Fosi v3 Mono - User Impressions | Owner's Thread

[renoxd]

Makes me wonder if this could be an issue related to my turntable, which is not yet grounded as it is connected directly to the line in port of my WiiM Pro Plus. The WPP does not have a ground input or a phono input. I will ground the turntable, and most likely run it through the phono stage on my WiiM Ultra when that lands on my doorstep.

just unplug all inputs and leave Wiim with wifi connection into your amp .... and let us know hit it behaves

 

[antcollinet]

Makes me wonder if this could be an issue related to my turntable, which is not yet grounded as it is connected directly to the line in port of my WiiM Pro Plus. The WPP does not have a ground input or a phono input. I will ground the turntable, and most likely run it through the phono stage on my WiiM Ultra when that lands on my doorstep.

Does your turntable have a built in phono stage? If not the Wiim Pro Plus analogue input is completely unsuitable for an input directly from the turntable.

 

[amix]

The thought of the amp operating 'normally' at under 85C came as a surprise.

These amps are different to traditional amps. They are more comparable to computer chips. If you look at a typical desktop CPU or GPU, they will typically be in the low 40s (centigrade) when idling, and go 10-20 degrees up when under load. That's how I understand it.

 

[amix]

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...

Search. Read.

 

[amix]

I have two monos with a dedicated 48V/10A supply each. How can I know, how much current goes into the speakers?

 

[Lux_ury]

I have two monos with a dedicated 48V/10A supply each. How can I know, how much current goes into the speakers?

Maybe a clamp meter?

 

[C0mbat]

I received mine today and got them hooked up straight away, set to auto. I ran them for about 30 mins but haven't since then (about 2 hours since). One of them is significantly hotter than the other one. I'm wondering whether the auto stand by has kicked in on one of them but not the other one? How can I tell if they are in stand by?

I've got a major concern if one of them is always going to be hotter than the other. I've swapped out my Aiyima A03 Max (I ran those in mono to) and they didn't get as hot as the hottest one is. The heat is particularly concerning given that I've not actually feeding either of them a signal.

Unlike @T&T, I've not rolled any op amps. I just plugged and played.

Ok. So the issue is not that one is hotter than the other. The issue is with the Auto On/Stand By (like many others here). I'm using a WiiM Pro Plus but feeding the signal to my Kef KC62 Sub and then using the Kef's high pass filter to feed the Fosi Audio V3 Mono's. I've not done full testing but at minimum, the Fosi's are occasionally picking up a signal from the Kef (I know that as I had the WiiM on standby while still having the Kef on). One of the amps is getting triggered more often than the other and that is why it often feels hotter.

I'm not sure what to do as one of the main reasons for getting the Fosi's was for this auto stand by because my Aiyima 07 Max's were sitting idle but very hot all day long.

I did plan on getting the WiiM Ultra at some point, which would allow me to use it's sub out and then not have the Kef part of the chain to the amp. But the WiiM Ultra seems to be triggering the amps stand by with a lot of other users so far to.

 

[avdoc]

Ok. So the issue is not that one is hotter than the other. The issue is with the Auto On/Stand By (like many others here). I'm using a WiiM Pro Plus but feeding the signal to my Kef KC62 Sub and then using the Kef's high pass filter to feed the Fosi Audio V3 Mono's. I've not done full testing but at minimum, the Fosi's are occasionally picking up a signal from the Kef (I know that as I had the WiiM on standby while still having the Kef on). One of the amps is getting triggered more often than the other and that is why it often feels hotter.

I'm not sure what to do as one of the main reasons for getting the Fosi's was for this auto stand by because my Aiyima 07 Max's were sitting idle but very hot all day long.

I did plan on getting the WiiM Ultra at some point, which would allow me to use it's sub out and then not have the Kef part of the chain to the amp. But the WiiM Ultra seems to be triggering the amps stand by with a lot of other users so far to.

Numerous people have reported issues with the V3Ms activating without a signal. If that's a deal-breaker for you, I think you're going to have to find a different amp. The V3Ms use a huge amount of power in "stand-by" mode. If you can't turn them on and off manually, I'd look elsewhere.

 

[EddNog]

Is it really that big a deal? A lot of people still listen to CDs or vinyl (not I), and there’s the whole ritual then of putting the disc or album onto the transport before playing. It’s just part of the listening process. Is it that much to turn amps on and then off when you’re done to close up your listening session? Maybe I’m just crazy to treat it, literally, as part of a ritual component of the listening experience. ¯\_(ツ)_/¯

-Ed

 

[C0mbat]

Is it really that big a deal? A lot of people still listen to CDs or vinyl (not I), and there’s the whole ritual then of putting the disc or album onto the transport before playing. It’s just part of the listening process. Is it that much to turn amps on and then off when you’re done to close up your listening session? Maybe I’m just crazy to treat it, literally, as part of a ritual component of the listening experience. ¯\_(ツ)_/¯

-Ed

I get that it's not a big deal for everyone. But I wasn't suggesting that everyone return their amps. For me? I've not got CDs or Vinyl. Everyone situation/set up/environment is different. I work from home in a dedicated office and switch music on and off constantly through the day in between meetings and other things. Yes, I can get up to switch them on and off each time but I actually think that would result in me listening to less music. So isn't that defeating the purpose for my particular use case? I actually have them plugged in to smart plugs so I could even switch them on and off via that each time. But that just adds further steps to the workflow.

I wasn't really expecting any musical change with the Fosi's vs the Aiyima and as far as I can tell, that is the case. They sound the same. So the misbehaving auto on/stand by is more of a pain to me than it likely is to others. But I feel that I have a right to be disappointed given that it was a clearly defined value proposition that Fosi marketed.

 

[C0mbat]

Numerous people have reported issues with the V3Ms activating without a signal. If that's a deal-breaker for you, I think you're going to have to find a different amp. The V3Ms use a huge amount of power in "stand-by" mode. If you can't turn them on and off manually, I'd look elsewhere.

When you say a huge amount of power in stand by is it really? They are hot to touch when on but almost cool to touch in stand by. To be honest, I don't really care about the power usage. I wanted them to be cool when not in use because I'm in a small room and during the summary months the room gets warm enough as it is. I don't want two little radiators on all of the time

 

[SMen]

Numerous people have reported issues with the V3Ms activating without a signal. If that's a deal-breaker for you, I think you're going to have to find a different amp. The V3Ms use a huge amount of power in "stand-by" mode. If you can't turn them on and off manually, I'd look elsewhere.

I am wondering if in fact there might actually be a signal, but we just think there isn't, or hasn't been - but obviously if there are variations in the units being sent out then that would be a problem...

I have mine connected through balanced connection to a switcher between DAC with more than one source, and a phono pre-amp. If there is no signal for 10 or so minutes they definitely de-activate, and re-activate quickly when there is a signal, of if I simply switch sources before any music is played also with the switcher.

Is it really a huge amount of power though, in stand-by? I used to keep a valve pre-amp and class AB on most of the time, back in the day

 

[antcollinet]

I have two monos with a dedicated 48V/10A supply each. How can I know, how much current goes into the speakers?

By measuring it. It will, of course, vary with the volume.

You could get a good estimate by measuring the voltage, which is easier - and assuming the nominal impedance of the speakers.

I = V/R

 

[antcollinet]

Is it that much to turn amps on and then off when you’re done to close up your listening session?

I just yell at Alexa to do it for me.

 

[antcollinet]

I'm using a WiiM Pro Plus but feeding the signal to my Kef KC62 Sub and then using the Kef's high pass filter to feed the Fosi Audio V3 Mono's. I've not done full testing but at minimum, the Fosi's are occasionally picking up a signal from the Kef

That is not an ideal situation for ground noise. You have (presumably) long unbalanced cables from the wiim to the sub, and then additional long cables from the the sub back to the V3's. If there is a ground loop then noise can be induced on both cables (additively) to be input into the V3's auto on circuit.

 

[DavidMcRoy]

Something like this might be a workaround

 

[Rafaille]

Ok. So the issue is not that one is hotter than the other. The issue is with the Auto On/Stand By (like many others here). I'm using a WiiM Pro Plus but feeding the signal to my Kef KC62 Sub and then using the Kef's high pass filter to feed the Fosi Audio V3 Mono's. I've not done full testing but at minimum, the Fosi's are occasionally picking up a signal from the Kef (I know that as I had the WiiM on standby while still having the Kef on). One of the amps is getting triggered more often than the other and that is why it often feels hotter.

I'm not sure what to do as one of the main reasons for getting the Fosi's was for this auto stand by because my Aiyima 07 Max's were sitting idle but very hot all day long.

I did plan on getting the WiiM Ultra at some point, which would allow me to use it's sub out and then not have the Kef part of the chain to the amp. But the WiiM Ultra seems to be triggering the amps stand by with a lot of other users so far to.

Unless your amp is faulty, I think it just points to your sub sending a bit too much noise through and waking up the amp.
Option 1: you don't care about the loss of SNR and you use your smart plug, maybe via an accessible smart switch on your office desk?
Option 2: you eliminate that noise by not using the sub as an interconnect and invest in another streamer/preamp that does high pass filtering. Personally I would recommend a DSP 'box' like a single board computer running CamillaDSP coupled to an audio interface of some kind. Going the extra mile: use an audio interface with balanced outputs to eliminate any possibility of EMI.
Edit: @antcollinet beat me to it

 

[Rafaille]

That is not an ideal situation for ground noise.

I would rather say that it IS an ideal situation for ground noise

 

[C0mbat]

That is not an ideal situation for ground noise. You have (presumably) long unbalanced cables from the wiim to the sub, and then additional long cables from the the sub back to the V3's. If there is a ground loop then noise can be induced on both cables (additively) to be input into the V3's auto on circuit.

I'm in a fairly small room so the cable lengths aren't too bad. I think they are 2m RCAs from the WiiM to the sub and 2m RCAs from the sub to the Fosi's. Is that likely to cause issues?

 

[C0mbat]

Unless your amp is faulty, I think it just points to your sub sending a bit too much noise through and waking up the amp.
Option 1: you don't care about the loss of SNR and you use your smart plug, maybe via an accessible smart switch on your office desk?
Option 2: you eliminate that noise by not using the sub as an interconnect and invest in another streamer/preamp that does high pass filtering. Personally I would recommend a DSP 'box' like a single board computer running CamillaDSP coupled to an audio interface of some kind. Going the extra mile: use an audio interface with balanced outputs to eliminate any possibility of EMI.
Edit: @antcollinet beat me to it

Thanks for your responses @Rafaille and @antcollinet - Interestingly I swapped over the left and right channel RCA cables in to the Fosi's last night and the auto on/stand by is working much better so far today. There hasn't been any ghost signals that have triggered either amps to come on. Yesterday both were being triggered but one was being triggered far more frequently.

It means that I'm now getting stereo in reverse but given that there's no corresponding image from a TV it's not an issue

I'll keep monitoring but when I change my WiiM Pro Plus to the Ultra, I'll be able to use the sub out and that will remove the sub from the chain in to the amps, further reducing the risk of them being being triggered on.

Edit: Since stopping listening to music 30 mins ago I've watched as one amp went in to stand by after 10 mins and the second one took 30 mins. Then within 10 seconds of the second one going in to stand by both were bizarrely triggered to come back on. So my issue isn't resolved. I might take the sub out of the chain and see if it's better with just the WiiM feeding the amps.