Fosi Audio V3 Mono Amplifier Review

[burkm]

There's been at least one report of one unit being hotter than the other but I didn't see any follow up. The cooler one likely did not have paste. Open it. But you better have paste on hand to replace it from opening it. Mine are very warm and I don't suspect missing paste.

But how do You change or add thermal paste ? There has only been one person, who answered this, but I like to get more alternative answers to the "How to..." procedure.

 

[Rgv250]

Yes - inverting the output in the Flex will do the same as swapping the speaker connections. Also your SVS sub will almost certainly have a phase switch or knob because it's a normal thing to check when setting up a sub, probably described in the SVS manual. If you've got the frequency and slope of the sub crossover correct then incorrect phase will show as a big dip at the crossover frequency, while correct phase would have a flat response, or at least flatter. You might be unlucky and have a room response null at crossover frequency, in which case it may be hard to spot the difference.

Oh, so I get a big dip when inverting phase, but not at the frequency I chose for crossover. I am new to using a sub and miniDsp etc so followed miniDsp instructions on setting up my Flex. I was a bit confused as to where they got their crossover frequency from in the online guide. I choose 85hz and to be honest it does drop on inversion but only by a few dB. But, at 103hz there’s a massive sharp drop on inversion. So, does that mean I should use 103hz as crossover and that the SVS sub is actually in phase with the V3 monos? All interesting stuff even if I don’t fully understand

 

[vuittion]

Mines all packed up ready to ship back to Amazon UK.

Things I dont like.

1) I dont like the nasally glass like tone/sound of the amps.

2) ) Poor musicality/fatiguing

3) They run far to hot considering they are class d, I thought they where suppossed to run cooler.

4) The wiring inside looks a complete mess.

5) The inverted polarity fu#k up.

6) This is about the 6th class d amp i've purchased and they all sound shite.

7) Even the excellent measurements couldn't save it.

8) Back out of storage comes my lovely Arcam FMJ A39.
Lets make sweet music, Oh, how I've missed you.

9) Bye bye class d.

 

[Doodski]

This signals to me, that the thermal paste should be applied to the chip or to be exact, to its alu heatsink, and not to the bottom of the alu casing marked by the two screw positions.
Should the thermal paste be - thinly - covering the chips complete heat sink ?

That depends on the clearances when removing and reinstalling the PCB. You only need to coat one side as in either the chip or the heatsink.

The needed slide-in of the 4-layer PCB with its attached components does not (at least partially) remove or damage the layer of the rather thin thermal paste covering the alu heatsink during its movement ?

You will need decide if the clearance is enough. I do not have the unit in hand.

 

[burkm]

Mines all packed up ready to ship back to Amazon UK. Things I dont like.

1) I dont like the nasally glass like tone/sound of the amps.

2) They run far to hot considering they are class d, I thought they where suppossed to run cooler.

3) The wiring inside looks a complete mess.

4) The inverted polarity fu#k up.

5) This is about the 6th class d amp i've purchased and they all sound shite.

6) Back out of storage comes my lovely Arcam FMJ A39.
Lets make sweet music. Bye bye class d.

My NCore 400 stereo amps run quite hot too (can't touch the casing), thus I installed fans above it and increased some of the top case holes to get more (hot) air circulating...
Individual preferences for specific audio styles are widly (and subjectivly) devergent and determined by ones taste, thus some will like class D amps other won't for whatever reasons and most don't care about the class type of theyr amps. At least for me it's thus a "non event..."

 

[Doodski]

My NCore 400 stereo amps run quite hot (casing), thus I installed fans to it and increased some of the case holes to get more air exchange...

Heatsinking to a thin metal case is not the best method of dissipating the heat. So some heat is expected when touching the case.

 

[burkm]

Heatsinking to a thin metal case is not the best method of dissipating the heat. So some heat is expected when touching the case.

But it reduced the heat to the touch by quite a margin ...

 

[Doodski]

But it reduced the heat to the touch by quite a margin ...

You applied the thermal paste now?

 

[burkm]

No, not yet. I will tackle that tomorrow and will see during that action, if the polarity of the amps I got in diverse deliveries, have been changed already or I will - probably - attach a sticker to the rear plate if I don't switch the polarity of the speaker cables myself.

 

[rvsixer]

Mines all packed up ready to ship back to Amazon UK. Things I dont like.

1) I dont like the nasally glass like tone/sound of the amps.

2) ) Poor musicality/fatiguing

3) They run far to hot considering they are class d, I thought they where suppossed to run cooler.

4) The wiring inside looks a complete mess.

5) The inverted polarity fu#k up.

6) This is about the 6th class d amp i've purchased and they all sound shite.

7) Even the excellent measurements couldn't save it.

8) Back out of storage comes my lovely Arcam FMJ A39.
Lets make sweet music, Oh, how I've missed you.

9) Bye bye class d.

Blaming all the sound deficiencies on class D, when in actuality they are caused by entirely different things. Now the launch, qc, and reliability issues; those are real and the reason I am likely going to spend $295 USD more for a stereo Hypex over dual Fosi mono's.

 

[Lux_ury]

Quick test on 4ohms speakers with temperatures.
20db gain RCA.
Had about 10 odd hours of play back on different speakers. I think the thermal paste needs heat to settle as mines steady around 37C-39C Dropped about 4C since first turning it on.
By the way I clean with lint free cloths and use IPA alcohol just as Doodski explained (Thumbs up emoji)

 

[antcollinet]

I have several of them already delivered in two charges and don't know, if thermal paste has been applied during production or not. Thus I will have to unmantle them looking for that thermal paste. They seem to be getting rather warm or "hot", as stated by most of the users, who got them already and thermal paste improves coupling temperaturwise

Right - but that wont change the surface temperature of the device. It will only impact the internal temperature of the chips.


Power consumption is the same regardless of whether thermal paste is installed. It is power consumption that dicates how hot the amp gets overall. Paste is about getting power out of the chip with minimal chip temperature rise.

 

[rhing]

Oh very nice (turntable and cartridge)...!

I went for a Michael Fidler MMPro. Just got it, along with a balanced switch relay volume control. What stylus are you using with that V15 Type III? Just curious. Using an old Technics p205 myself (and a couple of others)... always hankered after an old V15 ... but not an option with that 'P' in front of the 205 (SL15).

Regardless, the V3 monos are a great match! No sense of anything lacking ... just a sense of everything being reproduced with power and transparency. Bargain indeed. Haven't tried the Muses02's. I'm sure I will at some point.

The Shure V15 Type III has the original VN35MR “Super Tracking” stylus. It’s a matter of time for replacing it, so I am prepared to acquire a suitable Jico replacement. The Dual 1229 is a family heirloom piece I inherited from my family. My uncle was an audiophile and he had an all McIntosh separates system with this Dual 1229 turntable. I sent it to Bill Neumann of Fix My Dual in Des Moine, Iowa. Bill is great to work with and his group restored the 50+ year old Dual 1229 idler wheel drive to “factory new” condition. I highly recommend him for purchasing rebuilt Dual turntables or rebuilding classic Dual turntables like the 1219, 1229 and 701.



With balanced connections from the phon stage preamp to the Fosi V3 Mono amps, my system is silent in idle and sounds very musical. I’m enjoying my vinyl.

 

[Doodski]

The Shure V15 Type III has the original VN35MR “Super Tracking” stylus. It’s a matter of time for replacing it, so I am prepared to acquire a suitable Jico replacement. The Dual 1229 is a family heirloom piece I inherited from my family. My uncle was an audiophile and he had an all McIntosh separates system with this Dual 1229 turntable. I sent it to Bill Neumann of Fix My Dual in Des Moine, Iowa. Bill is great to work with and his group restored the 50+ year old Dual 1229 idler wheel drive to “factory new” condition. I highly recommend him for purchasing rebuilt Dual turntables or rebuilding classic Dual turntables like the 1219, 1229 and 701.

View attachment 387232 View attachment 387233 View attachment 387234

With balanced connections from the phon stage preamp to the Fosi V3 Mono amps, my system is silent in idle and sounds very musical. I’m enjoying my vinyl.

That appears to be a nice system you arranged there. What is the big black amp?

 

[Jukka]

Nonsense, power is power independent of the “nationality”.

Power is often rated for 10 % distortion, but if quality is what you're after, then all Watts are not equal. If you look at Chinese web shops for the cheapest junk, you only see these inflated numbers.

 

[Doodski]

Power is often rated for 10 % distortion

WoW! Can you give examples so I can see the stuff they are offering with 10% distortion?

 

[rhing]

That is a Pass DIY Aleph J Class A SS amp I built during the COVID pandemic. I am a huge fan of Nelson Pass amplifiers including many of his Pass Labs, First Watt, Threshold and Adcom designs. The Aleph J gives my McIntosh MC240 tube amp a run for best sounding amps in my collection. I used high quality components including Kimber Kable internal wiring, Nichicon Muse capacitors, matched Vishay Dale resistors and original Toshiba JFETs. Surprisingly, it can drive my KEF LS50 speakers with its oversized power supply.



I also built a Pass DIY Class A amp using near-unobtainium NOS Sony VFET transistors with high quality components as well. That is a very special SS amp that sounds rich and warm like a tube amp, but with the speed and dynamic slam of a solid state amp.

I have been a Fosi Audio fan since purchasing a Fosi ZA-3 Class D amp last year. The V3 Monos are even more impressive with the PFFB and fully balanced topography. These measure very well against my DIY TPA3255 Class D stereo amp with PFFB.



This is essentially the same amp available as the Living Sounds Audio Discovery Warp-1 Class D amp designed by Viet Nguyen. He made his amp design available through diyAudio.com along with the balanced input buffer circuitry. The oversized switching power supply is a MicroAcoustics SMPS630-SO SMPS. The TPA3255 IC is mounted on the underside of the circuit board and thermally coupled to the 6mm Aluminum heat sink plate underneath and coupled to the perforated sheet metal base. This Class D amp is used in a system at my other home.

 

[Nopiano]

they all sound shite

Can you measure that? ;-)

 

[Doodski]

That is a Pass DIY Aleph J Class A SS amp I built during the COVID pandemic. I am a huge fan of Nelson Pass amplifiers including many of his Pass Labs, First Watt, Threshold and Adcom designs. The Aleph J gives my McIntosh MC240 tube amp a run for best sounding amps in my collection. I used high quality components including Kimber Kable internal wiring, Nichicon Muse capacitors, matched Vishay Dale resistors and original Toshiba JFETs. Surprisingly, it can drive my KEF LS50 speakers with its oversized power supply.

View attachment 387235 View attachment 387236

I also built a Pass DIY Class A amp using near-unobtainium NOS Sony VFET transistors with high quality components as well. That is a very special SS amp that sounds rich and warm like a tube amp, but with the speed and dynamic slam of a solid state amp.

I have been a Fosi Audio fan since purchasing a Fosi ZA-3 Class D amp last year. The V3 Monos are even more impressive with the PFFB and fully balanced topography. These measure very well against my DIY TPA3255 Class D stereo amp with PFFB.

View attachment 387237 View attachment 387238

This is essentially the same amp available as the Living Sounds Audio Discovery Warp-1 Class D amp designed by Viet Nguyen. He made his amp design available through diyAudio.com along with the balanced input buffer circuitry. The oversized switching power supply is a MicroAcoustics SMPS630-SO SMPS. The TPA3255 IC is mounted on the underside of the circuit board and thermally coupled to the 6mm Aluminum heat sink plate underneath and coupled to the perforated sheet metal base. This Class D amp is used in a system at my other home.

Very cool. I like the big amp the best of course. Nice assembly, very well laid out and organized. What kind of power output.

 

[Tell]

1) I dont like the nasally glass like tone/sound of the amps.

I've heard lots of weird audiophile words for describing audio, but "nasally glass like" really takes the price. What does that even mean?