Fosi Audio P4 Preamplifier Review

[letit08]

hi ! i would use a separate phono preamp and send its outs directly to the audio interface inputs
i would try a battery powered one ... even very cheap even diy

I already have a phono preamp ! There are other sources besides the turntable...
My question : Can we use the 3.5mm pre-out jack as an output for recording ?

 

[gino1961]

Yes of course
You just put unnecessarily another unit and cables in the recording chain
I would try with and without the P4 and listen

 

[kinski]

Hi, I’ve been running a pair of V3 monos. Love them! I keep them in auto mode. Is there a way to get the P4 preamp to auto turn on/off like the V3 monos?

 

[SnakeLord]

Hi, I’ve been running a pair of V3 monos. Love them! I keep them in auto mode. Is there a way to get the P4 preamp to auto turn on/off like the V3 monos?

The P4 has no signal auto-sensing or in/out triggers for power switch controls.

So there is no way to auto turn on/off the device or control the power switch of other devices down the chain.

 

[SnakeLord]

I already have a phono preamp ! There are other sources besides the turntable...
My question : Can we use the 3.5mm pre-out jack as an output for recording ?

Unfortunately the use of the pre-out jack is not explained in the product manual but there is some information on the Fosi webpage. Whatever it means in your use case, you should be able to figure it out.

"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

 

[KurtKlötentreter]

Unfortunately the use of the pre-out jack is not explained in the product manual but there is some information on the Fosi webpage. Whatever it means in your use case, you should be able to figure it out.

"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

I use the pre out for my subwoofers, since it's volume control is tied to the main RCA out. Although I have not tested whether it applies tone control to the pre outs too, since I barely use the tone control on the P4 and mostly leave it on bypass. I think it's probably not the ideal way to record from the pre out then, since I assume fixed gain would be more preferable in that case.

 

[beaker152]

i've been very happy with my p4 since i got it last april, but today it became uneesponsive to the remote. i swapped batteries, pointed remote at my
iphone camera and saw violet flashes, but i get no sign of recognition from the p4. line of sight is clear, power cycle was ineffective.

has anyone had problems with its IR reception?

 

[jmb239]

i've been very happy with my p4 since i got it last april, but today it became uneesponsive to the remote. i swapped batteries, pointed remote at my
iphone camera and saw violet flashes, but i get no sign of recognition from the p4. line of sight is clear, power cycle was ineffective.

has anyone had problems with its IR reception?

Maybe push P4 on the remote?

 

[beaker152]

Maybe push P4 on the remote?

when david letterman would say something particularly clever, he would sometimes say "there is no off position on the genius switch"

i tried that line on a friend of mine once and without missing a beat he replied "there is, however, a low battery condition"

pushing the p4 button was the secret.

thanks!

 

[Ericco]

@norman bates
I'd like to find reviews saying "better than my mcintosh / Audio research / etc preamp".
Or "hooked it up to my $2000 - $5000 bryston (or whatever), blows me away....................

Here you go. My Bryston sp1.7 that I used as a stereo pre bit the dust so l hooked up the P4 to my Bryston 3b a few days ago. I can’t say it sounds “as good” to my ears as the Bryston pre, but it is certainly acceptable, especially for the money. I feel the bass is kind of flabby/woofy so a high pass filter or other eq might help. It’s only been a few days so I have more work to do with it.

 

[Ericco]

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.

Can you comment on any sound impressions between the P4 and Saga 2? I’ve got a P4 and am considering the Saga. I find the P4 a little loose/flabby in the bass and the tone control doesn’t correct it. Thanks!

 

[RandomEar]

Can you comment on any sound impressions between the P4 and Saga 2? I’ve got a P4 and am considering the Saga. I find the P4 a little loose/flabby in the bass and the tone control doesn’t correct it. Thanks!

Both of them have a ruler flat frequency response and negligible distortion. Unless the tone controls on the P4 are off-center or defective, none of these preamps will have any influence on the sound.

They have one very simple job: Sound comes in -> Exactly the same sound comes out at a slightly higher voltage.

There's just one possible catch: If the input impedance of your amp is low (bad design!), the output impedance of the preamp becomes relevant and this will alter the bass response. This should never be the case, though.

 

[gino1961]

P4 output impedance is about 1kohm? why so strangely high ?
100 ohm would be more than enough to driver properly almost any line stage

 

[Schlippwhip68]

P4 with an upgraded volume dial. Managed to find this on Ali Express. Aluminium but not at all heavy. Some are solid Aluminium with just the shaft milled out which makes them quite heavy. I avoid that type of weight on these potentiometers, especially motorised like the P4. This one is the shell type with a plastic skeleton thus far lighter and in turn putting little to no weight on the potentiometer which prolongs the life of the motor and shaft seals.

I think it looks better too, a touch more maturity than just the ‘orange knob’. The ring is still orange, which is great.

This little preamp performs so well with my Audiolab M-PWR power amp. I use a Muses 02 in the P4 of which is an excellent chip for gaming! Having the extra RCA inputs allows me to rig my Benq Monitor to the P4 via headphone out as well as other sources. The audio results when gaming are again excellent with this pre amp. The voices are clean, no veiling of any kind or overly warm frequencies which you might find with Valves and so all those ‘gaming’ details are clearly there like footsteps from a distance, whispers, gun shot direction etc. The Muses 02 has a darker background than many and is very precise on intro and outro on notes with excellent frequency separation so again for gaming this is important for precise location of opponents etc and provides a very accurate vocal representation which is also great for live co-op mission.

Literally no need for a dac here!

Nice one Fosi!

 

[Schlippwhip68]

Can you comment on any sound impressions between the P4 and Saga 2? I’ve got a P4 and am considering the Saga. I find the P4 a little loose/flabby in the bass and the tone control doesn’t correct it. Thanks!

Try a Muses 02 in the P4 if you can. I find the bass on the NE5532 a little ‘loose and flabby’ less defined by comparison in everything.

You could go as far as the opa828 if you want or need specific superior bass control, that op amp hangs onto the bass like a Pit Bull on a Rabbit sandwich!

Superb control from either one of these op amps and don’t let anyone tell you they will not make a difference, they will!

 

[solderdude]

How do those op-amps do that ?

 

[SnakeLord]

How do those op-amps do that ?

Like this.

 

[gino1961]

Hi and sorry to disturb ... I'm wondering if anyone has analyzed the circuit and found an output resistor that raises the output impedance.
And I'm wondering if placing a 20-30 ohm resistor in parallel could lower the output impedance.
I have an amp with a 5 kohm only input that I'd like to use with the P4.
Albarry M408 Mono

 

[Schlippwhip68]

How do those op-amps do that ?

If I knew I would probably be making my own.

 

[Schlippwhip68]

Like this.

lol…