Fosi v3 Mono - User Impressions | Owner's Thread

[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.

 

[T&T]

I have no idea if my XLR are inverted or not, but someone should make a video showing what to look for....using Wiim Pro to geshelli akm4499 to fosi mono, Also opamps at position 1 change the sound on XLR, I tried all Muses02 and was fine but I found a combination of all different opamps on all 3 position was absolutely superb.

 

[jbaumann]

Regarding the sound stage in my setup: when measuring the frequency response with REW, the mono blocks had a slightly higher volume starting at 10KHz, and below that at some lower frequencies as well (800Hz, 1.2KHz, 3KHz). Since I have used a DSP to straighten the in-room response, I could without problems do the same with the mono blocks. I assume that with that change the sound stage would be equivalent, and I‘m simply to lazy to do that right now.

Regarding the temperature „problem“ (warning, conjecture): The TPA3255 is designed for a junction temperature of 125°C, which means that if the chip is below 80°C then everything is peachy. And if we now assume a very, very bad heat conduction, then having an enclosure temperature of half that i.e., 40°C would be fine as well. In practice, with the heat sink well connected to the enclosure, we might have 60°C as junction temperature with 40°C. Thus as long as the enclosure is below 70°C I would not worry at all.
And yes, high junction temperatures shorten the life span of everything, but then we are back at my original argument, I‘ll simply buy new ones in 5 years.

 

[EddNog]

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.

I’m not allowed to talk about subjective things around here.

-Ed

 

[Guddu]

I’m not allowed to talk about subjective things around here.

-Ed

Surely you can... this is user impressions and owner's thread

 

[Guddu]

Regarding the sound stage in my setup: when measuring the frequency response with REW, the mono blocks had a slightly higher volume starting at 10KHz, and below that at some lower frequencies as well (800Hz, 1.2KHz, 3KHz). Since I have used a DSP to straighten the in-room response, I could without problems do the same with the mono blocks. I assume that with that change the sound stage would be equivalent, and I‘m simply to lazy to do that right now.

Regarding the temperature „problem“ (warning, conjecture): The TPA3255 is designed for a junction temperature of 125°C, which means that if the chip is below 80°C then everything is peachy. And if we now assume a very, very bad heat conduction, then having an enclosure temperature of half that i.e., 40°C would be fine as well. In practice, with the heat sink well connected to the enclosure, we might have 60°C as junction temperature with 40°C. Thus as long as the enclosure is below 70°C I would not worry at all.
And yes, high junction temperatures shorten the life span of everything, but then we are back at my original argument, I‘ll simply buy new ones in 5 years.

Not bringing up the same discussion again but it's not just about the chip itself. The case isn't just radiating outside, it's radiating inside as well but I am sure you know all that.
Along with that, Mostly it is said in comparision to other amplifiers.
But you can always follow the several posts in this thread or another on this topic if interested..... otherwise its all good.

 

[antcollinet]

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

That is fantastic news - and a good indication of the capability of the protection circuits of these amps.

 

[MCH]

.

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

It is the chip that goes into protection, the Fosi does not have any additional over current protection at the output.

 

[Yeti]

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

Hi , i am Running 2x V3 Mono With 1x Rel T5x no issue
ZA3 might be configured differently since it's a stereo amp to start with
If i dont connect Rel's black wire, i get a hum on the sub
Red wire To + on Right Mono Amp
Black To -- ( either one)
Yello to Left + V3 mono
Have Fosi v3 stereo also but havent tried Rel with it yet

 

[antcollinet]

Hi , i am Running 2x V3 Mono With 1x Rel T5x no issue
ZA3 might be configured differently since it's a stereo amp to start with
If i dont connect Rel's black wire, i get a hum on the sub
Red wire To + on Right Mono Amp
Black To -- ( either one)
Yello to Left + V3 mono
Have Fosi v3 stereo also but havent tried Rel with it yet

This is what REL say in your manual about connecting to a balanced amp like the FOSI:

For differential (i.e. fully balanced) amplifiers using one REL, simply use the standard connecting scheme with the exception of NOT connecting the black wire to a negative speaker terminal. Instead, it should first be allowed to “float” or hang down without connection to ANY terminal. Should hum occur using this method, please try connecting to an unused RCA connector on the rear of a preamp or amplifier. Please contact your dealer should there be any questions concerning this or any other hookup procedure.

By connecting the black wire to your amp black terminal you are short circuiting the amp negative output to ground in the REL sub. This is not going to end well. At best you are over stressing the amp, at worse you might break it.

You should disconnect that now. If you get hum, then as stated you need to connect the black wire to a ground point on your amp such as the ring of an RCA input, or the ground of the balanced connector (depending on what you are using for input)

 

[Yeti]

This is what REL say in your manual about connecting to a balanced amp like the FOSI:



By connecting the black wire to your amp black terminal you are short circuiting the amp negative output to ground in the REL sub. This is not going to end well. At best you are over stressing the amp, at worse you might break it.

You should disconnect that now. If you get hum, then as stated you need to connect the black wire to a ground point on your amp such as the ring of an RCA input, or the ground of the balanced connector (depending on what you are using for input)

yes i have read that
they also are saying that we should not use 1x sub with 2x mono class D amps
and use 2x Rels instead

Anyways thx for the headsup but i am not using V3 monos anymore In My Main Set-up ( where i was testing them )
i Went back with my old equipment

V3 mono are going to be used in Home Theater Only

Cheers

 

[antcollinet]

they also are saying that we should not use 1x sub with 2x mono class D amps
and use 2x Rels instead

I'd tell you that if I were Rel also
I'm not Rel though, so I'll tell you its nonsense as long as you don't connect black wire to black amp terminal, and ensure the two amps have a common ground connection - which they should have from the source.

I'll also tell you - it is much better to use a splitter on the input interconnect to the amp, and drive the sub from the same source as the amp, than to use high level connections.

 

[EddNog]

yes i have read that
they also are saying that we should not use 1x sub with 2x mono class D amps
and use 2x Rels instead

Anyways thx for the headsup but i am not using V3 monos anymore In My Main Set-up ( where i was testing them )
i Went back with my old equipment

V3 mono are going to be used in Home Theater Only

Cheers

Man, they all say that. SVS wanted nothing more than for me to use dual SB-3000s instead of just my one. Double the money for them, double the trouble for me (wife would kill me extra dead!).

-Ed

 

[whit]

For comparison, most Emotiva amps with XLR have had inverted phase (except PA-1, per https://emotivalounge.proboards.com/thread/55385/phase-outs-sources-speakers-important). So going to XLR or RCA there also makes a difference to the output phase. It's never been clear to me whether this is for some technical advantage, or just keeping consistent to a prior standard for the pins.

... Emotiva XPA & DR amps of any generation have their XLR inputs wired with Pin #3+ (the signal’s phase will be reversed by the amp)
... Emotiva PA-1 amps have their XLR outputs wired Pin #2+ (the signal’s phase will not be altered)
...
... ALL Emotiva products are non-inverting through the RCA connections (the signal’s phase will not be altered)

 

[Giro413]

I have two V3 Mono's running my Dali Oberon 5's and to no surprise they do run very hot when ON. However, I am a bit surprised as to how hot they are even in standby mode (Auto). They are about as hot as my Apple TV when it has been running for 30 min. Is that just how it is with these, and is that not using a lot of power for just being idle...

 

[drmevo]

For the phase issue when using RCA, I know I can invert phase on my subwoofer (it has a switch), but I also use an AVR with HT Bypass mode on my preamp for TV/movies/video games. Will the phase inversion actually be noticeable with the surrounds since they're such different signals? I haven't noticed anything so far but I also haven't tested heavily.

 

[Miser_Audioman]

One way to judge the Mono V3s is- did anyone hook them up, dislike them, and put them away/ sell/ return? For me, they beat out an AVR amp, but perhaps that isn’t a huge challenge…

 

[EddNog]

One way to judge the Mono V3s is- did anyone hook them up, dislike them, and put them away/ sell/ return? For me, they beat out an AVR amp, but perhaps that isn’t a huge challenge…

No, but I did end up canceling my preorder for a second pair of them.

That being more the fact that my dad did not actually fry his pair of ZA3s, so I no longer need the replacement pair of V3 Monos.

-Ed

 

[Guddu]

One way to judge the Mono V3s is- did anyone hook them up, dislike them, and put them away/ sell/ return? For me, they beat out an AVR amp, but perhaps that isn’t a huge challenge…

Is it a realistic comparision for it? with an AVR?
OTOH, these are probably technically supirior for sure... but they add significant cost if you add them on top of an AVR which has pre-outs.... AVRs with pre-outs aren't cheap as well, specially the ones with decent DAC/pre-out performance and those decent ones have their power amp around the similar performance as their DACs.

 

[Miser_Audioman]

Is it a realistic comparision for it? with an AVR?
OTOH, these are probably technically supirior for sure... but they add significant cost if you add them on top of an AVR which has pre-outs.... AVRs with pre-outs aren't cheap as well, specially the ones with decent DAC/pre-out performance and those decent ones have their power amp around the similar performance as their DACs.

Well, i prefer the monos to the avr amp in this case. Not disconnecting them and no desire to do so. No this is not a great use case, but my HK 230 avr was free.