Fosi Audio V3 Mono Amplifier Review

[SMen]

No, not necessarily. Many subs have a grounded black terminal for high level inputs - which is not compatible with a class D amp with bridge tied load such as this one. Best to check with the sub manufacturer.

In that case it is usually possible to connect one speaker terminal to the red channel of the sub, and connect the black terminal of the sub back to an earth point on the amp - ususallly the ring of an unused RCA connector. However, again it is necessary to check with the sub manufacturer the compatibility of this approach.

Am I right that this is the case with the vast majority of class D, so these Fosi monos are not at all unusual, and it would be the same with say, an Aiyima A07.

I have speaker level inputs and the manufacturers advice is to make sure that the line levels are not connected at the same time.
But another manufacturer (REL) suggested connecting with the line level to line level, but with the line level volume down.

So quite confusing.

 

[gwing]

Am I right that this is the case with the vast majority of class D, so these Fosi monos are not at all unusual, and it would be the same with say, an Aiyima A07.

I have speaker level inputs and the manufacturers advice is to make sure that the line levels are not connected at the same time.
But another manufacturer (REL) suggested connecting with the line level to line level, but with the line level volume down.

So quite confusing.

Yes this is a common problem with many class D amps. Not that the problem is exclusive to class D but it is much less common for 'conventional' amps to be bridged.

I know REL say different, but generally using line level connections to the sub is the best way to go instead of using speaker level connections.

 

[SMen]

Yes this is a common problem with many class D amps. Not that the problem is exclusive to class D but it is much less common for 'conventional' amps to be bridged.

I know REL say different, but generally using line level connections to the sub is the best way to go instead of using speaker level connections.

Yes I am using MJ Acoustics, and have for years. They were fine with both the Ayima A07 and A08 attached solely with one or other connection but not both (obviously I did not try both having read this). I agree about the line level being safer, but I'm geared up with Speakon cables.

This is their warning that I have kept.

 

[Lednek]

Yes I am using MJ Acoustics, and have for years. They were fine with both the Ayima A07 and A08 attached solely with one or other connection but not both (obviously I did not try both having read this). I agree about the line level being safer, but I'm geared up with Speakon cables.

This is their warning that I have kept.

Is this not specifically for connecting LFE(line level sub out) and speaker connections simultaneously? Do you even have a line level sub output? Under what circumstance would someone want both LFE and speaker level inputs hooked up simuopiniously. Obviously the manufacture saw a case, but I don't. Can someone help me understand how a bridged load amplifier cares about grounding at the soeaker level. Isn't it just a red and black wire going to the speaker? In other words, if you switch them does something other than a 180 degree phase shift happen?

 

[SMen]

Is this not specifically for connecting LFE(line level sub out) and speaker connections simultaneously? Do you even have a line level sub output? Under what circumstance would someone want both LFE and speaker level inputs hooked up simuopiniously. Obviously the manufacture saw a case, but I don't. Can someone help me understand how a bridged load amplifier cares about grounding at the soeaker level. Isn't it just a red and black wire going to the speaker? In other words, if you switch them does something other than a 180 degree phase shift happen?

Yes it has both. It can be useful for combining a stereo set up with an audio visual set up. You can optimize the volume and response levels differently for each and then whichever is 'in play' works through the subs.

I'm also interested in your question though, as to why exactly something as simple as a speaker level connection causes problems. I understand the alert from MJ Acoustics not to connect line level and speaker at the same time but this conflicts completely with REL's suggestion to do the exact opposite! In other words MJ Acoustics just say don't run a dual input system - just one or the other.

 

[rvsixer]

Is this not specifically for connecting LFE(line level sub out) and speaker connections simultaneously? ... Under what circumstance would someone want both LFE and speaker level inputs hooked up simuopiniously.

I suppose it would be possible to route LFE via line level sub out to a dedicated sub(s), and to run bass managed channels to a separate dedicated sub(s) via speaker level. I personally would never use speaker level input into a sub (I've not met a sub amp having enough flexibility for full manual integration, and question the quality of their speaker-to-line level converters).

I just run the normal setup (preamp line level sub output is used for both bass managed channels and the LFE channel). And a simple HT bypass to integrate stereo 2.x/HT systems (will be even easier using Fosi with its switchable dual input).

 

[Lednek]

Yes it has both. It can be useful for combining a stereo set up with an audio visual set up. You can optimize the volume and response levels differently for each and then whichever is 'in play' works through the subs.

I'm also interested in your question though, as to why exactly something as simple as a speaker level connection causes problems. I understand the alert from MJ Acoustics not to connect line level and speaker at the same time but this conflicts completely with REL's suggestion to do the exact opposite! In other words MJ Acoustics just say don't run a dual input system - just one or the other.

In my theater setup(Denon x3400) I crossover everything at 80hz as I have some decent subs(Monolith 12's) and want to take as much load off the amplifier. I will be using three v3 monos for the front stage. My plan is to continue to use the crossed over sub outs for everything. I will also run a balanced input from my DAC for a pure 2 channel experience for the fun of it. If I were to run both line and speaker level inputs to the subs, not only would I have to flip a switch on the subwoofers. The V3 Monos will have enough power to run full frequency to my towers for the occasional 2 channel listen in the theater. I do have a dedicated 2 channel system with subs as well, so I haven't realy considered dual inputs to my theater subs.

 

[Deleted member 72219]

Off the back of your latest crowdfunding update, @Fosi Audio You guys may want to re-examine your relationship with Verum. See Post in thread 'Verum , racist and vile please don't give him business.'
https://audiosciencereview.com/foru...lease-dont-give-him-business.4494/post-469489

 

[Cal_Cobra]

Yes it has both. It can be useful for combining a stereo set up with an audio visual set up. You can optimize the volume and response levels differently for each and then whichever is 'in play' works through the subs.

I run a separate dedicated stereo system from my home theater system, and have thought about sharing the subs from my home theater system with the dedicated stereo system.

 

[Lednek]

I run a separate dedicated stereo system from my home theater system, and have thought about sharing the subs from my home theater system with the dedicated stereo system.

I guess you could adjust the sub output to match your 2 channel, and let the avr processor do the equalization for the multichannel. Just a flip of the switch between sub inputs.

 

[rgruber]

My experience going from a well reviewed at the time class A/B Rotel 1520 to first a Crown XLS 1002 and then an XTZ-Edge A2 300 (both class D) was a profound improvement in sound.

The clarity and general oomph of the system was not subtle. It could have just been that more power woke up my speakers (the Rotel was rated at 60 watts per channel) versus the Crown and the XTZ being more like 300 watts per channel (depending on how much you trust these power ratings) but I would say if the Fosi is anywhere near it's rated power, you could have a really significant improvement. For me it was like going from having the sound coming from down the hall to having the sound be in front of my face. I've since brought another more powerful class A/B (Denon PMA 1700 NE) but still prefer the sound the XTZ . The detail in the midrange and treble and the control and power of the bass is just better to my ears. I think some people have a preference for the warmer sound of class A/B but for me I prefer the clarity, dark background and punchier bass of class D.

Hello everyone,
I plan to purchase these monoblocks as a replacement for my oldschool AV-Receiver onkyo TX-SR700 (from 2002 at original price around 800$). I'm currently running it (in stereo mode) as a temporary replacement for my original power amp (same price range and even slightly older than the onkyo), which has definitely gone to silicon heaven.

Based on the parameters and amirm measurements, it should be a significant improvement for me. Unfortunately, I don't have personal experience with any D-Class amplifier yet. Is there a chance that even with these "cheap" boxes I will really move up in sound quality?

 

[Doodski]

The clarity and general oomph of the system was not subtle. It could have just been that more power woke up my speakers (the Rotel was rated at 60 watts per channel) versus the Crown and the XTZ being more like 300 watts per channel (depending on how much you trust these power ratings) but I would say if the Fosi is anywhere near it's rated power, you could have a really significant improvement. For me it was like going from having the sound coming from down the hall to having the sound be in front of my face. I've since brought another more powerful class A/B (Denon PMA 1700 NE) but still prefer the sound the XTZ . The detail in the midrange and treble and the control and power of the bass is just better to my ears.

That sounds about right when using a very high power amp on difficult loads/speakers.

I think some people have a preference for the warmer sound of class A/B but for me I prefer the clarity, dark background and punchier bass of class D.

I'm not so sure about this claim though. But you did go from a 60W/ch amp to hundreds of watts. Have you been able to do a A/B blind listening test with a switchbox to compare the amps?

 

[gwing]

Is this not specifically for connecting LFE(line level sub out) and speaker connections simultaneously? Do you even have a line level sub output? Under what circumstance would someone want both LFE and speaker level inputs hooked up simuopiniously. Obviously the manufacture saw a case, but I don't. Can someone help me understand how a bridged load amplifier cares about grounding at the soeaker level. Isn't it just a red and black wire going to the speaker? In other words, if you switch them does something other than a 180 degree phase shift happen?

With RCA red carries the signal and black is ground.

With a bridged amplifier the red and black can carry + and - signals with neither being tied to ground.

 

[rgruber]

No. Nor will I.

I listened to the Crown and the Rotel back to back and it wasn't even close. The Rotel is sitting in my storage unit. I replaced the Crown with the XTZ more for aesthetics than sound. Sound was similar with the XTZ having a darker background and less audible distortion (the more pricey Crown's have less distortion than the 1002).

I've done more intense listening between the Denon and the XTZ. The differences are more subtle but still apparent. I had the Denon in my system for several months (bought as my wife really wanted an integrated to simplify listening to music rather than the frankenstein tube pre-amp with linear power supply into the XTZ power amp I had before) and I just felt like something was missing. I hooked up the XTZ again but removed the tube pre, just went straight from my DAC and whatever was missing was back in spades. Mostly clarity, nuance and bass punch for which I sacrificed a bit of smoothness and warmth in female vocals in particular.

So admittedly non-scientific. I could live with either but definitely prefer class D.

The argument could be made that perhaps it's just having gobs of power on tap makes a bigger difference than people generally acknowledge.

That sounds about right when using a very high power amp on difficult loads/speakers.

I'm not so sure about this claim though. But you did go from a 60W/ch amp to hundreds of watts. Have you been able to do a A/B blind listening test with a switchbox to compare the amps?

 

[Jim Taylor]

I listened to the Crown and the Rotel back to back and it wasn't even close

So admittedly non-scientific.

Very true. More importantly, it's not controlled. Because of the nature and strength of our biases, comparisons (in audio or any other sensory group) must be conducted under rigorous controls. This keeps the Evil Bias Monster ) at bay, and allows us to draw conclusions more in line with reality.

There are many biases. They are used by our mind for fast and useful (but not necessarily accurate) reactions to stimuli, in order to survive.

Here is a list.

Jim

p.s. - I have seen some people scan through that list, pointing out certain biases and saying, "Yup, that one applies to me. And here's another one that applies to me, too." That's not the way bias works. They ALL apply to each and every one of us, although not mixed in the same degree of strength.

 

[Doodski]

The argument could be made that perhaps it's just having gobs of power on tap makes a bigger difference than people generally acknowledge.

Well... The argument can be made for any amp really... Plus you went to a powerhouse amp and that is going to change stuff.

 

[Lednek]

With RCA red carries the signal and black is ground.

With a bridged amplifier the red and black can carry + and - signals with neither being tied to ground.

This would explain the problem with simultaneous low and high level hookups. But when running only speaker level connections to a subwoofer, how can the subwoofer or speaker for that matter differentiate a bridged amplifier from a non bridged?

 

[Sokel]

This would explain the problem with simultaneous low and high level hookups. But when running only speaker level connections to a subwoofer, how can the subwoofer or speaker for that matter differentiate a bridged amplifier from a non bridged?

The speaker or the sub won't know.
If you're lucky and the amp is protected from such event it will go into protection.
If not,well...

 

[antcollinet]

This would explain the problem with simultaneous low and high level hookups. But when running only speaker level connections to a subwoofer, how can the subwoofer or speaker for that matter differentiate a bridged amplifier from a non bridged?

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.

 

[Lednek]

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.

Thank you. I was looking at it completely backwards. Like what could it possibly do to the subwoofer. Thanks for expanding my understanding and saving someone from my hasty response.