Fosi Audio P4 Preamplifier Review

[FFR]

I still have one of these from back in the day. View attachment 436397

 

[Cbdb2]

It's a shame it's not a Bluetooth remote, so it could be tucked away in a cupboard, out of view.

Or have a IR input so an external eye could be used.
If I was to quibble I would prefer the tone bypass on the front or a LED indicator so you can see if the tone controls are on without getting behind a rack. Even better would be tone controls that can be switched on/off by the remote.

 

[Cbdb2]

Is the P4 mode button on the remote just to tell it your using it with a P4?

 

[Crook]

I bought one on release, so I've been waiting for this review. It operates nicely, look and feel are really good and it measures great for not much money. It has a 3.5mm out too. The only criticisms I have is I'd prefer 3 in 2 out (2nd out fixed) and that the motorised control increases volume in too high increments on a press of the remote, half the volume for each press would be better. Minor quibbles though.

 

[Crook]

Hello,
I'm new to this forum and I thank all the participants who do a fantastic job of evaluating and providing feedback.
Perhaps this type of device is aimed at people like me who aren't looking for perfection, especially at US$80.
I currently have a FOSI V3 STEREO ((48 V/5A), which I enjoy enormously. I listen to classical music (95%) at moderate volumes in a small 15 m² living room. Passive speakers, no subwoofer, no headphone and to make matters worse, all this with 64-year-old ears.
The only problem with the V3: only one input, while I have three sources: a CD player, a DAC streamer, and a tuner. If I want to switch between them, I have to change RCA cables.
Would the P4 be a good solution in my case? I don't know anything about technology, but I read somewhere that it is not recommended to put a preamp and an integrated device in series. I will end up with two devices each with a volume controller.
I also read that it was possible to set the V3 amp at the 3:00 position, then turn up the preamp controls to the desired listening level or turn the V3 volume to maximum and use the P4 volume to control the sound level. Will this work properly without degrading sound quality ?
In France :
Incoming restock
04 - 11 April

Hi, I use my P4 with a V3 currently. It works well. I max the volume on the V3 and control volume using the P4 remote. It's all in a cabinet, so I got an IR blaster to use remote with cabinet doors closed.

 

[Bruce Morgen]

the motorised control increases volume in too high increments on a press of the remote

This is a fairly generic issue with motorized potentiometers -- at low levels, my 35+ year old Yamaha processor is pretty much useless for small volume increments when its seven-gang pot is turned via its remote.

 

[antcollinet]

You can't use this pre with your V3

Why not - turn the amp volume control to max, and use the preamp to control the volume.

You then have added remote volume control, and RCA switching, plus tone control if you want it.

 

[shuppatsu]

The numbers look good, but I don’t like cycling inputs and power.

 

[Gremlins]

a "balance" is essentially useful, coupled with a mono function...
(I'm afraid that in recent decades it has been a bit forgotten balance/mono (or the funny forgotten function of the Denon 70s...."null balance"..useful))

Hi

I have seen this null balance button on a Denon amp, what is the use of it?

 

[morillon]

Hi

I have seen this null balance button on a Denon amp, what is the use of it?

electric create an out-of-phase which allows the balance to be finely adjusted to compensate for the differences... (found sound cancellation)
The idea is simple, fast, but effective....
music playing... mono, press the button null and use the balance to find the sound cancellation point ( electronic level not acoustic )... found, release...
( pma-500z or 700z etc)

 

[Mart68]

Why not - turn the amp volume control to max, and use the preamp to control the volume.

You then have added remote volume control, and RCA switching, plus tone control if you want it.

Didn't think V3 had an input for that but if it does, then yes, no problem.

 

[morillon]

(
not to mention the "null balance "of denon... I'm not sure that Wiim streamer owners realize the interest of the balance num and mono function that they have had since almost the beginning... other more ambitious streamers do it I hope (?)
;-)
)

As for this little fosi...
an observation of the balance of the channels on the travel of the potentiometer and its output impedance would be interesting , and important (balance if pot is analogue)
;-)

 

[broe]

I would like to know what the input impedance is. I did not find any information about this. I use mostly vintage tuner for example which ree not able to drive low input mpedances.
Who can help?

 

[morillon]

I would like to know what the input impedance is. I did not find any information about this. I use mostly vintage tuner for example which ree not able to drive low input mpedances.
Who can help?

(
What tuners/ so hight output impedance(?) are you thinking of?
;-)
)

"""input and output impedance""
?

;-)

 

[broe]

(Tube Tuners usually have high output impedances.) But this was not my question. I am more concerned that my tuners are not able to drive a low input impedances.

Usually preamps had impedances > 10 to 20 kohms. Preamps from new chinese manufactureres have very low input impedances from just a few kohms that give better values for S/N.

Any information?

 

[morillon]

(Tube Tuners usually have high output impedances.) But this was not my question. I am more concerned that my tuners are not able to drive a low input impedances.

Usually preamps had impedances > 10 to 20 kohms. Preamps from new chinese manufactureres have very low input impedances from just a few kohms that give better values for S/N.

Any information?

I discovered that "Chinese" preamps can have input impedances lower than 10kohm sometimes.. surprising indeed...


so ..input and output impedance?
;-)


(the output impedances of the tuners that concern you?)

 

[antcollinet]

Didn't think V3 had an input for that but if it does, then yes, no problem.

It doesn't. You are remote controlling the pre-amp volume.

 

[Mart68]

It doesn't. You are remote controlling the pre-amp volume.

Sorry I am lost here. Maybe I am being a bit dense but it is Sunday morning and I'm only just starting on my third pint of tea.

The V3 is an integrated amp so to use a separate pre-amp with it would it not need the ability to separate the pre and power stages? I looked at the review of it on here and it doesn't seem to have that function.

 

[Ropeburn]

Sorry I am lost here. Maybe I am being a bit dense but it is Sunday morning and I'm only just starting on my third pint of tea.

The V3 is an integrated amp so to use a separate pre-amp with it would it not need the ability to separate the pre and power stages? I looked at the review of it on here and it doesn't seem to have that function.

There is no reason you can't run one preamp stage (the P4) into another (the V3's). You don't need to seperate pre and power stages on the V3. What for?

 

[Mart68]

There is no reason you can't run one preamp stage (the P4) into another (the V3's). You don't need to seperate pre and power stages on the V3. What for?

You're right of course. It's not an elegant solution but it will work, just ignore me