Fosi Audio V3 Amplifier Review

[NoMoFoNo]

Looks like need a really good stereo aux cable (no oxygen copper - double shielded low noise high grade). Connected a (3.5 mm to rca) high grade low noise cable with gold plated connectors that I had to the pre out, almost no noise now. Good Cables are expensive. Setting up c hifi is rabbit hole.

Fixed it for you.

 

[antcollinet]

Looks like need a really good stereo aux cable (no oxygen copper - double shielded low noise high grade). Connected a (3.5 mm to rca) high grade low noise cable with gold plated connectors that I had to the pre out, almost no noise now. Good Cables are expensive. Setting up chifi is rabbit hole

It doesn't look like that at all. This is an output. No way should plugging something into it influence the sound from the amp, regardless of the cable.

And if you are spending money on expensive cables you are wasteing your money. Good cables don't need to be expensive. Many expensive cables are not good. Need for OFC is a myth - though that also doesn't cost much.

Oh, And we are asked not to use the "chifi" term here.

Let's Avoid the Term Chi-Fi

I often see the use of the term "Chi Fi" to describe audio products from China. I see the intention and don't think anyone is trying to be racist and what have you. Still, I like us to show the highest respect to products from around the world. As avid readers of this forum know...

www.audiosciencereview.com

 

[antcollinet]

If I connect 3.5 mm male to male aux cabel to pre out and max out the volume on amp I get distortion or noise in speaker without any music...80% volume , no noise...

My setup is fosi audio p1 as pre amp, fosi Audio v3 as power amp, mb 42x speakers and I connect preamp to smartphone using rca to 3.5mm jack.

If I connect preout cabel to subwoofer amp still distortion exists. If I don't connect pre out to sub woofer amp distortion exists. If I remove preout cabel from fosi audio v3 distortion goes away. I changed few cables... Used LF 3.5mm aux cable still distortion is there...

As promised - just checked.

If I only plug in a cable and turn up the volume to full, there is no noise. If I touch the end of the cable then there is some 50Hz hum. This suggests feedback from the output back to the preout input (between volume control and power amp).

Not ideal. If you are getting noise with no connection to the cable other than the amp (you are not touching it), it could be a significant source of radiated noise in your room and the cable is acting as an antenna. Or perhaps another coupling mechanism is at play (eg if you have a ground loop in your system)

 

[GGroch]

It doesn't look like that at all. This is an output. No way should plugging something into it influence the sound from the amp, regardless of the cable.

On the V3, at least the original release version, the "Pre-Out" is just a direct split from the line in. It is not isolated or volume controlled, it will work as an input.

 

[antcollinet]

On the V3, at least the original release version, the "Pre-Out" is just a direct split from the line in. It is not isolated or volume controlled, it will work as an input.

Ah - that explains it. Not a pre-out at all then.

 

[375HP2482]

It's unfortunate that Aiyima/Fosi chose to label the alternate input connector as "Pre Out," which implies (incorrectly) that there is an active discrete amplifier (opamp) powering it.

In reality, the RCA and 3.5mm jacks are simply there to offer alternative (parallel) input connections to the unit.

 

[375HP2482]

If I only plug in a cable and turn up the volume to full, there is no noise. If I touch the end of the cable then there is some 50Hz hum. This suggests feedback from the output back to the preout input (between volume control and power amp).

More likely it is an indication that one of the cable ends is effectively unterminated (high impedance/open circuit). In that state any stray fields will, through induction and/or antenna action, inject the small amount of current required to trigger that noise.

Just about any electric guitar player is familiar with the loud AC line hum/buzz when the cord connected to their guitar amplifier is unplugged from the guitar, or goes bad. Similarly, this type of noise can also arise with long runs to amplifiers that are powered off.

 

[antcollinet]

More likely it is an indication that one of the cable ends is effectively unterminated (high impedance/open circuit). In that state any stray fields will, through induction and/or antenna action, inject the small amount of current required to trigger that noise.

Just about any electric guitar player is familiar with the loud AC line hum/buzz when the cord connected to their guitar amplifier is unplugged from the guitar, or goes bad. Similarly, this type of noise can also arise with long runs to amplifiers that are powered off.

Typical audio amp input impedance is 47K. They are not supposed to be terminated.

 

[Toku]

There have been several reports of trouble with ASR's 3.5mm jack in the past. In most cases, the cause was insufficient insertion of the 3.5mm plug.
Depending on the jack, it might be a little tight, and in that case, it wouldn't be inserted properly, causing trouble. The jack on my Fosi V3 also requires some force to insert.
I would suggest that you double check that the plug is inserted correctly.

 

[DavidMcRoy]

They're sending me one to test, but I really doubt that it would be a step backward from the original A07, still a perfectly good little amp. The only quibble I've heard thus far is that the 50V capacitors are not well suited for a 48v power brick. I think they are sending mine with a 30 or 32v power brick. The old A07 got plenty loud with that size of power supply. I do agree that the Fosi V3 seems to be a bit better thought out in terms of component values, cooling etc.

I ordered an A07 Max with a 36 VDC supply. It just arrived. Haven't tried it yet. I suspect it'll subjectively sound identical to the original A07 and to the Fosi V3 to me. I needed another amp so I thought I'd get a Max for grins.

 

[GoaBhau]

As promised - just checked.

If I only plug in a cable and turn up the volume to full, there is no noise. If I touch the end of the cable then there is some 50Hz hum. This suggests feedback from the output back to the preout input (between volume control and power amp).

Not ideal. If you are getting noise with no connection to the cable other than the amp (you are not touching it), it could be a significant source of radiated noise in your room and the cable is acting as an antenna. Or perhaps another coupling mechanism is at play (eg if you have a ground loop in your system)

Thanks for testing. what kind of cabel was used? Can you please attach an image of it. All the replies point towards induction, I am not understanding ground loop problem. I'll check about it.

Edit:

Below is my current fix, aluminium wrapped cable. I think main problem is something to with ground or induction...

 

[GoaBhau]

If I connect 3.5 mm male to male aux cabel to pre out and max out the volume on amp I get distortion or noise in speaker without any music...80% volume , no noise...

My setup is fosi audio p1 as pre amp, fosi Audio v3 as power amp, mb 42x speakers and I connect preamp to smartphone using rca to 3.5mm jack.

If I connect preout cabel to subwoofer amp still distortion exists. If I don't connect pre out to sub woofer amp distortion exists. If I remove preout cabel from fosi audio v3 distortion goes away. I changed few cables... Used LF 3.5mm aux cable still distortion is there...

This is final make shift fix from my end, YES @antcollinet it is a ground issue, Thank you for pointing it out, my OCD can rest now. My fosi audio v3 cabinet was leaking current like my MacBook (felt buzz on moving fingers when I touched the case) as it doesn't have ground connection. I connected 3.5mm ground to electric switch board panel ground, now there is no current leak in the case. Also after doing this noise is ABSOLUTELY ZERO.

What could be good actual fix for this or this is it?

 

[Fox _ Mulder]

Thanks for testing. what kind of cabel was used? Can you please attach an image of it. All the replies point towards induction, I am not understanding ground loop problem. I'll check about it.

Edit:

Below is my current fix, aluminium wrapped cable. I think main problem is something to with ground or induction...

Are you using the tube as a DAC and preamp?

 

[GoaBhau]

Are you using the tube as a DAC and preamp?

Using tube p1 as volume control, preamp and eq, fosi v3 is at full volume now, there is no dac in P1, my smartphone has a decent dac.

 

[antcollinet]

What could be good actual fix for this or this is it?

If you can do a sketch of your system - including all components, how they are connected together, and how they are earthed (if they are) Including your temporary earth for the FOSI, I'll have a think.

Photo of hand drawn sketch is fine.

 

[johnsogr]

So, I got this from Prime Day say in the UK for £49 with a 32V power supply. I wonder if it would be a decent option with the Revel M16 speakers I got.
But, sub integration would be a pita, isn't it?

BTW, which pre-amp/streamer you guys are using with it?
I would like to know if there is any cheap but good streamer with a sub-out and volume control to use alongside the Fosi V3 (if indeed the amp is good enough for the speakers).

I actually paired my Fosi V3 with the Revel m16's and I really like it (my original plan was the Revels with a vintage Marantz 2220b, but that amp has a ton of distortion I'm trying to figure out). That said, this is my first foray into "hifi" and stereo setup at all so I have a lot to learn. Right now I stream from a Wiim pro into a Schiit Modi DAC then into the V3.

I'd like to add a phono and a sub at some point (phono first), here's what I'm looking at:

1. Fluance RT 85
2. Phono preamp either Fosi Box X2 or Schiit Mani (any suggestions)
3. Preamp Schiit Saga S or Lyr+ (I'm open to any suggestions)

If/when I use a preamp, do I set the V3 to max volume and use the preamp as the volume control? Or do I set the V3 somewhere else on the dial (I have the 48V 5A power supply).

Thanks everyone, and I appreciate your patience, again, so much to learn.

 

[mike70]

I actually paired my Fosi V3 with the Revel m16's and I really like it (my original plan was the Revels with a vintage Marantz 2220b, but that amp has a ton of distortion I'm trying to figure out). That said, this is my first foray into "hifi" and stereo setup at all so I have a lot to learn. Right now I stream from a Wiim pro into a Schiit Modi DAC then into the V3.

I'd like to add a phono and a sub at some point (phono first), here's what I'm looking at:

1. Fluance RT 85
2. Phono preamp either Fosi Box X2 or Schiit Mani (any suggestions)
3. Preamp Schiit Saga S or Lyr+ (I'm open to any suggestions)

If/when I use a preamp, do I set the V3 to max volume and use the preamp as the volume control? Or do I set the V3 somewhere else on the dial (I have the 48V 5A power supply).

Thanks everyone, and I appreciate your patience, again, so much to learn.

The Marantz maybe have more distortion than the Fosi ... but surely you won't hear it in normal circunstances (big room / high SPL can be a problem for both, but i hope isn't the case). Decision can be maded based on price tag / looks / whatever ... but SINAD above 75dB generally turns amplifiers in the blind test "everything's the same" category.
Higher SINADs shows better engineering and is a facet to check it out, but not necessarily is a real ("in room") SQ direct improvement.
Obviously, if you see an Accuphase with 5k price tag with the same SINAD than a 1k price tag ... maybe you have an easy decision ("audiophiles" will take the Accuphase anyway ). Only my opinion, of course.

As a "rule of the thumb", to use an amp (with volume) with an external preamp, generally we left the amp at max volume (no resistance) and use the preamp to control the volume.

 

[NoMoFoNo]

The Marantz maybe have more distortion than the Fosi ... but surely you won't hear it in normal circunstances (big room / high SPL can be a problem for both, but i hope isn't the case). Decision can be maded based on price tag / looks / whatever ... but SINAD above 75dB generally turns amplifiers in the blind test "everything's the same" category.
Higher SINADs shows better engineering and is a facet to check it out, but not necessarily is a real ("in room") SQ direct improvement.
Obviously, if you see an Accuphase with 5k price tag with the same SINAD than a 1k price tag ... maybe you have an easy decision ("audiophiles" will take the Accuphase anyway ). Only my opinion, of course.

As a "rule of the thumb", to use an amp (with volume) with an external preamp, generally we left the amp at max volume (no resistance) and use the preamp to control the volume.

Great call. There are exceptions, as in my case where the preamp/line-stage produces high gain. The manual for my preamp notes that best range for volume control is 10-to-2 on the dial, and to set the amplifier gain controls (if possible) to be able to use that range on the preamp itself. For me then, the V3 volume ends up just under 12 on the dial. If I maxed out the volume on the V3, I'd be way loud by turning the preamp volume to 7 or 8 on the dial. Just food for thought for those who will use the V3 with a preamp.

 

[mike70]

Great call. There are exceptions, as in my case where the preamp/line-stage produces high gain. The manual for my preamp notes that best range for volume control is 10-to-2 on the dial, and to set the amplifier gain controls (if possible) to be able to use that range on the preamp itself. For me then, the V3 volume ends up just under 12 on the dial. If I maxed out the volume on the V3, I'd be way loud by turning the preamp volume to 7 or 8 on the dial. Just food for thought for those who will use the V3 with a preamp.

well, yes, some amps have different gain settings to solve that problems.

 

[NoMoFoNo]

well, yes, some amps have different gain settings to solve that problems

Yep, was just pointing out that it's not necessarily as simple as pegging the volume on the V3 (or any amp with volume control) when using a pre in front of it.