Fosi Audio ZP3 Preamplifier Review

[xanalog]

…and @JSmith is back at it! Thanks for the internal pics.

Yeah!
We don't need no stinkin' AIs for his valuable contributions.

 

[2fatpugs]

Hi, I am planning on using the ZP3 purely as a high pass filter for my XLR connection. Anyone know what the slope of the HPF is?

 

[totti1965]

Hi, I am planning on using the ZP3 purely as a high pass filter for my XLR connection. Anyone know what the slope of the HPF is?

Just take a look at @amirm‘s measurements (80 Hz Filter)
At 100 Hz we are exactly at -2.2 dB
At 70 Hz we are exactly at -4.8 dB
So 2.6 dB attenuation per half of an octave.
5.2 dB/octave
Roughly a 6 dB per octave Filter!
This is quite o.k.

In a perfect world it would be -6 dB @ 80 Hz and switchable slope (6 dB / 12 dB / 18 dB / 24 dB / 30 dB / 36 dB)

 

[2fatpugs]

I found a fix for the volume knob

 

[iLoveCats]

I found a fix for the volume knob

 

[totti1965]

I found a fix for the volume knob

...unless the cleaning lady wants to play a nasty trick on you...

 

[Joe Smith]

I found a fix for the volume knob

Yeah, that's just perfect. So, no problem... We all want our kit to look like that, right?

 

[totti1965]

@iLoveCats: I need a bit to understand your comment.... You wanted to say: "without words" so you wrote simply not a single word
Perhaps this musical cat does use the Fosi Audio ZP 3 in its spare time (If the music starts a little louder than usual due to the impossible volume control... At least this cat here doesn't seem to mind...)

 

[somebodyelse]

I found a fix for the volume knob

I don't see how that's a fix. There's still no indication of the volume, and it can still be changed with the remote, or potentially by a firmware bug for those that worry about that scenario.

 

[Boredcarrot]

I don't see how that's a fix. There's still no indication of the volume, and it can still be changed with the remote, or potentially by a firmware bug for those that worry about that scenario.

I believe it was a joke.

 

[iLoveCats]

@iLoveCats: I need a bit to understand your comment.... You wanted to say: "without words" so you wrote simply not a single word
Perhaps this musical cat does use the Fosi Audio ZP 3 in its spare time (If the music starts a little louder than usual due to the impossible volume control... At least this cat here doesn't seem to mind...)

hahaha I replied with just laughing emoji's from my phone which did not get posted.

 

[Billy Budapest]

I had to rate the ZP3 “poor.” The lack of a volume indicator for its digital volume control is its fatal flaw. This is a recipe for destroying amps, speakers, and headphones, and potentially inducing hearing loss.

This flaw could be easily fixed with a minor redesign. Either incorporate a tiny display to show volume a la the Parasound HINT or Sony TA-A1ES, or introduce a knob that does not spin freely but rather, its position is sensed to control the volume chip.

 

[DavidEdwinAston]

I had to rate the ZP3 “poor.” The lack of a volume indicator for its digital volume control is its fatal flaw. This is a recipe for destroying amps, speakers, and headphones, and potentially inducing hearing loss.

This flaw could be easily fixed with a minor redesign. Either incorporate a tiny display to show volume a la the Parasound HINT or Sony TA-A1ES, or introduce a knob that does not spin freely but rather, its position is sensed to control the volume chip.

My Ruark powered speakers have an "infinity" volume , like this preamp. I always rotate it anti clockwise, like a fiend, before introducing music! To be fair, that music is coming from my phone where I can,of course vary the volume in advance!
However, perhaps the fiendish rotating would ensure safety?

 

[Billy Budapest]

My Ruark powered speakers have an "infinity" volume , like this preamp. I always rotate it anti clockwise, like a fiend, before introducing music! To be fair, that music is coming from my phone where I can,of course vary the volume in advance!
However, perhaps the fiendish rotating would ensure safety?

It probably would, but I am sure a lot of people would forget to do that.

 

[Progronom]

Hello!
I have the following problem. Connection: Player -> RCA Fosi ZP3 -> RCA Power Amplifier -> Acoustic Speakers.
With "Bypass-On" (tone block disabled), the speakers are silent when paused. I put my ear right next to the tweeter and it's completely silent.
With "Bypass-Off" (tone block enabled), there's a loud hissing noise in the speakers. It can be heard from 0.5 meters away from the tweeter.

1. The level of the hissing noise doesn't depend on the volume setting. In Position 0, the hissing noise doesn't stop.

2. The selected input doesn't matter. Even if I disconnect the RCA cable from the ZP3, the hissing noise doesn't stop. All three inputs have this noise.

3. I replaced the power amplifier. The cable between the RCA Fosi ZP3 and the RCA Power Amplifier was also replaced. The hissing noise remains.

Is this a defect?

I have a Fosi P4. It doesn't have this noise. In any "Bypass" position, there's absolute silence.

 

[PC Audio Lover]

Hello!
I have the following problem. Connection: Player -> RCA Fosi ZP3 -> RCA Power Amplifier -> Acoustic Speakers.
With "Bypass-On" (tone block disabled), the speakers are silent when paused. I put my ear right next to the tweeter and it's completely silent.
With "Bypass-Off" (tone block enabled), there's a loud hissing noise in the speakers. It can be heard from 0.5 meters away from the tweeter.

1. The level of the hissing noise doesn't depend on the volume setting. In Position 0, the hissing noise doesn't stop.

2. The selected input doesn't matter. Even if I disconnect the RCA cable from the ZP3, the hissing noise doesn't stop. All three inputs have this noise.

3. I replaced the power amplifier. The cable between the RCA Fosi ZP3 and the RCA Power Amplifier was also replaced. The hissing noise remains.

Is this a defect?

I have a Fosi P4. It doesn't have this noise. In any "Bypass" position, there's absolute silence.

I have a ZP3 and purchased it for the high pass filter. (Felt like I waited FOREVER for a unit like this w/ a HPF.) I have recently noticed the same issue: a hiss from my tweeters, the volume of which isn't affected at all by the pre-amp's volume setting. It only happens with Bypass is turned off (which, UNFORTUNATELY, you need to do when using the HPF, as the Bypass functionality not only bypasses the Tone Controls but also the HPF. STUPID move Fosi.) I'm seriously pissed and wish I never would have purchased this thing. I'm past the return window.

Oh, but it's DEAD silent in Bypass mode, so if you purchased this not really intending to use a lot of it's functionality, then you have a nice quality unit.

 

[PC Audio Lover]

UPDATE WITH ALL THE DETAILS:

The ZP3 has a hiss. (False advertising on specs?)

If you plan to use the HPF or tone controls on the ZP3, please note: Both the tone controls and the HPF are handled by an EQ chip, and with the EQ chip in the circuit path it introduces a low volume hiss you'll hear from your tweeters (like white noise.) The volume and character of the hiss is completely independent of the input or volume setting on your unit (or any other setting like HPF or tone control settings) - even having the volume control all the way down to 0 will not make the hiss go away. Likewise, cranking the volume knob up will not affect the volume of the hiss. If you turn on Bypass mode, the hiss goes away and the unit is dead quiet (thus meeting the specs Fosi has actually advertised!) BUT if you don't turn on the Bypass because you want to use the High Pass Filter or the tone controls, then you'll have to live with the hiss.

I've owned the ZP3 since release and have had a lot of communication with Fosi support both pre and post purchase. I was very frustrated to discover this. I asked Fosi before purchasing if the HPF was purely analog and they said yes, which apparently is not correct. I also asked them before purchasing what the Bypass mode bypassed and they indicated only the Tone Controls, which is also not true: it also bypasses the HPF. I think many people purchased this unit for the unique functionality like the HPF, so it's such a shame to discover you'll need to use a noisy preamp if you want this functionality. That and the "no volume indicator" issue really screwed up what would otherwise be a killer product. Such a shame.

 

[CJH]

UPDATE WITH ALL THE DETAILS:

The ZP3 has a hiss. (False advertising on specs?)

If you plan to use the HPF or tone controls on the ZP3, please note: Both the tone controls and the HPF are handled by an EQ chip, and with the EQ chip in the circuit path it introduces a low volume hiss you'll hear from your tweeters (like white noise.) The volume and character of the hiss is completely independent of the input or volume setting on your unit (or any other setting like HPF or tone control settings) - even having the volume control all the way down to 0 will not make the hiss go away. Likewise, cranking the volume knob up will not affect the volume of the hiss. If you turn on Bypass mode, the hiss goes away and the unit is dead quiet (thus meeting the specs Fosi has actually advertised!) BUT if you don't turn on the Bypass because you want to use the High Pass Filter or the tone controls, then you'll have to live with the hiss.

I've owned the ZP3 since release and have had a lot of communication with Fosi support both pre and post purchase. I was very frustrated to discover this. I asked Fosi before purchasing if the HPF was purely analog and they said yes, which apparently is not correct. I also asked them before purchasing what the Bypass mode bypassed and they indicated only the Tone Controls, which is also not true: it also bypasses the HPF. I think many people purchased this unit for the unique functionality like the HPF, so it's such a shame to discover you'll need to use a noisy preamp if you want this functionality. That and the "no volume indicator" issue really screwed up what would otherwise be a killer product. Such a shame.

I hope Fosi fixes this or someone else build a similarly functioning unit that works correctly.
CJH

 

[2fatpugs]

UPDATE WITH ALL THE DETAILS:

The ZP3 has a hiss. (False advertising on specs?)

If you plan to use the HPF or tone controls on the ZP3, please note: Both the tone controls and the HPF are handled by an EQ chip, and with the EQ chip in the circuit path it introduces a low volume hiss you'll hear from your tweeters (like white noise.) The volume and character of the hiss is completely independent of the input or volume setting on your unit (or any other setting like HPF or tone control settings) - even having the volume control all the way down to 0 will not make the hiss go away. Likewise, cranking the volume knob up will not affect the volume of the hiss. If you turn on Bypass mode, the hiss goes away and the unit is dead quiet (thus meeting the specs Fosi has actually advertised!) BUT if you don't turn on the Bypass because you want to use the High Pass Filter or the tone controls, then you'll have to live with the hiss.

I've owned the ZP3 since release and have had a lot of communication with Fosi support both pre and post purchase. I was very frustrated to discover this. I asked Fosi before purchasing if the HPF was purely analog and they said yes, which apparently is not correct. I also asked them before purchasing what the Bypass mode bypassed and they indicated only the Tone Controls, which is also not true: it also bypasses the HPF. I think many people purchased this unit for the unique functionality like the HPF, so it's such a shame to discover you'll need to use a noisy preamp if you want this functionality. That and the "no volume indicator" issue really screwed up what would otherwise be a killer product. Such a shame.

I think you might have a bad unit. I just tested my HPF and these is absolutely no hiss, even at reference level. Also bypassing the tone control does not by pass the HPF. I am running my Martin Logan CLS at 120hz and it is definitely working.

 

[PC Audio Lover]

I think you might have a bad unit. I just tested my HPF and these is absolutely no hiss, even at reference level. Also bypassing the tone control does not by pass the HPF. I am running my Martin Logan CLS at 120hz and it is definitely working.

1. I literally confirmed with Fosi support the hiss is part of the product, and getting a new unit won't fix the problem. Plus, at this point I've seen at least 3 other people on the internet report this precise issue with the same characteristics. Do me a favor: make sure your room is quiet, turn your Bypass switch to "OFF", and put your ear up to your tweeter and see if you notice it. Let us know here. I'm curious.
2. Switching Bypass mode to on (which is the label "BYPASS" on the switch) does, in fact, bypass the HPF. I've tested it many times. You can tell clearly with your ears, but I also have a UMIK-1 to confirm. If Bypass is off (the label "OFF"), switching the HPF switch settings has a noticeable difference on the mains' bass. If Bypass is on, the HPF settings makes no difference at all. Fosi support also confirmed this is how the Bypass switch works.

I'm curious... when did you purchase your ZP3 2fatpugs? And from where? Did you make any alterations to the op-amps or anything else?