be seen but anything less than US$200 would be a real bargain in my opinion. My personal wish would be for all audio equipment to be powered by USB C in future so that I would not need power adaptors and end up having 2 x 6 extension cords under my table! Edited December 13, 2024 by Loba 3
Chazz Posted December 23, 2024 Posted December 23, 2024 It would be interesting to see how this compares to the Schitt Saga 2. I have two Fosi Audio Mono v3s hooked up to a Schitt Saga 2 and they sound great. At the time Fosi did not have any preamps which had multiple inputs and I did not want a tube.
Loba Posted December 23, 2024 Author Posted December 23, 2024 (edited) On 23/12/2024 at 5:35 AM, Chazz said: It would be interesting to see how this compares to the Schitt Saga 2. I have two Fosi Audio Mono v3s hooked up to a Schitt Saga 2 and they sound great. At the time Fosi did not have any preamps which had multiple inputs and I did not want a tube. Expand ah, I have 2 v3 monos hooked up to topping pre90 with xlr in and out (I need it due to interference from too many cables from behind my cabinet. i suppose p4 u get tonal adjustments at the cost of losing xlr outputs but you may want to wait for zp3 with xlr connectivity Edited December 23, 2024 by Loba
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