Fosi Audio V3 Mono Amplifier Review

[somebodyelse]

Fosi amps will be out of phase with the other amps.

Depends on the other amps. Some are inverting, others non-inverting.

 

[Bleib]

I asked Fosi about it, I have an order for 2 of them
"Hello There,
We have thoroughly tested our product at the factory before shipping, ensuring there won't be any issues. If needed, we can provide a video for you. Shall we proceed with the shipment as usual?
--
[Fosi Audio]"

 

[Sokel]

Maybe I'm wrong but I don't think there is any intrinsic standard for whether amps are phase inverting or not so I would expect to have to check phase (by listening) whenever I had disparate amps in a system.

I think it's to do with amp design, each stage in an amp is generally going to invert phase so if mixing even and odd amplification stage designs you'll likely have to switch terminals for one of them. It isn't a correct or incorrect sort of thing.

Also - using the balanced inputs seems to have reversed the problem in the example given above - that could make sense as using RCA inputs goes through an extra opamp to convert to balanced so possibly there is the extra amplification stage flipping polarity. (That's just a guess, I'm not at all familiar with opamp internals and whether they count as a single or multiple stage device).

There is (kind of) a standard and that is to output the same as input.
But regardless,even if it was an inverting amp like a few others in the past it should be on both inputs or (the proper way) none of them.

The least they should do is warn about it,imagine people running manual EQ down low filling dips (wrong,but they do) having the exact opposite effect as it's evident for example at @Miser_Audioman 's measurement.

I asked Fosi about it, I have an order for 2 of them
"Hello There,
We have thoroughly tested our product at the factory before shipping, ensuring there won't be any issues. If needed, we can provide a video for you. Shall we proceed with the shipment as usual?
--
[Fosi Audio]"

I wonder if they even know what you asked,that's not an answer by an educated engineer,probably typical PR stuff.

 

[Pecottye]

I found the phasing on the v3s to be reversed from standard, see owners thread

Thank you for this remark! I now understand why the bass was thinner than with the Edge X-300 in combination with my sub. I just inverted the speakerwires and got it back again .

 

[activewire]

It is difficult to get my head around this type of performance is such a small and inexpensive package. I have been looking to add an amplifier to my Onkyo RZ50 to drive my front speakers-ML Vistas (4 Ohm). I have no complaints with the RZ50, but the V3 Mono Blocks appear to perform better on the bench. I would be interested if people think that there would be a noticeable difference (Better or Worse) in sound quality.

I also have the RZ50 and am now building a 9 channel amp (using tpa3255 just like Fosi V3 mono see my DIY thread) for same reasons you cited.

 

[Freezak]

I have one more question - do i actually gain anything by buying two power supplies, be it 48V/5A or 48V/10A instead of one 48V/10A (+ power filter and splitter) for driving two Fosi V3 monos? they're gonna be connected to SMSL C200 or D6s and bookshelf speakers Elac DBR62. Any help would be appreciated as i have ordered the 2x Fosi V3 mono + 1x 48V/10A power filter set - i guess i could still exchange it to 2x Fosi V3 mono + 2x 48/5V as it's the same price either way - thank you!

 

[Megaken]

Indeed, but I bought the dual version on amz.es for 40eur!

Later I've found other brand that sells a similar 80mm duals just for 14 eur...

This is not a fan - it doesn't actually cool anything down. Put your hand to it - it doesn't blow. It's an exhaust.

This one does https://acinfinity.com/component-co...nd-av-quiet-cabinet-cooling-fan-system-4-inch

 

[gelo_mc]

There is (kind of) a standard and that is to output the same as input.
But regardless,even if it was an inverting amp like a few others in the past it should be on both inputs or (the proper way) none of them.

The least they should do is warn about it,imagine people running manual EQ down low filling dips (wrong,but they do) having the exact opposite effect as it's evident for example at @Miser_Audioman 's measurement.



I wonder if they even know what you asked,that's not an answer by an educated engineer,probably typical PR stuff.

I know it is trivial just to switch the rca cables if you are aware of the issue but the problem is not all people go to forums about a product. Even if they do, can be easily buried in a long thread like this.

This is quite easy for fosi to rectify. Just swap the labels of the terminal or switch the wiring internally. They haven't acknowledge the problem though.

 

[Bleib]

OK, Fosi has now been directed to this topic through email, to the first post where it was brought up

 

[Sokel]

I know it is trivial just to switch the rca cables if you are aware of the issue but the problem is not all people go to forums about a product. Even if they do, can be easily buried in a long thread like this.

This is quite easy for fosi to rectify. Just swap the labels of the terminal or switch the wiring internally. They haven't acknowledge the problem though.

Switch the cables how?Speaker cables you mean?
Yes,but you'll have to reverse them any time you change the input.

Can't be labeled too as any labeling would be true only for the one of the two inputs.
Labeled as a warning,sure.

 

[Borland]

My V3s have also arrived
But they get very hot and I wonder when hot is too hot....

I have now ordered an infrared thermometer.

Edit:
Do they perhaps get so hot because I use 10A power supply units? Is it better to use a splitter cable and only one power supply?

 

[gelo_mc]

Switch the cables how?Speaker cables you mean?
Yes,but you'll have to reverse them any time you change the input.

Can't be labeled too as any labeling would be true only for the one of the two inputs.
Labeled as a

Yep i mean speaker cables. Got your point it will only be valid for one input and always wrong to the other

 

[gelo_mc]

My V3s have also arrived
But they get very hot and I wonder when hot is too hot....

I have now ordered an infrared thermometer.

Edit:
Do they perhaps get so hot because I use 10A power supply units? Is it better to use a splitter cable and only one power supply?

Probably yes. I have a fosi BT20A with 32V 5A and never get noticeably hot. Measured 32 Celsius on my thermometer.

 

[avdoc]

My V3s have also arrived
But they get very hot and I wonder when hot is too hot....

I have now ordered an infrared thermometer.

Edit:
Do they perhaps get so hot because I use 10A power supply units? Is it better to use a splitter cable and only one power supply?

I use one of these fans below each of my amps and they stay cool: https://www.amazon.com/dp/B0928KWHZF?psc=1&ref=product_details

 

[audioguy272727]

My V3s have also arrived
But they get very hot and I wonder when hot is too hot....

I have now ordered an infrared thermometer.

Edit:
Do they perhaps get so hot because I use 10A power supply units? Is it better to use a splitter cable and only one power supply?

Mine arrived yesterday and are also hot - and they seem hotter than my PA7 - warming them up now and will use my trusty COVID surface temperature thermometer. I will compare to PA7 and share findings.

 

[Miser_Audioman]

Fosi reached out to me, I’ll talk to them but reversing the speaker cables was fine for me. By the way, i fed these Shostakovich 11, Bychkov conducting. Extremely dynamic and challenging recording. Just beautiful frankly, they really held up (i have efficient speakers, high pass, sub so not a challenging set up power wise for any amp).

 

[Miser_Audioman]

If you want me to convey a suggestion to them on this issue, lmk. To me, swapping the plastic color coders seems like a good fix moving forward. Current units?

 

[gwing]

If you want me to convey a suggestion to them on this issue, lmk. To me, swapping the plastic color coders seems like a good fix moving forward. Current units?

How is that going to help if it is opposite for XLR and RCA inputs?

 

[Deleted member 72219]

If you want me to convey a suggestion to them on this issue, lmk. To me, swapping the plastic color coders seems like a good fix moving forward. Current units?

If you implement this, “fix,” for RCA users, it becomes wrong for XLR users.

-Ed

 

[gwing]

Probably yes. I have a fosi BT20A with 32V 5A and never get noticeably hot. Measured 32 Celsius on my thermometer.

Probably not

The 5A and 10A power supplies are the same voltage so the idle/standby current and heat output would be identical for any of the power supply configurations.