Fosi v3 Mono - User Impressions | Owner's Thread

[Skeptical_Aus]

Another issue with high level sub configuration is when the speakers are very efficient. Since you don't need much current to drive them the high level signal is still quite low and so the sub volume is hard to get right. With most speakers with sensitivity in the 80 dB to 85 dB range this issue does not occur. For that reason it it's better to use a line level input if you can. In my system I use a Topping A90 as a preamp sending the XLR out the V3 monos and RCA to my SVS sub. That works really well.

 

[Deleted member 72219]

Another issue with high level sub configuration is when the speakers are very efficient. Since you don't need much current to drive them the high level signal is still quite low and so the sub volume is hard to get right. With most speakers with sensitivity in the 80 dB to 85 dB range this issue does not occur. For that reason it it's better to use a line level input if you can. In my system I use a Topping A90 as a preamp sending the XLR out the V3 monos and RCA to my SVS sub. That works really well.

He’s using Magnepan LRS+, which is why he was doing fine with those high level inputs with his original amplifier (PS Audio HCA-2). Personally, I’ve always used line level input from my preamp as well, but he fancied the nonsense, “benefits,” of using high level inputs. Made no sense to me, if you’re able to connect a subwoofer at the preamp, why connect it farther down the chain so that there’s more crap in the signal path before the sub?

-Ed

 

[SMen]

He’s using Magnepan LRS+, which is why he was doing fine with those high level inputs with his original amplifier (PS Audio HCA-2). Personally, I’ve always used line level input from my preamp as well, but he fancied the nonsense, “benefits,” of using high level inputs. Made no sense to me, if you’re able to connect a subwoofer at the preamp, why connect it farther down the chain so that there’s more crap in the signal path before the sub?

-Ed

Another issue with high level sub configuration is when the speakers are very efficient. Since you don't need much current to drive them the high level signal is still quite low and so the sub volume is hard to get right. With most speakers with sensitivity in the 80 dB to 85 dB range this issue does not occur. For that reason it it's better to use a line level input if you can. In my system I use a Topping A90 as a preamp sending the XLR out the V3 monos and RCA to my SVS sub. That works really well.

To HT or Not To, That is the Question - REL Acoustics UK

We’ve just brought out our second generation of our Serie HT and, no surprise, they’re incredible in theatre applications. Natch. But it turns out we also

rel.net

I looked up Richard Lord and came across this link in REL's blog.

"Long ago, Richard Lord reasoned that using your power amp’s speaker output terminals to drive the front end of a subwoofer should allow it to sound exactly the same as your speakers because it was being fed exactly the same signal. And that’s absolutely true.
Right up until the efficiency of a speaker becomes so great that a high-level input isn’t being fed a strong enough signal to the input of your REL".

 

[Guddu]

 

[Deleted member 72219]

View attachment 383612

Good, so they’ll fix it for single-ended users and f*ck it up for balanced input users. Much appreciated, @Fosi Audio

-Ed

 

[Sokel]

Good, so they’ll fix it for single-ended users and f*ck it up for balanced input users. Much appreciated, @Fosi Audio

-Ed

They still don't get what happens.
Sad really.

 

[gwing]

They still don't get what happens.
Sad really.

Let's not jump to conclusions. Fosi just say "We'll modify the mono so that the phase markings match the output" but that doesn't tell us anything about whatthey actually intend to do.

The fear is of course that @Fosi Audio have misunderstood the problem and will just change the markings and the colour of the terminals which won't help at all, what *is* required is changing the design so that both RCA and XLR inputs give the same output polarity, preferably non-inverted. The statement made above by Fosi doesn't tell us what they actually intend to do so there may be hope yet.

 

[Sokel]

Let's not jump to conclusions. Fosi just say "We'll modify the mono so that the phase markings match the output" but that doesn't tell us anything about whatthey actually intend to do.

The fear is of course that @Fosi Audio have misunderstood the problem and will just change the markings and the colour of the terminals which won't help at all, what *is* required is changing the design so that both RCA and XLR inputs give the same output polarity, preferably non-inverted. The statement made above by Fosi doesn't tell us what they actually intend to do so there may be hope yet.

Based on what they describe as the solution (mark the polarity and NOT changing the circuit) it seems that they don't get that there are two different polarities depending the input.

The only viable way I can see that happening without changing the insides is double markings,both black or red binding posts and a riddle left to the end users to solve.

 

[gwing]

Based on what they describe as the solution (mark the polarity and NOT changing the circuit) it seems that they don't get that there are two different polarities depending the input.

The only viable way I can see that happening without changing the insides is double markings,both black or red binding posts and a riddle left to the end users to solve.

The only viable fix is going to be to change the insides so that both inputs have the same polarity.

Or just say it isn't a problem and explain the issue thoroughly in the instructions so that anyone can understand (good luck with that though). And maybe colour the outputs something like Blue/Yellow so that nobody has any idea what that means until they have read your explanation in the manual.

 

[JeremyFife]

The only viable fix is going to be to change the insides so that both inputs have the same polarity.

Or just say it isn't a problem and explain the issue thoroughly in the instructions so that anyone can understand (good luck with that though). And maybe colour the outputs something like Blue/Yellow so that nobody has any idea what that means until they have read your explanation in the manual.

A simple statement, like;

For balanced use, Blue = Red and Yellow = Black. For unblanced (RCA) use then Blue = Black and Yellow = Red. In either case the opposite can also safely apply. If you use your Fosi Mono's with other equipment in your system - including, but not limited to, powered sub-woofers or any other amplifiers - then the same rule may apply, or it could be the opposite. We can't comment on what is White, or not.
n.b. This entire statement can also quite simply and safely be reversed, or vice versa.

 

[Guddu]

A simple statement, like;

For balanced use, Blue = Red and Yellow = Black. For unblanced (RCA) use then Blue = Black and Yellow = Red. In either case the opposite can also safely apply. If you use your Fosi Mono's with other equipment in your system - including, but not limited to, powered sub-woofers or any other amplifiers - then the same rule may apply, or it could be the opposite. We can't comment on what is White, or not.
n.b. This entire statement can also quite simply and safely be reversed, or vice versa.

While you are correct suggesting simpler operating procedure for good, and existing owners should be able to try & use it, keeping this in check for long time and specially for those who keep on disconnecting/connecting (for any reason) is not error free.
Any equipment should follow what’s printed on the equipment, and here the only proper solution is to correct it on equipment in any way possible.
Now this has become a known issue but only for those who are following ASR continuously, but all rest might not have any clue.

 

[Jon L]

They still don't get what happens.
Sad really.

Man, Fosi so far has been praised so much for interacting with customers on line and being responsive, but this...

 

[jbaumann]

I honestly don‘t understand the problem that all of you have.

My Concentra II (Jeff Rowland) inverts, and that is nowhere to be found in the documentation. You have to measure it when combining with a sub, and that amplifier is 20 years old. So this is hardly new, and it is hardly a problem, apart from the decision whether to invert the output of the amp when connecting to the loud speakers.

Something like @Guddu‘s suggestion might help some, but irritate others when they do not see the usual colors on the binding posts.

Fosi is really trying to be responsive and trying to fix this by documenting it in detail. Please keep in mind that English is not the first language for many of the engineers there, and if there seems to be a communication problem, that might be part of it.

I really like these small amps and I‘m amazed that they can hold their ground against my big amp. They even seem to have a slightly bigger sound stage (which I really find astonishing).

I‘m not happy with the temperature (around 42°C in my case), and it might suggest that the implementation of the PFFB could be reworked. But I look forward to what FOSI can determine there. And they are pushing the envelope all the time, so even if this is only an intermediate step, it is good that they are doing it.

If you take into account that these amps cost an order of magnitude less than other amps with the same sound quality, then it is really fantastic what FOSI does.

TL;DR: Don‘t focus in minor issues like the binding post color or whether one input is inverted, but on the big picture, a Class D amp that provides the same sound quality as big amps for a fraction of the price.

But that is only my view. And I‘m in no way associated with FOSI, I‘m only a happy customer (even though they still haven‘t sent me my second XLR cable…).

 

[Guddu]

They even seem to have a slightly bigger sound stage (which I really find astonishing).

Happy reading it, but I never thought sound stage has anything or much to do with amplifier.

I‘m not happy with the temperature (around 42°C in my case), and it might suggest that the implementation of the PFFB could be reworked. But I look forward to what FOSI can determine there. And they are pushing the envelope all the time, so even if this is only an intermediate step, it is good that they are doing it.

Most of those who have this cann't stop checking their amp temp... they just cann't ignore which they should.

TL;DR: Don‘t focus in minor issues like the binding post color or whether one input is inverted,

Many were not even aware of it until it was discussed here, and unfortunately cannot be ignored because it is issue until done right.
Its an easy fix, sort of, for those who can realize it and change the connections but not so much for a wider audience.

but on the big picture, a Class D amp that provides the same sound quality as big amps for a fraction of the price.

Absolutely..... with a condition if done right.

 

[SMen]

Happy reading it, but I never thought sound stage has anything or much to do with amplifier.


Most of those who have this cann't stop checking their amp temp... they just cann't ignore which they should.


Many were not even aware of it until it was discussed here, and unfortunately cannot be ignored because it is issue until done right.
Its an easy fix, sort of, for those who can realize it and change the connections but not so much for a wider audience.

Surely it must, if it is more revealing of source than another amplifier, and the source has a sound stage?

I hope you are indeed right about the temperature! I've stopped worrying about mine, running in 30 - 35C ambient they get pretty hot.

 

[Vini darko]

I posed a similar question in the ZA3 thread, but…

Just wanted to report back with something odd. My pair of ZA3s that I gifted to my father after upgrading my chain to V3 Monos, he said the left ZA3 failed first and then the other one eventually went, after he attempted to hook his REL subwoofer up to them via high (speaker) level connection. He is returning the two seemingly dead amplifiers to me to check them out, but they don’t arrive until Monday. For now, he has begun rearranging his chain to utilize the low/line-level input for his subwoofer instead by hooking it up to the second output on his preamp.

Has anyone had an opportunity to or succeed with hooking up a subwoofer via high level connection to a pair of V3 Monos? If so, which wires did you run to which speaker jacks on which channel/amp?

Or is there a technical reason why this is a massive no-no, maybe due to how monoblocs are laid out in general?

-Ed

If the subwoofer high level inputs are common ground and both fosi amp are connected to to sub then yes that would be a problem for a bridged amp. It would short the amps and cause death.

 

[Deleted member 72219]

If the subwoofer high level inputs are common ground and both fosi amp are connected to to sub then yes that would be a problem for a bridged amp. It would short the amps and cause death.

I posted in the ZA3 thread; amps arrived and tested fine. They must’ve simply gone into safe mode.

As a matter of fact, I’ve switched back to the ZA3s myself and will give my dad the V3 Monos instead.

-Ed

 

[Vini darko]

Got a pair with 5A supplies yesterday. Hooked up with rca. Sound is good. Temps are hot but stable at the amps but power supplies are cool.
Used with mission zx2 and monitor audio bronze 500 (both with eq) so far with no issues. Noise at the tweeter seems about the same as my fosi v3. Will try them next with mission m5i wich are a difficult load. The v3 struggled with them quite a bit.

 

[Vini darko]

I posted in the ZA3 thread; amps arrived and tested fine. They must’ve simply gone into safe mode.

-Ed

Gotta love protect circuits glad they are ok

 

[SMen]

I posted in the ZA3 thread; amps arrived and tested fine. They must’ve simply gone into safe mode.

As a matter of fact, I’ve switched back to the ZA3s myself and will give my dad the V3 Monos instead.

-Ed

No way! Why have you gone back to the ZA3's?

Good news about the safe mode ... it might be safe to assume the Monos have a protection circuit also.