Fosi Audio P4 Preamplifier Review

[antcollinet]

Yeah anyway guys and gals, as I was saying, a massive difference for the better when swapping out the op amps for the SX52B discreet op amp and upgrading the power supply. Instant likeable sound signature which impressed me a little further than the Muses 02 did in the P4. The SX52B give a notably less congested midrange by comparison, more depth to the soundstage even with the added negligible distortion as pointed out by others that mankind would not be able to discern regardless. The change in sound signature can be clearly identifiable using a resolving dac. I may try the SX35B later.

You hear the proof, not just read it.

Incidentally I never argued against the measurements in the first place or said that anything would change the device itself, just alter the sound quality and imo, for the better.

Enjoy!

Yes. Well. Anyway: AMR (audio magic review) is over that way -------->.

you appear to be lost.

 

[Schlippwhip68]

Yes. Well. Anyway: AMR (audio magic review) is over that way -------->.

you appear to be lost.

Troll camp to the left and those whom clearly have issues with those who can hear to the emergency pop up emotional support tent for a cup of tea and some words of condolance.

 

[Thighsofsteel]

Troll camp to the left and those whom clearly have issues with those who can hear to the emergency pop up emotional support tent for a cup of tea and some words of condolance.

You can’t hear anything. You ‘imagine’ you hear things.
Also it is spelt ‘condolence’ Spell checking is easy. If you can’t focus on such simple things, why should anyone believe your nonsense?

 

[Schlippwhip68]

You can’t hear anything. You ‘imagine’ you hear things.
Also it is spelt ‘condolence’ Spell checking is easy. If you can’t focus on such simple things, why should anyone believe your nonsense?

Is that right, ok. Well I guess there is no need to go any further in anything then as it all ‘imagined’ and that everyone is living in an imaginary world nothing is better than anything else ever because we all just imagine it is…gee, thanks.

 

[Thighsofsteel]

Is that right, ok. Well I guess there is no need to go any further in anything then as it all ‘imagined’ and that everyone is living in an imaginary world nothing is better than anything else ever because we all just imagine it is…gee, thanks.

Is that your response? Really? I would get that from a young teenager. Good grief.

 

[Joe Smith]

Guys, suggest respectfully we disengage. Two schools of thought on this that just can’t be reconciled… Retreat to neutral corners.

 

[Bob101]

It will most likely already have been adressed earlier in the comments, but what is the pre-amp out for? Is it the same as the RCA out, but in 3.5mm jack format? It is not in the (very short) manual...

 

[SnakeLord]

Thats what the pre-out is there for on the P4 according to Fosi:

"What can the pre-out port used for?

Allows for easy connection to external powered subwoofers or additional amplification. It ensures seamless integration with your audio system, enabling enhanced bass response or driving additional speakers for a more immersive listening experience."

Fosi Audio P4 Mini Preamplifier

Mini Control Hub: The P4 supports up to 3 RCA inputs, allowing easy connection to CD players, streamers, DACs, cassette decks, and turntables with built-in phono preamp. Switch between sources with a click for seamless audio control. Practical and User-Friendly: Equipped with volume control...

fosiaudio.com

@Bob101

 

[Bob101]

@Bob101

Is the 3.5mm output the same as the RCA outputs? Is it volume controlled, or just a pass-trough of the selected input?
I just find the concept of a 'pre-out' on a pre-amp confusing. Not seamless

 

[jmb239]

The 3.5mm output bypasses the tone controls, but not the volume pot.

 

[SnakeLord]

Is the 3.5mm output the same as the RCA outputs? Is it volume controlled, or just a pass-trough of the selected input?
I just find the concept of a 'pre-out' on a pre-amp confusing. Not seamless

Unfortunately the pre-out function on the P4 is barely documentated, the only official information i could find is the one from their website FAQ which i reffered to. Manual has no information at all.

So i would assume the pre-out jack is affected by the gain switch (1V, 2V, 4V) and the volume control same as RCA out.
This makes sense, since if you connect an additional sub to it, then you expect the signal to be matching to the RCA out.
Dunno about the tone controls.

 

[Ericco]

In case this hasn’t been posted elsewhere…

Control frequency ranges for the P4:

• Bass adjustment range: 20Hz–500Hz (±12dB)
• Treble adjustment range: 1kHz–20kHz (±12dB)

The knobs are centered at 0dB, and each ~10° turn from center adjusts the gain by approximately 1dB.

 

[jareinertson]

This works for many, and may be preferable... But in my main upstairs setup, it's a small workroom and only has one electrical outlet. For that reason, I mainly use a restored receiver or integrated amplifier, as I also have to connect turntable, lamp, computer, DAC, and sources. I rotate in my Fosi and Schiit stuff to this system, but having to plug in three things (amp, pre, phono pre) versus one integrated is less preferable.

Since it's a small room, I don't need a lot of power. Currently I use a fully restored Marantz 2216 (c.1978) with a switching input going into the AUX so I can have CD, tape, DAC and phono all available.

I admit my use case there is very specific. But given the vinyl resurgence, I continue to hope that Schiit, Fosi or someone else will have a preamp at some point that has a slot for an internal phono pre.

I do think the Fosi P4 and the Schiit Saga 2 are going to fit a much wider use case for most folks. As I use both over time in other setups, I find the main drawback of the P4 is the big volume jump at the lower end of the pot range. It's nice to have the remote, but I find the only way to adjust volume accurately at lower levels is to use the volume control on the amp (usually a Fosi or Aiyima product). The Schiit is much, much better at level matching and lower volume level adjustments.

Awesome to hear of a 2216 being restored and in use. Good for you! Go Marantz blue!

 

[ADZ]

You can't use this pre with your V3 as you say but a switching box will solve your issue and is cheaper

Something like this

https://www.amazon.co.uk/Switcher-BolAAzuL-Stereo-Selector-Passive/dp/B0CW5BJPKT/ref=asc_df_B0CW5BJPKT?tag=bingshoppinga-21&linkCode=df0&hvadid=80333258031350&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583932725391814&psc=1

Yes you can! It's a pre-amp. The V3 is a power amp. Turn the V3 volume to almost full and use only the P4 volume control. Simple!

 

[gino1961]

Hi ! sorry to jump in with the usual trivial question but i have found this in the web

The output impedance of the Fosi Audio P4 preamp is variable. It ranges between 1k and 60 k depending heavily on the position of the front volume knob

why is that ? one of my rule is constant impedance output
Could someone explain this to me ? is the pot connected to the outputs maybe ?
very very weird imho

 

[antcollinet]

Hi ! sorry to jump in with the usual trivial question but i have found this in the web



why is that ? one of my rule is constant impedance output
Could someone explain this to me ? is the pot connected to the outputs maybe ?
very very weird imho

Seems very unlikely. this is an active preamp. If it were passive it would have variable output impedance, but even then 60K would be very unlikely - it would imply a 120K pot - which would be a ridiculous choice.

I would guess someone has got their wires crossed.



EDIT - @Carl-Fosi Audio please can you give an accurate specification for the output impedance (not minimum load impedance) and state how it is measured.

Your (FOSI) not providing this clear and important data is what allows such (possible?) misinformation as posted above to proliferate.

 

[gino1961]

Seems very unlikely. this is an active preamp. If it were passive it would have variable output impedance, but even then 60K would be very unlikely - it would imply a 120K pot - which would be a ridiculous choice.

I would guess someone has got their wires crossed.



EDIT - @Carl-Fosi Audio please can you give an accurate specification for the output impedance (not minimum load impedance) and state how it is measured.

Your lack of such clear and important data is what allows such misinformation as posted above to proliferate.

Hi thank you for the very kind and valuable reply
If you just Google fosi audio p4 output impedance the above mentioned info pops up
I am a happy owner of this little marvel
I am not crazy for its too small factor but it's my problem
Instead I like its look very very much
A low output impedance would allow it to be mated with almost any power amps around
Have a nice day

 

[antcollinet]

Hi thank you for the very kind and valuable reply
If you just Google fosi audio p4 output impedance the above mentioned info pops up
I am a happy owner of this little marvel
I am not crazy for its too small factor but it's my problem
Instead I like its look very very much
A low output impedance would allow it to be mated with almost any power amps around
Have a nice day

I have just done numerous searches, including using 2 AI's and haven't found any reliable info about the output impedance.

Can you provide the link?

Thanks.

 

[gino1961]

Google Search

fosi p4 preamp output impedance

 

[antcollinet]

Google Search

fosi p4 preamp output impedance

As I said I've already searched. I've even added "60 k" to the search term. Presumably you know the actual page where the text you posted is found. Why don't you link to it?