Fosi Audio V3 Mono Amplifier Review

[SMen]

Lets say the sub connects one of the speaker terminals to ground.

Lets say the amp connects the same speaker terminal to +50V (or even -50V)

Now you have a short circuit. If you are lucky the short circuit protection kicks in, and the amp shuts down (if it has short circuit protection). If you are unlucky the magic smoke is ejected.

So this begs the question does the fosi v3 mono have such protection (or possibly you mean the one in the powered subwoofer it occurs to me)

 

[Sokel]

So this begs the question does the fosi v3 mono have such protection (or possibly you mean the one in the powered subwoofer it occurs to me)

Don't know about the amp but it's chip does:



That's always under sensible conditions of course.

 

[somebodyelse]

More detail from the tpa3255 datasheet which seems to address similar situations:

9.4.1.3 DC Speaker Protection
The output DC protection scheme protects a speaker from excess DC current in case one terminal of the
speaker is connected to the amplifier while the other is accidentally shorted to the chassis ground. Such a short
circuit results in a DC voltage of PVDD/2 across the speaker, which potentially can result in destructive current
levels. The output DC protection detects any unbalance of the output and input current of a BTL output, and in
the event of the unbalance exceeding a programmed threshold, the overload counter increments until its
maximum value and the affected output channel is shut down. DC Speaker Protection is disabled in SE mode
operation.

 

[ovi]

Check this out, may be useful:

Fosi Audio V3 Mono Amplifier Review

That's amazing, thanks for the review. I would pair three of those with an Onkyo rz-50. Since I have to buy cables anyway, are there any benefits in going rca-xlr vs rca-rca? According to Amir's review of the rz-50, it can output up to about 3.5 volt

www.audiosciencereview.com

May I ask a follow-up question? I'm still trying to wrap my head around it.

According to Fosi, the v3 mono can output 160W @ 6Ω with a 48V/5A PSU. So the formula would be one of these two using RCA and the 25/31 dB gain settings:

sqrt(160*6)*10^(-25/20)=1.74Vrms or sqrt(160*6)*10^(-31/20)=0.87Vrms

I have connected a RPI streamer via USB to a SMSL SU-1 DAC via RCA at 31dB gain settings. SMSL SU-1 has an output level of 2Vrms
Since neither the Fosi v3 mono nor the SMSL SU-1 DAC has volume controls, I control the volume via the RPI.

Q1: Is this a viable setup, I mean can the SMSL SU-1 fully satisfy the Fosi v3 mono's requirements?
Q2: Is my volume handling “alright”? I quite like only having one point of control for volume.
Q3: Can I get the full 160W power of the two Fosi v3 Monos with this setup provided the speakers support it?

 

[gwing]

So this begs the question does the fosi v3 mono have such protection (or possibly you mean the one in the powered subwoofer it occurs to me)

I think it begs the thought "just use a line level output" not the Fosi (or any other Tp3255 chip) amp's speaker level outputs. You really don't want to be driving the chip into protection, not if you don't want smoke - potentially shorting out that 48v output to earth isn't a good idea for any amplifier.

 

[gwing]

May I ask a follow-up question? I'm still trying to wrap my head around it.

According to Fosi, the v3 mono can output 160W @ 6Ω with a 48V/5A PSU. So the formula would be one of these two using RCA and the 25/31 dB gain settings:

sqrt(160*6)*10^(-25/20)=1.74Vrms or sqrt(160*6)*10^(-31/20)=0.87Vrms

I have connected a RPI streamer via USB to a SMSL SU-1 DAC via RCA at 31dB gain settings. SMSL SU-1 has an output level of 2Vrms
Since neither the Fosi v3 mono nor the SMSL SU-1 DAC has volume controls, I control the volume via the RPI.

Q1: Is this a viable setup, I mean can the SMSL SU-1 fully satisfy the Fosi v3 mono's requirements?
Q2: Is my volume handling “alright”? I quite like only having one point of control for volume.
Q3: Can I get the full 160W power of the two Fosi v3 Monos with this setup provided the speakers support it?

You'll be fine. If the SU1 is sending a 2V signal to the v3 on RCA it will be capable of driving it to full volume.

Personally though, I like to have a volume knob somewhere in the chain and wouldn't be comfortable just having the Pi for control, I do suggest setting the v3 to minimum gain, at least to start with.

 

[SMen]

I think it begs the thought "just use a line level output" not the Fosi (or any other Tp3255 chip) amp's speaker level outputs. You really don't want to be driving the chip into protection, not if you don't want smoke - potentially shorting out that 48v output to earth isn't a good idea for any amplifier.

I've had no problems with either the A07 or the A08 which are BTL - no additional heat or such either, so I think that I should expect the same with the Fosi Monos (with my particular subwoofers).

 

[gwing]

I've had no problems with either the A07 or the A08 which are BTL - no additional heat or such either, so I think that I should expect the same with the Fosi Monos (with my particular subwoofers).

Good luck

Although, to be fair, I'm also good running speaker level connections from a little DDA amp (sta326) to an equally tiny REL sub - but I would use line level if I could. I'm certainly not planning to do the same with my monos.

 

[ovi]

You'll be fine. If the SU1 is sending a 2V signal to the v3 on RCA it will be capable of driving it to full volume.

Personally though, I like to have a volume knob somewhere in the chain and wouldn't be comfortable just having the Pi for control, I do suggest setting the v3 to minimum gain, at least to start with.

Thanks. I mostly listen via Spotify Connect, so I control the volume from my Spotify Android app. The RPI runs moode audio and is set to allow max 60/100 volume. This all works out fine in practice, I was just double-checking with you guys. Also, sometimes when running late, I play music for my dog at home, so I need to be able to fully control the volume from my phone and be 100% sure what the output level will be.

 

[SMen]

Good luck

Although, to be fair, I'm also good running speaker level connections from a little DDA amp (sta326) to an equally tiny REL sub - but I would use line level if I could. I'm certainly not planning to do the same with my monos.

Back in the day with REL and MJ Acoustics the speaker connection was the favoured one (often).

It's a moot point though for the V3 mono set up, that if you are in fact going to use the line level to run a subwoofer, you need a pre-amp with a line level subwoofer out.

 

[HoweSound]

Dumb question: I have two of these coming. The XLR connector port on the V3 looks different than the standard XLR connectors on my other equipment. Is this some kind of mini XLR? will I need a hybrid cable to plug these into my Freya S pre-amp?

 

[Deleted member 72219]

Dumb question: I have two of these coming. The XLR connector port on the V3 looks different than the standard XLR connectors on my other equipment. Is this some kind of mini XLR? will I need a hybrid cable to plug these into my Freya S pre-amp?

Fosi uses a type of port that accepts BOTH, standard XLR as well as TRS balanced connectors. You’ll be fine with your standard XLR cables.

-Ed

 

[GoDawgs]

I'm curious about these Muse02 op amps that Fosi is throwing in with the V3 mono Kickstarter orders. I do believe the Kickstarter hit $500,000, so I believe we get 2 op amps per order (not per amp). Why should getting 2 op amps per order be a reward if, (as some folks have written in other threads), swapping op amps is normally ill advised and even risky in some instances? Are these Muse02 op amps properly matched with the existing V3 Mono amp components? Are these any real noticeable improvement to the amp output or will they be just a hobby test listen where I may get to say things like "detail", "fast", "wider stage", and other neat-o audio descriptive phrases?

By following this thread I think I understand that each V3 mono (I ordered 2), has 2 op amps that may positively affect sound if swapped. Even if I want to try swapping op amps I wouldn't get the full effect without buying another $120 worth of op amps (2 more Muse02s)? I was all ready to give it a try until I figured out I could only do one V3 mono amp without sinking more money. Would swapping one of the op amps in each V3 mono even be worth the labor of opening the case? (Would swapping both be worth it?)

I'll think I'll wait and hopefully some other folks will attempt to determine if their Muse02 op amp offers a real reward vs. just a possible slight change in sound.

But I will say thanks for the XLR cables Fosi, and I would wear an size XL t-shirt if it came with my order.

 

[SMen]

I'm curious about these Muse02 op amps that Fosi is throwing in with the V3 mono Kickstarter orders. I do believe the Kickstarter hit $500,000, so I believe we get 2 op amps per order (not per amp). Why should getting 2 op amps per order be a reward if, (as some folks have written in other threads), swapping op amps is normally ill advised and even risky in some instances? Are these Muse02 op amps properly matched with the existing V3 Mono amp components? Are these any real noticeable improvement to the amp output or will they be just a hobby test listen where I may get to say things like "detail", "fast", "wider stage", and other neat-o audio descriptive phrases?

By following this thread I think I understand that each V3 mono (I ordered 2), has 2 op amps that may positively affect sound if swapped. Even if I want to try swapping op amps I wouldn't get the full effect without buying another $120 worth of op amps (2 more Muse02s)? I was all ready to give it a try until I figured out I could only do one V3 mono amp without sinking more money. Would swapping one of the op amps in each V3 mono even be worth the labor of opening the case? (Would swapping both be worth it?)

I'll think I'll wait and hopefully some other folks will attempt to determine if their Muse02 op amp offers a real reward vs. just a possible slight change in sound.

But I will say thanks for the XLR cables Fosi, and I would wear an size XL t-shirt if it came with my order.

Now that is a right old can of worms you've opened there
..

For me never mind all the technical arguments over this - it is the points you raise over the confusions. One per order or one per unit?
Why get people to open up their units for one per order, or for that matter one per unit?!

Can you imagine any manufacturer justifying different op amps on a parallel output stage using two?

There is no icon for "can of worms" available as far as I am aware, but imagine one here:
or here :

 

[DavidM1]

Fosi language around the op amps is careful not to spell out any actual advantage. I don’t think this little accessory market would even exist if it required soldering skills.

People foolishly assume a price-quality relationship in the absence of other information.

 

[Negatywny]

oh shit here we go again....
To put it short, what is the difference with opamp type A costing 5$ with SINAD 100, and opamp type B costing 50$ with SINAD 100?

 

[SMen]

oh shit here we go again....
To put it short, what is the difference with opamp type A costing 5$ with SINAD 100, and opamp type B costing 50$ with SINAD 100?

It's such fun.... no Fosi on this single op amp offer for parallel circuit which require two ... and then it might be one op amp offered for four required across the two monoblocks .. this is crazy. It sows disharmony. Confusion. Dare I say it, it is taking the piss! (which in english means "vraiment la merde")

 

[rgruber]

If you're interested in diving into this particular rabbit op amp hole:

The really interesting thing in this is where he solders together two cheap op amps and is very impressed with the sound. Put on some headphones and see if you come away hearing any differences.

 

[GoDawgs]

If you're interested in diving into this particular rabbit op amp hole:

The really interesting thing in this is where he solders together two cheap op amps and is very impressed with the sound. Put on some headphones and see if you come away hearing any differences.

OOhhh, now I don't get it even more . That was some video. I do believe someone here will report on their results eventually and if they are over the top raving about these, maybe I'll do my left channel.

 

[DavidM1]

. It sows disharmony. Confusion. Dare I say it, it is taking the piss!

No. It is handing out a sample size in the hope of making sales down the track.

Op amps are the new go to for the scientifically disinclined.