Avvocato
New member
After spending a few weeks with the Fosi Audio ZP3 preamplifier, I wanted to share my detailed thoughts and experiences. I know there's been a lot of discussion about this unit, and I hope my perspective can help others who might be considering it. My system context is a bit specific, which I believe makes this review particularly relevant for a certain type of user.
Introduction: Setting the Stage – My System and the Search for a Control Center
The Current Setup To understand my evaluation of the ZP3, you first need to understand the system it was dropped into. My setup is built around a philosophy of high-efficiency and high-value performance. The heart of the system is the Fosi V3 power amplifier, a little giant that I’m sure many of you are familiar with. It’s a clean, powerful, and ridiculously good amp for the money. Even on its own, the V3 has a very low noise floor, which made it a good match for my speakers.
The V3 drives a pair of custom high-sensitivity bookshelf speakers, the Audiojam2, designed and built by Alberto Bellino. These speakers are incredibly revealing. With their high sensitivity, they act like a sonic magnifying glass for everything upstream in the audio chain. Any noise, any hiss, any subtle coloration introduced by a component is immediately laid bare. While this makes them a joy for critical listening, it also makes them ruthlessly unforgiving of noisy or subpar electronics. My sources are a Topping DAC for digital files and a turntable running into a separate phono stage for vinyl.
The Problem to Solve My minimalist setup, while sonically pure, had some significant practical limitations.
When Fosi announced the ZP3, it seemed like it was designed specifically for me. On paper, it was the perfect solution. It was marketed as a "Versatile Control Hub for Home Audio Systems," which is exactly what I needed. It offered multiple inputs (two RCA, one XLR) to solve my cable-swapping problem, a remote control for volume, and most importantly, an adjustable High-Pass Filter (HPF). The specs were incredible for its $199.99 price point, and the promise of synergy with my existing Fosi V3 was too good to ignore. I placed my order with high hopes that this would be the final piece of my audio puzzle.
Unboxing and Physical Impressions: A Step Up for Fosi
Right out of the box, the ZP3 makes a strong impression. Fosi has been steadily improving its build quality, and this unit feels like a significant step up.
Build Quality and Aesthetics The chassis is a solid, unibody aluminum alloy construction that feels dense and substantial in the hand. Fosi claims this all-metal build provides superior shielding from interference, and based on the heft and seamless construction, I believe it. The main body has the standard Fosi flat black, matte finish, but the side panels are a contrasting shiny black, which is an interesting, if slightly unusual, design choice.
The front panel controls have a satisfying tactile feel. The bass, treble, and balance knobs have a smooth, nicely damped rotation with a center detent. The signature orange volume knob, however, is an endless digital encoder; it spins freely in either direction with no start or end point, which we’ll discuss in great detail later. The power button, which also doubles as the input selector, has a solid click. Overall, it looks and feels like a much more expensive piece of equipment.
A Welcome Surprise: The Internal PSU One of the first things I noticed was the lack of an external power brick. The ZP3 features an internal power supply and uses a standard IEC C5 "Mickey Mouse" power cord. This is a fantastic and welcome upgrade. It cleans up cable clutter significantly and suggests a more robust and thoughtfully engineered power supply section, which is critical for a low-noise component like a preamplifier. For a product in this price bracket, an internal PSU is a premium feature that sets it apart.
Layout and Connectivity The rear panel is logically laid out and generously equipped. You get two single-ended RCA inputs and one balanced XLR input, providing plenty of flexibility for multiple sources. For outputs, it provides both RCA and XLR, which run in parallel, meaning you can’t switch between them; they are both always active. There's also a dedicated mono SUB output. Another pro-level feature is the inclusion of 12V trigger inputs and outputs, which is great for automating your system power-up/down sequence with other compatible gear.
The only truly bizarre design choice is the placement of the switches for the tone control bypass and the High-Pass Filter. They are located on the bottom of the unit. This makes on-the-fly adjustments impossible without lifting the entire preamp. While you might set the bypass switch once and forget it, the HPF is a feature I could see myself wanting to change depending on the music or listening level. It's an inconvenient placement that hints at some of the ergonomic oddities to come.
Core Performance: The Critical Test of Transparency
A preamplifier has one primary job: to manage volume and switch sources without damaging the integrity of the audio signal. It should be a "straight wire with gain," adding nothing and taking nothing away. With my highly revealing speakers, this was the ZP3's most critical test.
The Objective Promise Before I even plugged it in, the ZP3’s official specifications set a very high bar. Fosi claims some truly top-tier numbers on their website:
The Subjective Verdict With the specs setting expectations, I began my listening tests. My methodology was simple: compare my DAC running directly into the Fosi V3 against the same DAC running through the ZP3 (with the tone control bypass switch engaged).
The High-Pass Filter (HPF): A Game Changer for the Main Speakers
The HPF was the main reason I bought the ZP3, and I’m happy to report that this feature is brilliantly executed.
The HPF in Practice The switch on the bottom of the unit offers three settings for the main RCA/XLR outputs: Full-Range (specified as 20Hz-20kHz), an 80Hz high-pass, and a 120Hz high-pass. I tested both filter settings extensively.
Engaging the 80Hz filter was a revelation. On tracks with complex, heavy bass lines, the improvement in my main speakers' performance was not subtle. With the burden of deep bass reproduction lifted, the midrange opened up beautifully. Vocals gained a new level of clarity and presence, and the entire presentation felt less congested and more effortless. Pushing the volume no longer resulted in a sense of strain from the drivers; instead, the music simply got louder, remaining clean and composed. The 120Hz setting was a bit too high for my taste and my specific speakers, creating a noticeable gap in the mid-bass, but it's a valuable option for smaller satellite speakers that simply cannot produce frequencies below that point.
The HPF is not a gimmick. It is a well-implemented, highly effective tool for proper speaker and subwoofer integration. My ears wholeheartedly agree with another user's report that the filters do indeed cut the low frequencies as advertised. For anyone running bookshelf speakers like mine, this feature alone could be worth the price of admission.
Ergonomic Considerations and Design Quirks
For all its sonic purity and the brilliance of its HPF, using the ZP3 on a daily basis reveals some significant ergonomic quirks that potential buyers should be aware of. These issues range from minor inconveniences to more serious operational challenges that stand in contrast to the unit's excellent internal engineering. It’s no wonder that community polls on its performance are so divided, with a significant number of users rating it as "Poor" or "Not terrible" despite its great sound.
Conclusion: A Flawed Gem, but a Gem Nonetheless
The Fosi ZP3 is a fascinating piece of audio equipment, a product of clear contradictions. It is sonically brilliant, with some notable ergonomic quirks. It's a case of thoughtful internal engineering paired with a user interface that requires some getting used to.
Table 1: Fosi ZP3 - A Summary of Findings | Pros | Cons | | :--- | :--- | | Sonically Transparent Performance: Exceptionally low noise and distortion (SNR≥115dB, THD+N≤0.0007%). Adds no audible coloration to the signal. | Unintuitive Volume Control Requires Caution: "Blind" knob with no level indicator requires mindful operation. | | Highly Effective High-Pass Filter: 80Hz and 120Hz settings are genuinely useful for integrating main speakers and improving midrange clarity. | Input Level Mismatch on RCA/XLR: Reported volume jump when switching between RCA and XLR sources. | | Excellent Connectivity & Features: 3 inputs (RCA/XLR), 3 outputs (RCA/XLR/Sub), 12V trigger, and per-input volume memory. | Imprecise, Large Volume Steps: 2-4dB jumps make fine volume adjustment difficult, especially with sensitive speakers. | | Solid Build Quality & Internal PSU: All-metal chassis and an internal power supply feel premium for the price point. | Poor Ergonomics: HPF switch is inconveniently located on the bottom of the unit. | | Convenient Remote Control: Provides basic control over power, volume, mute, and input selection. | |
The Final Verdict for My System So, is the ZP3 staying in my system? For now, yes, with a few caveats. The two things I wanted most—a dead-silent background for my sensitive speakers and an effective HPF—the ZP3 delivers in spades. The sonic improvements are real and significant. However, I've learned to operate it with a certain mindfulness. I have decided to use only the RCA inputs to avoid the level mismatch issue, and I am always careful with the volume knob. It's a compromise, but for my system, the sonic benefits—especially from the HPF—outweigh the drawbacks.
Recommendations for Potential Buyers My recommendation comes with a very strong set of conditions.
Introduction: Setting the Stage – My System and the Search for a Control Center
The Current Setup To understand my evaluation of the ZP3, you first need to understand the system it was dropped into. My setup is built around a philosophy of high-efficiency and high-value performance. The heart of the system is the Fosi V3 power amplifier, a little giant that I’m sure many of you are familiar with. It’s a clean, powerful, and ridiculously good amp for the money. Even on its own, the V3 has a very low noise floor, which made it a good match for my speakers.
The V3 drives a pair of custom high-sensitivity bookshelf speakers, the Audiojam2, designed and built by Alberto Bellino. These speakers are incredibly revealing. With their high sensitivity, they act like a sonic magnifying glass for everything upstream in the audio chain. Any noise, any hiss, any subtle coloration introduced by a component is immediately laid bare. While this makes them a joy for critical listening, it also makes them ruthlessly unforgiving of noisy or subpar electronics. My sources are a Topping DAC for digital files and a turntable running into a separate phono stage for vinyl.
The Problem to Solve My minimalist setup, while sonically pure, had some significant practical limitations.
- Input Juggling: The Fosi V3 has a single RCA input. This meant I was constantly reaching behind my rack to swap cables between my DAC and my phono preamp. It was a daily annoyance that took the joy out of simply deciding what to listen to.
- Volume Control: The V3’s volume knob is small and not remote-controlled. I was often resorting to using the digital volume control on my DAC or computer, which I’ve always been wary of due to the potential for bit-depth reduction and loss of resolution. I craved a proper, high-quality analog-domain volume control with a remote.
- The Bass Management Quest: This was the biggest driver for my search. My Audiojam2 speakers are fantastic, but as bookshelf speakers, they naturally have their limits in deep bass reproduction. Asking them to handle the full frequency spectrum at higher volumes can lead to strain on the drivers and muddy the midrange. I’ve long wanted to integrate a subwoofer, but to do it properly, I needed a way to high-pass the main speakers—that is, to filter out the low bass and send it only to the sub, letting the mains focus on what they do best.
When Fosi announced the ZP3, it seemed like it was designed specifically for me. On paper, it was the perfect solution. It was marketed as a "Versatile Control Hub for Home Audio Systems," which is exactly what I needed. It offered multiple inputs (two RCA, one XLR) to solve my cable-swapping problem, a remote control for volume, and most importantly, an adjustable High-Pass Filter (HPF). The specs were incredible for its $199.99 price point, and the promise of synergy with my existing Fosi V3 was too good to ignore. I placed my order with high hopes that this would be the final piece of my audio puzzle.
Unboxing and Physical Impressions: A Step Up for Fosi
Right out of the box, the ZP3 makes a strong impression. Fosi has been steadily improving its build quality, and this unit feels like a significant step up.
Build Quality and Aesthetics The chassis is a solid, unibody aluminum alloy construction that feels dense and substantial in the hand. Fosi claims this all-metal build provides superior shielding from interference, and based on the heft and seamless construction, I believe it. The main body has the standard Fosi flat black, matte finish, but the side panels are a contrasting shiny black, which is an interesting, if slightly unusual, design choice.
The front panel controls have a satisfying tactile feel. The bass, treble, and balance knobs have a smooth, nicely damped rotation with a center detent. The signature orange volume knob, however, is an endless digital encoder; it spins freely in either direction with no start or end point, which we’ll discuss in great detail later. The power button, which also doubles as the input selector, has a solid click. Overall, it looks and feels like a much more expensive piece of equipment.
A Welcome Surprise: The Internal PSU One of the first things I noticed was the lack of an external power brick. The ZP3 features an internal power supply and uses a standard IEC C5 "Mickey Mouse" power cord. This is a fantastic and welcome upgrade. It cleans up cable clutter significantly and suggests a more robust and thoughtfully engineered power supply section, which is critical for a low-noise component like a preamplifier. For a product in this price bracket, an internal PSU is a premium feature that sets it apart.
Layout and Connectivity The rear panel is logically laid out and generously equipped. You get two single-ended RCA inputs and one balanced XLR input, providing plenty of flexibility for multiple sources. For outputs, it provides both RCA and XLR, which run in parallel, meaning you can’t switch between them; they are both always active. There's also a dedicated mono SUB output. Another pro-level feature is the inclusion of 12V trigger inputs and outputs, which is great for automating your system power-up/down sequence with other compatible gear.
The only truly bizarre design choice is the placement of the switches for the tone control bypass and the High-Pass Filter. They are located on the bottom of the unit. This makes on-the-fly adjustments impossible without lifting the entire preamp. While you might set the bypass switch once and forget it, the HPF is a feature I could see myself wanting to change depending on the music or listening level. It's an inconvenient placement that hints at some of the ergonomic oddities to come.
Core Performance: The Critical Test of Transparency
A preamplifier has one primary job: to manage volume and switch sources without damaging the integrity of the audio signal. It should be a "straight wire with gain," adding nothing and taking nothing away. With my highly revealing speakers, this was the ZP3's most critical test.
The Objective Promise Before I even plugged it in, the ZP3’s official specifications set a very high bar. Fosi claims some truly top-tier numbers on their website:
- Signal-to-Noise Ratio (SNR): SNR≥115dB
- Signal to Noise and Distortion (SINAD): SINAD≥113dB
- Total Harmonic Distortion + Noise (THD+N): ≤0.0007%
- Crosstalk: ≤−130dB
The Subjective Verdict With the specs setting expectations, I began my listening tests. My methodology was simple: compare my DAC running directly into the Fosi V3 against the same DAC running through the ZP3 (with the tone control bypass switch engaged).
- The Noise Floor Test: This was the first and most important test for my system. With high-sensitivity speakers, any residual hiss from electronics is immediately noticeable and incredibly distracting. I connected the ZP3, selected an empty input, and slowly turned the volume knob on the V3 all the way up. Then, I cautiously increased the volume on the ZP3. I put my ear right up to the speaker driver and heard… nothing. Absolute, dead silence. This corroborates another user's report of "no audible hiss". The ZP3's high SNR is not just a number on a page; it translates directly into a black, silent background, even on speakers that are designed to expose any such flaws. This is a massive achievement and a perfect sonic match for a high-efficiency setup.
- Sonic Character: With the noise floor test passed with flying colors, I moved on to music. I spent hours A/B testing, listening for any change in character. The conclusion was clear: the ZP3 is astonishingly transparent. It did not seem to add any coloration or sonic signature of its own. The soundstage remained just as wide and deep. Detail retrieval was identical. The macro and micro-dynamics in my favorite recordings were fully preserved. In bypass mode, the ZP3 is as close to sonically invisible as I could hope for. It successfully performs the function of a preamplifier without imposing its own will on the music.
The High-Pass Filter (HPF): A Game Changer for the Main Speakers
The HPF was the main reason I bought the ZP3, and I’m happy to report that this feature is brilliantly executed.
The HPF in Practice The switch on the bottom of the unit offers three settings for the main RCA/XLR outputs: Full-Range (specified as 20Hz-20kHz), an 80Hz high-pass, and a 120Hz high-pass. I tested both filter settings extensively.
Engaging the 80Hz filter was a revelation. On tracks with complex, heavy bass lines, the improvement in my main speakers' performance was not subtle. With the burden of deep bass reproduction lifted, the midrange opened up beautifully. Vocals gained a new level of clarity and presence, and the entire presentation felt less congested and more effortless. Pushing the volume no longer resulted in a sense of strain from the drivers; instead, the music simply got louder, remaining clean and composed. The 120Hz setting was a bit too high for my taste and my specific speakers, creating a noticeable gap in the mid-bass, but it's a valuable option for smaller satellite speakers that simply cannot produce frequencies below that point.
The HPF is not a gimmick. It is a well-implemented, highly effective tool for proper speaker and subwoofer integration. My ears wholeheartedly agree with another user's report that the filters do indeed cut the low frequencies as advertised. For anyone running bookshelf speakers like mine, this feature alone could be worth the price of admission.
Ergonomic Considerations and Design Quirks
For all its sonic purity and the brilliance of its HPF, using the ZP3 on a daily basis reveals some significant ergonomic quirks that potential buyers should be aware of. These issues range from minor inconveniences to more serious operational challenges that stand in contrast to the unit's excellent internal engineering. It’s no wonder that community polls on its performance are so divided, with a significant number of users rating it as "Poor" or "Not terrible" despite its great sound.
- Quirk 1: The "Blind" Volume Knob Requires Caution: The ZP3's volume knob is a digital encoder that spins endlessly with no physical start or stop point. Critically, there is no display, no ring of LEDs, and no indicator notch on the knob to give you any visual feedback on the current volume level. You are operating completely blind. This lack of a visual indicator becomes a point of concern due to the ZP3's digital "volume memory" feature, which remembers the last-used volume setting for each individual input. The unit powers on at the last digitally set volume level. This requires users to be mindful and develop a habit of checking the volume, especially after the unit has been off or an input has been changed.
- Quirk 2: The Coarse Volume Steps: The problems with volume control don't stop there. The steps between volume adjustments, whether using the knob or the remote, are far too large. I estimated jumps of between 2 and 4dB per click. On my high-sensitivity speakers, a 3dB increase requires a doubling of amplifier power and is a very noticeable jump in volume. This makes finding the right level for quiet, late-night listening an exercise in frustration. One click is too quiet to hear the details, and the very next click is too loud for the room. The inability to make fine-grained adjustments is a major practical limitation that severely impacts the day-to-day user experience.
- Quirk 3: The RCA vs. XLR Level Mismatch: This is a significant operational quirk to be aware of. I have read reports from users on forums like ASR that the output level from the XLR outputs is unexpectedly lower than from the RCA outputs, which is a significant deviation from standard audio engineering practice. For context, standard practice dictates that a balanced XLR signal (+4dBu) should be significantly louder—by nearly 12dB—than a single-ended RCA signal (−10dBV). The ZP3's reported behavior is the direct opposite of this long-established standard. Unfortunately, I was not able to verify this with my own equipment. However, other users have reported that this level mismatch also applies to the inputs. This means that when switching from a source connected via XLR to a source connected via RCA, there can be a sudden and massive jump in volume. This behavior complicates using the ZP3 as a seamless "control hub" for mixed-signal sources. It's highly advisable to turn the volume down before switching inputs to avoid a sudden, jarring change in level.
Conclusion: A Flawed Gem, but a Gem Nonetheless
The Fosi ZP3 is a fascinating piece of audio equipment, a product of clear contradictions. It is sonically brilliant, with some notable ergonomic quirks. It's a case of thoughtful internal engineering paired with a user interface that requires some getting used to.
Table 1: Fosi ZP3 - A Summary of Findings | Pros | Cons | | :--- | :--- | | Sonically Transparent Performance: Exceptionally low noise and distortion (SNR≥115dB, THD+N≤0.0007%). Adds no audible coloration to the signal. | Unintuitive Volume Control Requires Caution: "Blind" knob with no level indicator requires mindful operation. | | Highly Effective High-Pass Filter: 80Hz and 120Hz settings are genuinely useful for integrating main speakers and improving midrange clarity. | Input Level Mismatch on RCA/XLR: Reported volume jump when switching between RCA and XLR sources. | | Excellent Connectivity & Features: 3 inputs (RCA/XLR), 3 outputs (RCA/XLR/Sub), 12V trigger, and per-input volume memory. | Imprecise, Large Volume Steps: 2-4dB jumps make fine volume adjustment difficult, especially with sensitive speakers. | | Solid Build Quality & Internal PSU: All-metal chassis and an internal power supply feel premium for the price point. | Poor Ergonomics: HPF switch is inconveniently located on the bottom of the unit. | | Convenient Remote Control: Provides basic control over power, volume, mute, and input selection. | |
The Final Verdict for My System So, is the ZP3 staying in my system? For now, yes, with a few caveats. The two things I wanted most—a dead-silent background for my sensitive speakers and an effective HPF—the ZP3 delivers in spades. The sonic improvements are real and significant. However, I've learned to operate it with a certain mindfulness. I have decided to use only the RCA inputs to avoid the level mismatch issue, and I am always careful with the volume knob. It's a compromise, but for my system, the sonic benefits—especially from the HPF—outweigh the drawbacks.
Recommendations for Potential Buyers My recommendation comes with a very strong set of conditions.
- Who should consider the ZP3? The "set-and-forget" user. If your plan is to connect all your sources via one input type (e.g., all RCA), you don't switch inputs often, and your primary goal is to use the excellent HPF to relieve your main speakers of deep bass duties, then the ZP3 is a fantastic and transparent bass management tool that is sonically worth far more than its asking price.
- Who should think twice about the ZP3? The "active switcher." If you intend to frequently switch between multiple sources, especially mixing RCA and XLR connections, you should be aware of the operational quirks. The workflow isn't as seamless as a typical preamp, and the need for caution might become frustrating.
