JEnglishSmith
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My Impressions of the New Fosi Audio P4 Solid-State Preamplifier
At Last! The Fosi Audio development team kindly shipped me a release sample of the new P4 preamplifier in mid-December. I'd been advocating for the need for such a preamplifier for some time, as an ideal companion for last year's V3 stereo amplifier, as well as other products Fosi has released in the meantime. I'm so glad to see this product come forward in development and be available for Fosi users.
The preamplifier was provided to me free of charge, and what follows is my honest and unrestricted take on the product. I have not been paid for any of my review comments. I don't have equipment for measurements of the unit, and I do hope they send one on to Amir for testing.
A Bit About Me
I am a pretty typical audio user living in the Midwest in the United States. I have a wide variety of audio equipment, including vintage, restored vintage, and modern. I enjoy "mixing and matching" old and new products to get the sound I want and the aesthetics I want in our 1916 home, which has many smaller rooms, which in turn has led me to having many different audio setups running at any one time.
Most of my amp needs are 100 wpc stereo at 8 omhs, or less. I normally listen at low or moderate volumes. I use a full range of sources - streaming/DAC, phono, cassette tape, CD, very occasionally FM radio. So while I enjoy the new single-input class D amplifiers, I either have to be switching jacks to sources regularly, use a simple & cheap switch box with multiple inputs/one output, or a proper preamplifier, ideally one that has both a phono preamplifier as well as line inputs.
I don't use balanced (XLR) connections in my setups, as everything has very short cable runs, and I don't use any tubes in any of my signal chains - I'm not a fan of harmonic distortion/overtones and prefer the cleanest signal I can get for a reasonable amount of money.
The recent run of inexpensive class D amplifiers has been a major boon in my audio life, as my goal in many cases is to have a simple, unobtrusive, low to mid volume system that does not take up a lot of room. I currently use class D amplifiers from Fosi, Aiyima and SMSL in our dining room, bedroom and sunporch, occasionally in my main workroom system. But in most of these cases, having a simple RCA preamplifier with multiple inputs would be very helpful.
Enter the P4!
The P4 is exactly what I was hoping for in a nice, clean, solid-state preamp that would pair nicely with the V3 stereo amp, or with other "black box" class D amps. Fosi has a nice design aesthetic going with clean case design, minimal lettering and indices, with the only "flash" provided by their distinctive (optional) copper volume knob.
The P4 has a metal case matching the recent Fosi amp releases. It's just a little larger than the V3 amp - it is 4.5" wide, just .25" wider than the V3. Thus, they would easily be stackable, with the P4 on the bottom. I've chosen to use them side by side as you can see in the photos.
The nice feature set from Fosi includes tone controls (bass and treble) on the front panel, with a plus or minus 12 db range, and a tone defeat switch located on the back of the unit. There is an adjustable slider-type gain switch on the back of the unit that lets one select 1v, 2v or 4v gain, corresponding to +3db, +6 db, or +9 db. There is also a pre-out jack which I assume can be used for a powered subwoofer connection - I don't use one, so I can't test this feature. (The manual does not provide guidance on this feature.)
And - a nice remote control! The remote is comfortable to hold and apparently can be used for multiple Fosi products, including the ZD3, ZP3 and BT20A MAX as well as the P4. The remote is nicely laid out with a power button, mute, volume, back/forward keys, mode selection, reset button and switch device buttons. It is powered by two AAA batteries (not included).
Power is provided by a wall-plug type power adapter, a small one, that is rated at DC 12v 1.5a. It terminates in a barrel plug that goes into the unit.
I've used the remote to power up the P4 and adjust volume. One can turn on the P4 by pressing and holding the volume knob, or pressing longer to turn it off, but it's simpler to use the remote. The remote seems to work from a reasonable distance away from the unit.
So, the P4 definitely checks most of the feature boxes I as a user was looking for - 3 RCA inputs, a good remote, adjustable bass/treble, tone defeat option, adjustable gain levels, and a compact size.
So, How Does It Sound?
In a word - great! The sound reflects the unit's claimed equal or better than 110 db SNR, 0.003% THD, low noise floor (+/- 9 uV) and equal or better than 103 db crosstalk.
Even at the lowest gain setting, there is a nice sound boost from the V3 amp alone, and very very loud indeed at the highest setting. Right now, for comfortable listening volume, I am on the lowest gain setting, the V3 power knob is at 75% and the P4 volume knob is at 50% with my older KEF Q 15.2 speakers (rated at 91 db efficient). Sample track I'm playing is between 75 and 85 decibels in nearfield, approximately a meter and a half from speakers. (I use a 36v 6a power supply for the V3 amplifier, as I really have no need for a 48v supply with the room sizes I have.)
I am not aware of any noise coming from the P4. With nothing playing, the above settings cause no speaker noise or hiss.
The adjustable tone controls are very handy. I use speaker EQ now via Equalizer APO to smooth out the KEFs a bit, but I like to leave that as a base setting and not fiddle with the computer/streaming settings. But when listening at low volumes, I do like to be able to adjust bass and treble, similar to the old "loudness" circuit on vintage equipment. It's helpful to just have a basic EQ control without having to buy an entirely separate unit for that, such as the Schiit Loki.
The P4 adds a surprising amount of power given the very small size of its power brick (18 watts). Playing as noted above, the P4 is cool to the touch and the V3 is barely warm after playing for many hours.
I regularly listen to a wide range of music - jazz, blues, rock, folk, electronic/ambient and classical. The P4 sounded just great with everything I played.
Pros and Cons
So let me note my main plusses and minuses about this unit for your consideration.
Pros:
I'm glad that Fosi now has a good, simple and design-coherent preamp solution to match for its power amps for those of us that are only using RCA cabling. I understand they are also developing a product for the balanced/XLR users.
It's a very solid entry and I think it fills a big product gap for people using multiple inputs and not having access to a legacy, powered preamp as in days of old. Three is enough for most. If using phono, just connect using a dedicated phono preamp before one of the P4 inputs. Then an input for CD and an input for DAC/streaming. That's probably going to be enough for 95% of current audio enthusiasts.
The P4 follows the current releases of class D amplifiers with a "less is more" kind of philosophy. The big boxes of my youth have been replaced by small boxes that don't cost an arm and a leg and sound really, really good. It's an exciting time to be enjoying audio, for sure!
Watch for the release date and pricing for the P4 soon!
At Last! The Fosi Audio development team kindly shipped me a release sample of the new P4 preamplifier in mid-December. I'd been advocating for the need for such a preamplifier for some time, as an ideal companion for last year's V3 stereo amplifier, as well as other products Fosi has released in the meantime. I'm so glad to see this product come forward in development and be available for Fosi users.
The preamplifier was provided to me free of charge, and what follows is my honest and unrestricted take on the product. I have not been paid for any of my review comments. I don't have equipment for measurements of the unit, and I do hope they send one on to Amir for testing.
A Bit About Me
I am a pretty typical audio user living in the Midwest in the United States. I have a wide variety of audio equipment, including vintage, restored vintage, and modern. I enjoy "mixing and matching" old and new products to get the sound I want and the aesthetics I want in our 1916 home, which has many smaller rooms, which in turn has led me to having many different audio setups running at any one time.
Most of my amp needs are 100 wpc stereo at 8 omhs, or less. I normally listen at low or moderate volumes. I use a full range of sources - streaming/DAC, phono, cassette tape, CD, very occasionally FM radio. So while I enjoy the new single-input class D amplifiers, I either have to be switching jacks to sources regularly, use a simple & cheap switch box with multiple inputs/one output, or a proper preamplifier, ideally one that has both a phono preamplifier as well as line inputs.
I don't use balanced (XLR) connections in my setups, as everything has very short cable runs, and I don't use any tubes in any of my signal chains - I'm not a fan of harmonic distortion/overtones and prefer the cleanest signal I can get for a reasonable amount of money.
The recent run of inexpensive class D amplifiers has been a major boon in my audio life, as my goal in many cases is to have a simple, unobtrusive, low to mid volume system that does not take up a lot of room. I currently use class D amplifiers from Fosi, Aiyima and SMSL in our dining room, bedroom and sunporch, occasionally in my main workroom system. But in most of these cases, having a simple RCA preamplifier with multiple inputs would be very helpful.
Enter the P4!
The P4 is exactly what I was hoping for in a nice, clean, solid-state preamp that would pair nicely with the V3 stereo amp, or with other "black box" class D amps. Fosi has a nice design aesthetic going with clean case design, minimal lettering and indices, with the only "flash" provided by their distinctive (optional) copper volume knob.
The P4 has a metal case matching the recent Fosi amp releases. It's just a little larger than the V3 amp - it is 4.5" wide, just .25" wider than the V3. Thus, they would easily be stackable, with the P4 on the bottom. I've chosen to use them side by side as you can see in the photos.
The nice feature set from Fosi includes tone controls (bass and treble) on the front panel, with a plus or minus 12 db range, and a tone defeat switch located on the back of the unit. There is an adjustable slider-type gain switch on the back of the unit that lets one select 1v, 2v or 4v gain, corresponding to +3db, +6 db, or +9 db. There is also a pre-out jack which I assume can be used for a powered subwoofer connection - I don't use one, so I can't test this feature. (The manual does not provide guidance on this feature.)
And - a nice remote control! The remote is comfortable to hold and apparently can be used for multiple Fosi products, including the ZD3, ZP3 and BT20A MAX as well as the P4. The remote is nicely laid out with a power button, mute, volume, back/forward keys, mode selection, reset button and switch device buttons. It is powered by two AAA batteries (not included).
Power is provided by a wall-plug type power adapter, a small one, that is rated at DC 12v 1.5a. It terminates in a barrel plug that goes into the unit.
I've used the remote to power up the P4 and adjust volume. One can turn on the P4 by pressing and holding the volume knob, or pressing longer to turn it off, but it's simpler to use the remote. The remote seems to work from a reasonable distance away from the unit.
So, the P4 definitely checks most of the feature boxes I as a user was looking for - 3 RCA inputs, a good remote, adjustable bass/treble, tone defeat option, adjustable gain levels, and a compact size.
So, How Does It Sound?
In a word - great! The sound reflects the unit's claimed equal or better than 110 db SNR, 0.003% THD, low noise floor (+/- 9 uV) and equal or better than 103 db crosstalk.
Even at the lowest gain setting, there is a nice sound boost from the V3 amp alone, and very very loud indeed at the highest setting. Right now, for comfortable listening volume, I am on the lowest gain setting, the V3 power knob is at 75% and the P4 volume knob is at 50% with my older KEF Q 15.2 speakers (rated at 91 db efficient). Sample track I'm playing is between 75 and 85 decibels in nearfield, approximately a meter and a half from speakers. (I use a 36v 6a power supply for the V3 amplifier, as I really have no need for a 48v supply with the room sizes I have.)
I am not aware of any noise coming from the P4. With nothing playing, the above settings cause no speaker noise or hiss.
The adjustable tone controls are very handy. I use speaker EQ now via Equalizer APO to smooth out the KEFs a bit, but I like to leave that as a base setting and not fiddle with the computer/streaming settings. But when listening at low volumes, I do like to be able to adjust bass and treble, similar to the old "loudness" circuit on vintage equipment. It's helpful to just have a basic EQ control without having to buy an entirely separate unit for that, such as the Schiit Loki.
The P4 adds a surprising amount of power given the very small size of its power brick (18 watts). Playing as noted above, the P4 is cool to the touch and the V3 is barely warm after playing for many hours.
I regularly listen to a wide range of music - jazz, blues, rock, folk, electronic/ambient and classical. The P4 sounded just great with everything I played.
Pros and Cons
So let me note my main plusses and minuses about this unit for your consideration.
Pros:
- Very nice case and control aesthetics and matching with the V3 and rest of the Fosi amp families, including the fun copper knob!
- Great, easy to use remote including input selection and muting.
- Lots of power boost and switchable gain levels.
- Simple to use tone controls and inclusion of a tone defeat switch.
- Decent channel matching at lower volume levels - will be nice to see formal testing on this, but sounds good to my ears.
- Great overall specs, minimal amount of noise inserted into the music chain.
- Price? Fosi has not told me the release price for this unit. In comparison, the new black Saga 2 preamp from Schiit has four inputs, 3 adjustable gain modes, class A power with a custom power brick, good/metal remote, a headphone jack, and a very precise relay-based volume control system, and it's priced at $279. So I feel there's a price range where the V4 will do well, but if it gets too close to the Schiit product, it's a harder call. Of course, for those wanting to always stay in the Fosi family of products, it's an easy call!
- The use of the pre-out jack is not explained in any way in the product manual - Fosi should provide some additional guidance on this.
- The gain switch feels a bit flimsy - like it could break if used repeatedly - not a problem for me, as I'm probably going to use at the 1v or 2v settling and just leave it alone - but if your use case would have frequent switching going on, I'd wonder a bit about the longevity.
- The bass and treble knobs are very close to the volume knob - a bit close - even with my normal size hands, you brush them when adjusting the volume via the knob. I understand the desire to have the case not get much wider than the V3 amp, but the spacing is a bit tight. Not a huge problem, as I expect most folks will be adjusting the volume via the remote?
- No purely passive gain mode (0 gain) - this is a nice feature of Schiit's recent Saga 2 preamplifier - I won't use that often, but it’s nice to have the option.
- When using the remote, the volume really jumps in the lower volume range - not a lot of range at the lowest volume level. However, this can be improved by hand-turning of the knob, and even easier is to use the V3's volume knob to "dial in" a precise low volume setting. The V3 volume pot in general feels more precise than the P4 in the lower volume range. This is one area that disappoints me just a bit. The Schiit Saga 2 preamp has a relay attenuator volume system that is extremely precise for both volume control and channel matching, which is very nice for users like me who often play at lower and background volumes.
- No headphone jack & associated electronics to allow for - this would have been nice to have. The Saga 2 has one.
- No dedicated phono preamp circuit. (Impossible for a case this size and for the probable price point, Schiit passed on this too. This is one area where the vintage/legacy preamps do have great feature sets – I own a few (NAD 1020, Nikko Beta 20) – but of course the internals are 30+ years old and they do add more noise to my chain if I use them. And many current vinyl users will either use their table’s internal phono preamp (on the inexpensive side) or have a dedicated separate phono pre (cheap to ‘sky’s the limit’) so this is probably not going to be a problem for most.)
- Another power brick - albeit a small one - I personally would have preferred inside power, but probably no way to do in the case size they wanted.
- Nitpick 1: The mute button on the remote is very close to the power switch. Easy to miss-press.
- Nitpick 2: The V3 amplifier's LED is blue. The mode LED on the P4 is red/orange. Would be nice for Fosi to standardize the LED color for system coherence. Same with the front silkscreening, slightly less bright than my V3 amp.
- Nitpick 3: The spacing on the back jacks are pretty tight. Normal RCAs work fine. Wide ones might be a bit of a squeeze (see photo).
I'm glad that Fosi now has a good, simple and design-coherent preamp solution to match for its power amps for those of us that are only using RCA cabling. I understand they are also developing a product for the balanced/XLR users.
It's a very solid entry and I think it fills a big product gap for people using multiple inputs and not having access to a legacy, powered preamp as in days of old. Three is enough for most. If using phono, just connect using a dedicated phono preamp before one of the P4 inputs. Then an input for CD and an input for DAC/streaming. That's probably going to be enough for 95% of current audio enthusiasts.
The P4 follows the current releases of class D amplifiers with a "less is more" kind of philosophy. The big boxes of my youth have been replaced by small boxes that don't cost an arm and a leg and sound really, really good. It's an exciting time to be enjoying audio, for sure!
Watch for the release date and pricing for the P4 soon!
