Fosi Audio V3 Amplifier Review

[Doodski]

There appears to be a ghost image of what is apparently a heat sink.

 

[Doodski]

Yes, a metal plate is apparently used for a heat sink.

 

[Doodski]

With the metal plate heatsink used for the amp chip I recommend if a person is a enthusiast to use thermal paste between the chip amp and the heatsink. It will help especially with high power heat sinking for high current transients. Go for it!

 

[Lux_ury]

I've only noted two things:
Warranty invalidation not sure what it is?
Capacitor ratings usual power to volts ratio.
Interestingly my A07 does not feel hot but not sure if anything is actually touching the case in anyway.
Switching power bricks makes Interesting testing as it's only 32v 5A.

 

[Doodski]

I've only noted two things:
Warranty invalidation not sure what it is?
Capacitor ratings usual power to volts ratio.
Interestingly my A07 does not feel hot but not sure if anything is actually touching the case in anyway.
Switching power bricks makes Interesting testing as it's only 32v 5A.

What power supply bricks have you used? I need some current measurements at power supply max output current when the amplifier is at max output power. That way we can determine what is the actual max current at the respective power supply voltages in comparison to what people are using. That requires 2 multimeters. One for the current metering and the other to see what the power supply voltage sag is at max amplifier output power.

 

[Lux_ury]

What power supply bricks have you used? I need some current measurements at power supply max output current when the amplifier is at max output power. That way we can determine what is the actual max current at the respective power supply voltages in comparison to what people are using. That requires 2 multimeters. One for the current metering and the other to see what the power supply voltage sag is at max amplifier output power.

Only the 32v 5A one as the v3 will be arriving in a day or two. I'll provide whatever data you need once I've played about. (Thumbs up emoji)

 

[Doodski]

Only the 32v 5A one as the v3 will be arriving in a day or two. I'll provide whatever data you need once I've played about. (Thumbs up emoji)

CooL!

 

[strawberry644]

What power supply bricks have you used? I need some current measurements at power supply max output current when the amplifier is at max output power. That way we can determine what is the actual max current at the respective power supply voltages in comparison to what people are using. That requires 2 multimeters. One for the current metering and the other to see what the power supply voltage sag is at max amplifier output power.

speaking of this , I bought a Kill-a-Watt meter and no matter what volume I put on the dial or music played. it always says 10watts usage? tried both my 48v units and tested the original 32v and they all read 120vAC and about 0.2 A current for about a avg of 11w regardless of volume dial . wondering if my meter is broken or im going about this test wrong?

 

[flstaats]

Received Fosi V3, swapped in a pair of Sparkos SS3602 Op-Amps, and hooked it up with the provided 48.1V 5A power brick. Source is a Wiim Pro with an optical output at 24 bit / 48 kHz. Did a 17 point room correction with a miniDSP Flex with Dirac Live 3 which also acts as the DAC. The speakers are older (2006) but very good Paradigm Studio 40 with a Velodyne DD+ 10" servo subwoofer crossed over at 80 Hz. I've started my listening trials with the volume control on the miniDSP showing -20 db which is just about as loud as anything I ever listen to (the 1812 Overture Finale needed just a little more kick, but it would be too loud for my ears). Not enough time listening to have a strong opinion yet.

LOOKING FOR A POWER CONNECTOR:

I have a Meanwell HRPG-600-48 tuned to 51.0V and ~13A available to test. I ordered a DC5525 (5.5mm outer, 2.5mm) inner barrel to 14 gauge bare wire power cable (https://www.amazon.com/dp/B0BKFFRWT1) but it doesn't fit the power plug of Fosi V3, measured the outer barrel is exactly the same size, but the inner hole appears to be just a hair smaller than the plug on the Fosi power supply even though they are both nominally 2.5 mm. Any suggestions on a source for a large gauge wire plug that fits the Fosi V3? I would hate to have to sacrifice another perfectly good power supply just to get a plug that fits.

I would note all the DC5525 power plugs that I have found are only rated to 5A. I actually have a power supply that could provide 2X 300W which at 51V would actually be 11.8A... not that I would ever listen to anything with 10% THD. Mostly bought the power supply so it would never be the limit to the sound quality (very stiff stable current source).

My desire for the higher quality 51V / >10A power supply is not for huge continuous power but to give sufficient reserve current for transient impulses. Note: I use a DSP/DAC digital crossover at 80Hz to a powered subwoofer so the Fosi V3 does not drive the lower octaves. My speakers have nominal impedance of 8 Ohms which dips at some frequencies. With this Meanwell power supply and a couple days testing I can say there is a noticeable difference from the stock Fosi 48V / 5A power supply, but only in music with strong dynamic transients.

I've been in contact with Fosi Audio Support <[email protected]> in relation to two questions I asked (paraphrased below):

1) The specifications for the TPA3255 section 7.3 Recommended Operation Conditions (https://www.ti.com/document-viewer/TPA3255/datasheet/specifications#SLASE40749) calls for a typical operation voltage of 51V in 4 Ohms and 53.5V into 8 Ohms depending on what the overcurrent programing resistors Roc and Roc(latched) are set to. I asked them for the values of the resistors actually used (not wanting to disassemble and reverse engineer the board myself).

2) I've had trouble locating DC5525 (5.5MM x 2.5MM (External Diameter x Internal Diameter) large gauge wire plug that fits the Fosi V3 the one I found on Amazon (www.amazon.com/dp/B0BKFFRWT1 is the specified size but still doesn't fit).

The answer I got was as follows:
"...
1. You can use a maximum 48V power supply for this device.

2. I found that DC5525 power cable supports 12-24V DC voltage. (www.amazon.com/dp/B0BKFFRWT1) , the total power should not exceed 180W.
DC Jack Connector Size for V3 : 5.5MM x 2.5MM (External Diameter x Internal Diameter )
We haven't tried the 48V DC5525 to large gauge bare wire plugs to see whether it does work with the Fosi V3 power port or not.
I did some search, please check with the seller to see if it can be used for a 48V power supply.
https://www.amazon.com/Ancable-Repl...07K51T69V/ref=cm_cr_arp_d_pl_foot_top?ie=UTF8
.."

So given the official answer I've gotten from Fosi I've decided to go my own way with the understanding that it might void my warrantee. Frying the Fosi V3 would be no great loss for me given the price, but I don't want to create a hazard, damage other equipment, or start a fire. Experiments were in order.

According to the data sheet the maximum voltage supported by TPA3255 in 4-8 Ohm loads with all the specified overcurrent programming resistors is 51V, this is 6.25% greater than the supported 48V. In the provided specification this is the input voltage with the minimum THD+N into 4 Ohm and 8 Ohm loads. I've decided to tune my power supply to 51V with some additional precautions as outlined below.

Of course there are other considerations such as the the typical and max voltage range of the other components such as capacitors, inducers, resistors, the voltage regulator for the 12 V secondary supply, internal fusing, specified rating and heating of the power plug and leads, etc. I have found at least in the short run running at 51V / >10A has not caused any issues with the Fosi V3.

I already had the LUVMOXE power cable and found it didn't fit the Fosi V3, so I wound up ordering the Ancabel Power plugs. These plugs fit snugly into the Fosi V3 power receptacle with the following issues. The length of the shaft is a few mm too long... I've covered that portion with electrical tape so it isn't exposed. The back end of the plastic housing isn't wide enough to accommodate large gauge (14 awg) wires, and the soldering terminal stubs on the plug are not designed for the larger gauge. I trimmed the back end of the plug to allow the larger gauge. With careful soldering the connection, using the 14 gauge wires to reenforce the plugs electrical leads, and application of extra insulating electrical tape I had a suitable plug for the Fosi V3.

My Furman line conditioner (120V/15A at the AC wall socket) and Meanwell power supply (624W or 51V / ~12A on the DC line) provide two additional layers of overcurrent protection, in addition to the 15A circuit breaker on the power line and the built in Fosi V3 over current protection. The power supply and Fosi are mounted on an insulating surface. I've verified the case temperatures at high volume get warm but not hot to the touch (no fans needed) and that the power cable and custom power plug do not get warm at all (no hot spots).

Overall my setup with a miniDSP Flex (w/Dirac Live) as PEQ room correction/subwoofer crossover/DAC, and Fosi V3 with SparkOS 3602 Opamps and Meanwell 51V / >10A power supply sounds noticeably better to me than my failed NAD D3045 (I'm reusing my preexisting Wiim Pro streamer, 2006 Paradigm Studio 40 speakers, and Velodyne DD+ 10" 1125W subwoofer).

So I'm replacing my dead $800 amp with this $1100 setup including the $90 Fosi V3, was it worth it? For me it has been a clear yes. I really wanted to add the Dirac Live room correction and all the other amps I looked at with it built in cost far more than I spent. The PEQ/Dirac Live adequately compensates for for the slight frequency dependency of the Fosi V3 at the high end and improves the overall room sound. With the Meanwell power supply and the powered subwoofer the Fosi V3 has more than enough clean power for all the kinds of music I listen to in my medium size space. At all volume levels noise and distortion are not detectable to my ears, the sound is clean and clear. My biggest issue is the room configuration which is beyond my full control thus the need for Dirac Live room correction which really helped. This is not the typical setup for a Fosi V3 but I share the option for someone looking for room correction but not wanting to spend many $1000's for a fully integrated solution.

 

[Doodski]

speaking of this , I bought a Kill-a-Watt meter and no matter what volume I put on the dial or music played. it always says 10watts usage? tried both my 48v units and tested the original 32v and they all read 120vAC and about 0.2 A current for about a avg of 11w regardless of volume dial . wondering if my meter is broken or im going about this test wrong?

Volts (The Italian physicist Alessandro Volta (1745–1827)) is capitalized as are all the great contributors to physics. So is Watts and Amps. The Kill-a-Watt meter appears to be defective. They usually work from what I've read.

 

[flstaats]

My next project with the Meanwell HRPG-600-48 and Fosi V3 is to convert the 12V level trigger on the Wiim Pro using a relay to short the standby circuit on the power supply. The Fosi V3 stays warm when left on with the volume knob turned all the way up. But the Meanwell HRPG-600-48 has standby mode that can cut all power to the Fosi V3 and only uses 0.7W in the power supply itself. I want to see if this can work with the Fosi V3 without popping sound issues on startup and shutdown. Given the thermistor in the startup circuit I think it should be ok... just haven't tested yet.

 

[flstaats]

Volts (The Italian physicist Alessandro Volta (1745–1827) is capitalized as are all the great contributors to physics. So is Watts and Amps. The Kill-a-Watt meter appears to be defective. They usually work from what I've read.

You need to consider the steady state current (what most power meters measure) and the transient power. Audio signals can have low steady state power as read on the meter but much high power transients. Transient response of power supplies varies greatly... the Fosi 48V supply is actually very good for the price. There are several posts in this thread about how the transient power using it is much better than the rated 240 watts.

 

[Doodski]

You need to consider the steady state current (what most power meters measure) and the transient power. Audio signals can have low steady state power as read on the meter but much high power transients. Transient response of power supplies varies greatly... the Fosi 48V supply is actually very good for the price. There are several posts in this thread about how the transient power using it is much better than the rated 240 watts.

I want the maximum RMS power output @ clipping amperage from a proper multimeter for each power supply voltage setting. A peep with a 48 V DC power supply that can be dialed down to 28 V DC and 34 V DC and anything in between can perform these amps measurements. The rest can be determined from what I figure. I'm not looking for calibration NIST numbers. Just looking for 1 decimal place or maybe 2 of resolution if really looking like required.

 

[Lux_ury]

Just arrived 12 days in transit.
So far the unit is definitely beefier than the A07.
Using my Infinity RS7b 3 way ribbon tweeters.
Bright and forward bass is tight and good.
I can't comfortably turn this up past 12.00 O'clock. My listening room is pretty less than one metre from me on a lounger.
What I can say off the bat is the separation is super compares to more expensive amps.
48v 5a makes a whole different system compared to the 32v A07, but saying that A07 makes me want more power with the balance its got.
It's subjective especially with my aging ears, but from me we'll done Fosi, pink panther has stolen the jewel crown for this segment of D class price point. (Laugh emoji)
D10 dac optical
Bluetooth adaptor
48v 5amps
V3
240v domestic supply

Edit: Ambient temps 21.9 & 22C
Running for 2hrs around 12.00 O'clock volume
Max 31.5C to 32C
Min ambient start first recording after 2hrs 29C.
Prob top of case.
Prob bottom: quick reading 33.5C to 34C

 

[cyclo]

I have the V3 powering the front speakers with volume pot set to maximum... The actual levels set on my Marantz Pre Processor. With the V3 powering 4-6 ohm speakers hooked up to it, the temps go up to 40C (measuring from the top of the case) and stays there. Simply putting a 120mm AC Infinity cooling fan to blow air from the sides (at the fans lowest/quietest setting which is barely audible) lowers this temp to around 29C max (room ambient temp is 24C). From my experience, if your V3 is used on power hungry and/or low impedance speakers, the best way to cool it is to just get cool air blowing on it... The vents do help in getting rid of the warm air inside the case.

 

[MNMList84]

I do not understand what is "load dependencies" issue. I am hoping someone can advise if this Fosi V3 would be a good match for my SoundArtist LS3/5a which has an impedance of 11 ohms.

 

[Lux_ury]

I do not understand what is "load dependencies" issue. I am hoping someone can advise if this Fosi V3 would be a good match for my SoundArtist LS3/5a which has an impedance of 11 ohms.

"Since impedance is a measure of how much the speaker resists current, the lower the impedance in ohms, the more power the speaker will draw from your receiver. Because of that, a 4 ohm speaker is considered more “power hungry” and will tax your amp more than a 6 or 8 ohm speaker."

 

[MNMList84]

"Since impedance is a measure of how much the speaker resists current, the lower the impedance in ohms, the more power the speaker will draw from your receiver. Because of that, a 4 ohm speaker is considered more “power hungry” and will tax your amp more than a 6 or 8 ohm speaker."

Thank you for your explanation.

 

[Lux_ury]

Thank you for your

Your asking a dicy question it's loaded one sorry for the pun. Some will say its not dependant upon loads Some will say its is and I can hear it. Some will say crossover, silver coated wires etc change the frequency sound dependant upon load and matching of amp and speaker etc. I keep it simple it has synergy or it doesn't I like it or I don't. Someone will proceed to produce a graph that will say contry to that difference or not. New speakers as new amplifiers are made to match as much as ohms law will permit. The curve it matches closer to 6ohms or 8ohms, but problems arise when you add load or music as the frequency is never the same load.
I could be talking rubbish and I'm sure someone will have data stating that fact (Smile emoji)

 

[ModDIY]