Fosi v3 Mono - User Impressions | Owner's Thread

[jboyer]

It does. But none of predetermined choices seem to help.

After much ado and figuring out the potential issues, I noticed that the WiiM Room EQ is (very) sensitive to the volume level selected when doing the EQ.
The Fosi are more sensitive at their lowest RCA input than the NAD is at 0 db. My mistake.

I set the EQ app at a higher volume, and everything sounds GREAT.

The other non-issue: these amplifiers LOVE being pushed. But I live in an apartment, and I have a narrow window of LOUD enjoyment.

I started with Macintosh in the late 60's -- their low end. 60 pounds and their price in gold. Driving Advents. As my earing deteriorated, the 5-pound Fosis priced below a pair of Monster Cables, driving run of the mill Fluance speakers sound as great as the 60's set up. Of course, I am sarcastic. I believe the Class D amplifiers have reached a price/quality point that will have them dominate the bulk of the mid to hi sound market. Was the NAD 3045 to Fosi an upgrade? A tough call. But the WiiM Ultra combination is less money that the NAD. And to me sounds better. Five years -- a long time in electronics.

Thanks for helping.

 

[jeffaegrim]

As @EddNog says , the capitalisation of nearly every word is very jarring to try and read .

Apologies , I assumed some software had been used and added all the capital letters as your other posts didn't look like that .

By all means post a link if youve posted it elsewhere.

I found that whole exchange very amusing but I have to agree, capitalising every word in English in such a large body of text evokes feelings of unease that go beyond the fact that it’s simply grammatically wrong. I was sure that some sort of speech-to-text software was used at first. Glad everything got cleared up)

 

[amix]

Oh, oh. Just had to realize, that my two Kickstarter monos, both with their own 10A PSU, switch to full power from the auto-"standby" mode, when I switch on the RC controlled AC plug, that hosts a lamp here. Same circuit, but outlets on opposite walls.

Doesn't give me much confidence in the AC protection/filtering. @Fosi Audio

 

[burkm]

Suprise ? The Monos are probably triggered by some (unwanted) noise spike or hypersonic "event" on the power line, which appears waekened on the power supplies outgoing (to the amps) DC line. There is a controvery about the efficency of the trigger events for these, because, if they are as sensitive as they are right now they trigger most of the time correctly, if not, they normally trigger to late or at least delayed. A problem, which is hard to solve with such a rather simple circuit...
One does not know, if a different SMPS power "brick" might solve this problem...
Switching to a different phase or circuit might resolve the experienced problems...

As an alternative You could install a simple (and cheap) power grid filter in front of the Fosi Audio power brick, just to test, if this remedies the stated problem...

 

[Rafaille]

I have more than a dozen electronic devices plugged on the same outlet as the amps and many many more on the same electric circuit, plus lamps, smart switches and what not, as I imagine is a common domestic situation.
I have never witnessed the amps turning automatically on when I turned on anything else in my house.
But in my case, I use balanced connections. Would noise picked up by single ended cables be an easier explanation to what seem to be a problem shared by other people - all of those? - using RCA cables?

Edit: Alternatively, a defective amp?

 

[Sokel]

Suprise ? The Monos are probably triggered by some (unwanted) noise spike or hypersonic "event" on the power line, which appears waekened on the power supplies outgoing (to the amps) DC line. There is a controvery about the efficency of the trigger events for these, because, if they are as sensitive as they are right now they trigger most of the time correctly, if not, they normally trigger to late or at least delayed. A problem, which is hard to solve with such a rather simple circuit...
One does not know, if a different SMPS power "brick" might solve this problem...
Switching to a different phase or circuit might resolve the experienced problems...

It's not the PS,it's the child diseases first Signal sense circuits had if not lowpassed and a sensible threshold is put.
That's is how is properly done,4-5 years not a single event:

 

[antcollinet]

Would noise picked up by single ended cables be an easier explanation

Almost certainly - and most likely ground noise. This is almost certainly a system issue - not a FOSI issue. (As are all ground noise issues). Although as @Sokel points out, FOSI could improve immunity to such events (at the expense of the amp not turning on as quickly when music starts)

 

[Sokel]

(at the expense of the amp not turning on as quickly when music starts)

Yes,that's true,it takes 0.5-0.7 sec.it's not instant and you can hear the relays.
When daisy-chained with a 300a or 400a,1200a starts first and it takes an additional 0.5 sec for the daughter amp module.
Compromises,as always.

 

[iLoveCats]

Almost certainly - and most likely ground noise. This is almost certainly a system issue - not a FOSI issue. (As are all ground noise issues). Although as @Sokel points out, FOSI could improve immunity to such events (at the expense of the amp not turning on as quickly when music starts)

I'm hooked up balanced. I have a switched outlet for lamps. 1 switch 2 half outlets with the Fosi's and my whole system in the middle of the circuit. One lamp is an incandescent bulb and the other is an LED floor lamp. If I unplug the LED floor lamp and flip the switch and only the incandescent bulb turns on, the amps stay asleep. With the LED floor lamp in the circuit it wakes the amps with the flip of the switch.

 

[antcollinet]

I'm hooked up balanced. I have a switched outlet for lamps. 1 switch 2 half outlets with the Fosi's and my whole system in the middle of the circuit. One lamp is an incandescent bulb and the other is an LED floor lamp. If I unplug the LED floor lamp and flip the switch and only the incandescent bulb turns on, the amps stay asleep. With the LED floor lamp in the circuit it wakes the amps with the flip of the switch.

Try disconnecting the input. If it still powers up from standby when you switch the LED it is definitely mains borne (or possibly - though unlikely) radiated)

If not then it is noise on the input. Which could be a grounding issue, or it could be disturbance caused inside your source.

 

[Sokel]

I'm hooked up balanced. I have a switched outlet for lamps. 1 switch 2 half outlets with the Fosi's and my whole system in the middle of the circuit. One lamp is an incandescent bulb and the other is an LED floor lamp. If I unplug the LED floor lamp and flip the switch and only the incandescent bulb turns on, the amps stay asleep. With the LED floor lamp in the circuit it wakes the amps with the flip of the switch.

Leds can cause mayhem,somewhere in here I posted some quick and dirty measurements to show how much,no matter the gear and no matter if connected,unconnected,unbalanced or balanced.

If at the same electric phase can cause high freq spikes even in other rooms,specially the dim-able ones and it goes without saying that the cheap are the worst.
Someone posted a site that measures leds couple of months ago and it's all there.

I have seen it enough to have a different phase for my gear (same goes for motors of every kind,HVACs,etc )

 

[Petrushka]

Leds can cause mayhem,somewhere in here I posted some quick and dirty measurements to show how much,no matter the gear and no matter if connected,unconnected,unbalanced or balanced.

If at the same electric phase can cause high freq spikes even in other rooms,specially the dim-able ones and it goes without saying that the cheap are the worst.
Someone posted a site that measures leds couple of months ago and it's all there.

I have seen it enough to have a different phase for my gear (same goes for motors of every kind,HVACs,etc )

Phillips.

LEDs.

 

[amix]

Would noise picked up by single ended cables be an easier explanation to what seem to be a problem shared by other people - all of those? - using RCA cables?

Very interesting! Indeed I have the RCA cables in use. Since I got no means to test XLR I can't comment on this any further.

 

[amix]

I [...] have a different phase for my gear

How does one implement this? Do you run more wires to your house?

 

[Unbalanced]

I have more than a dozen electronic devices plugged on the same outlet as the amps and many many more on the same electric circuit, plus lamps, smart switches and what not, as I imagine is a common domestic situation.
I have never witnessed the amps turning automatically on when I turned on anything else in my house.
But in my case, I use balanced connections. Would noise picked up by single ended cables be an easier explanation to what seem to be a problem shared by other people - all of those? - using RCA cables?

Edit: Alternatively, a defective amp?

My pair of Monos have been in operation for about a month. I am using RCA inputs. I have not had problems with the units coming out of standby. I did have a problem with a unit not going into standby and after replacing that one everything has been good. That said I have read reports from others about the units randomly coming out of standby. I get the impression that the standby circuit is not as robust as it should be with issues in both directions.

 

[Sokel]

How does one implement this? Do you run more wires to your house?

It's a choice you make when you install your electrical grid in your house.
You can either have one-phase or three phase.I chose the later right from the start as I built it fairly recently and I use one of these for my gear only.

 

[Rafaille]

My pair of Monos have been in operation for about a month. I am using RCA inputs. I have not had problems with the units coming out of standby. I did have a problem with a unit not going into standby and after replacing that one everything has been good. That said I have read reports from others about the units randomly coming out of standby. I get the impression that the standby circuit is not as robust as it should be with issues in both directions.

Your former unit appears to be faulty indeed but for those whose units come out of standby without music being played, the simple explanation of picking up noise (through either unbalanced input or power line) still stands.

 

[Rafaille]

Phillips.

LEDs.

Glass half empty
Damn Fosi, the threshold on your auto-on feature is way too sensitive, when I turn on my LED it turns on as well

Glass half full
Thank you Fosi, the trigger on your auto-on feature made me realise that my LED is polluting my electrical circuit with noise

 

[Blew]

It's a choice you make when you install your electrical grid in your house.
You can either have one-phase or three phase.I chose the later right from the start as I built it fairly recently and I use one of these for my gear only.

How can you tell which phase a circuit uses in a house that has a three-phase power supply? In my case we have large old aircon units on separate circuits, and multiple GPO circuits in the house. I'm in Australia which is 240v if that makes a difference.

 

[Sokel]

How can you tell which phase a circuit uses in a house that has a three-phase power supply? In my case we have large old aircon units on separate circuits, and multiple GPO circuits in the house. I'm in Australia which is 240v if that makes a difference.

You can't unless you built it this way right from the beginning.
It's one thing to have separate circuits and another to have completely separate lines you can distribute coming in the house.
I'm in Europe,we have 230V here,we too have large HVAC and stuff at the own circuits but at the same phase.