Fosi v3 Mono - User Impressions | Owner's Thread

[Unbalanced]

UPDATE: It seems that setting the gain of my Fosi V3 Monos to 25db instead of 31 makes them not turn on at random as they did before. At least they no longer do after having switched the gain settings on them. Still hooked up to my WiiM ULTRA.

I have a similar setup. Two V3 Monos fed from a WiiM Pro Plus using the RCA cable that came with the WiiM. Two separate 48V 5A power supplies. Gain on the Monos is set to 25db. All items received this past Sunday from Amazon Canada. Both units packaged in fancy printed box.

Everything works great and sounds great with the exception that one of the Monos does not enter standby. I tried reversing the RCA inputs. Same unit does not enter standby. I tried side by side placement and reverse stack order. Same unit does not enter standby.

I contacted Fosi. They asked me to disconnect the inputs and then power up the Monos to auto. They should enter standby after 20 seconds which they both do. Fosi told me to get better RCA cables.

Final test that I did was to play music and then disconnect the RCA input from the offending unit. The unit does not enter standby after 10 minutes, 20 minutes ...

I have ordered a replacement from Amazon and will be returning the offending unit.

 

[antcollinet]

Thanks so much, I’d completely overlooked that! It also coincides with my estimate. In the EU I thought all standby settings had to be 0.5 watts or lower

It's not a standby setting. Although fosi do call it that. It is obviously just a lower power mode.

The EU regs apply to an On/Off control (typically on a remote control) which doesn't remove power completely from a device (so it can still power back on from the remote) The only on/off control on the FOSI is the switch.

 

[MCH]

It's not a standby setting. Although fosi do call it that. It is obviously just a lower power mode.

The EU regs apply to an On/Off control (typically on a remote control) which doesn't remove power completely from a device (so it can still power back on from the remote) The only on/off control on the FOSI is the switch.

Yes, but the rule says such devices must have such stand by mode, which the fosi obviously don't have -> it doesn't comply.
Yes, I know you were not saying it does comply, just to complete the -valuable imo- information

 

[nitpicker1]

@nitpicker1
Would surpise me, because Fosi Audio didn't announce any significant changes, just the official message, that inverting amps have 1 QC whilst non-inverting amps have 2 of those (see foto of the Fosi Audio Service department).
All V3 mono, which have been bought from Fosi Audio partners (Amazon, Ebay etc.), haven't been converted yet to my knowledge, because of existing inventory as far as I know. New shipments might be available soon...

If Your V3 mono amps carry 1 QC sticker they should still be of the inverting type, as long as they weren't shipped from Fosi Audio directly beginning with August 2nd 2024.
All partners to my knowledge are delivering still the "old" inverting version.
PCB version: The PCB should carry the imprint 03/28/2024 (?) if the PCB had not been modified yet...
Your amps should thus (probably) be of the inverting type...
Are You sure that isn't the case here... ???

Note: Looking at Your photos I am identifying a PCB version dated December 28th 2023. At that time there wasn't even known to Fosi Audio, that the V3 mono was inverting the signal... so Your conclusion might be erroneous ...

There are 2 dates. One on the mounted mini boards, and one on the main. Both are same batch march 24. I've contacted fosi about this as well, as I'm confused about my results.

 

[antcollinet]

Yes, but the rule says such devices must have such stand by mode, which the fosi obviously don't have -> it doesn't comply.
Yes, I know you were not saying it does comply, just to complete the -valuable imo- information

I've had a look and can't find such a universal requirement. I have found a get out clause where if such a mode were not appropriate for intended use it can be omitted. And obviously it is not required for all equipment.

EG

My turntable has no standby mode. It simply has a switch that turns the motor on or off. Same for my kettle, toaster, and any number of electrical items. My sub has no standby mode either - just a power switch.


EDIT:
Reg is here - section 2 of the ecodesegn requirements don't require a stand by mode, but do seem to required a power management function that will put the device into standby or off modes after a period of time. I assume the products mentioned above (especially turntable and sub) are either out of scope - or are claiming inappropriateness. Or are simply not compliant.

L_2023103EN.01002901.xml

 

[nitpicker1]

Unlikely to work due to the inevitable delays between audacity - and the output in analogue form. Probably longer than a full cycle at 20Hz.

But if you have an oscilloscope, put one channel on the analogue input to the amp, and the other on the speaker output. Job done.

Audacity was mainly a way to get an idea of the input sine, and with a slow wave like that, You can definitely see it near realtime. Both on scope and visually on drivers.

Seemed fine to me, but everything else tells me I have inverted units. Gonna try with umik/rew also later today if I get some spare time.

 

[MCH]

I've had a look and can't find such a universal requirement. I have found a get out clause where if such a mode were not appropriate for intended use it can be omitted. And obviously it is not required for all equipment.

EG

My turntable has no standby mode. It simply has a switch that turns the motor on or off. Same for my kettle, toaster, and any number of electrical items. My sub has no standby mode either - just a power switch.


EDIT:
Reg is here - section 2 of the ecodesegn requirements don't require a stand by mode, but do seem to required a power management function that will put the device into standby or off modes after a period of time. I assume the products mentioned above (especially turntable and sub) are either out of scope - or are claiming inappropriateness. Or are simply not compliant.

L_2023103EN.01002901.xml

Standby, networked standby and Off mode

Off mode, standby and networked standby mode. Energy efficiency of products.

energy-efficient-products.ec.europa.eu

 

[Sokel]

I've had a look and can't find such a universal requirement. I have found a get out clause where if such a mode were not appropriate for intended use it can be omitted. And obviously it is not required for all equipment.

EG

My turntable has no standby mode. It simply has a switch that turns the motor on or off. Same for my kettle, toaster, and any number of electrical items. My sub has no standby mode either - just a power switch.


EDIT:
Reg is here - section 2 of the ecodesegn requirements don't require a stand by mode, but do seem to required a power management function that will put the device into standby or off modes after a period of time. I assume the products mentioned above (especially turntable and sub) are either out of scope - or are claiming inappropriateness. Or are simply not compliant.

L_2023103EN.01002901.xml

Here's the rule:

Standby, networked standby and Off mode

Off mode, standby and networked standby mode. Energy efficiency of products.

energy-efficient-products.ec.europa.eu

• from 2025, devices must not consume more than 0.5 Watts in standby or in off mode, or 0.8 Watt if they are on standby while displaying their status or information
• from 2027, devices must not consume more than 0.5 Watts in standby, 0.3 Watts in off mode, or 0.8 Watts if they are on standby while displaying their status or information
• From 2027, devices in networked standby must not consume more than 2 to 7 Watts depending on the product

 

[antcollinet]

Audacity was mainly a way to get an idea of the input sine, and with a slow wave like that, You can definitely see it near realtime. Both on scope and visually on drivers.

Seemed fine to me, but everything else tells me I have inverted units. Gonna try with umik/rew also later today if I get some spare time.

But if you have only 25ms delay between Audacity, and output from the DAC, that will be enough to apparently fully invert the phase of a 20hz sine. Only 12ms to make the result indeterminate (90 degree phase shift). And obviously much smaller delays for higher frequencies. Unless you know the delay time of all the buffers in your computer and DAC, then you can only trust the result if you are measuring actual input to the amp - not the graphical representation in Audacity.

 

[antcollinet]

Standby, networked standby and Off mode

Off mode, standby and networked standby mode. Energy efficiency of products.

energy-efficient-products.ec.europa.eu

View attachment 389153

I saw that - but the "equipment can" have these modes suggested they were not mandatory. which then means the clause you highlight would not apply to those devices which didn't have the modes.

However, see my later edit to my post above. Looking at the actual regulation does suggest it is mandatory to have power management to switch off.

 

[MCH]

I saw that - but the "equipment can" have these modes suggested they were not mandatory. which then means the clause you highlight would not apply to those devices which didn't have the modes.

However, see my later edit to my post above. Looking at the actual regulation does suggest it is mandatory to have power management to switch off.

It is not only that most classes of devices must have either OFF or standby mode, it is also, and here is where all these amps fail, they must enter those modes automatically.
See the section 2.2 of the guidelines document linked in the link I posted before.

(Some of the devices you mentioned before have specific rules)

 

[burkm]

There are 2 dates. One on the mounted mini boards, and one on the main. Both are same batch march 24. I've contacted fosi about this as well, as I'm confused about my results.

I may stand corrected but the version print - as visible (Main-PCB) - on 2nd photo shows a date "March 28th 2024" (sorry about the other wrong date).
This is the same date as shown on my PCBs too. All 5 of them are still inverting the phase, and I switched around the speaker connections to compensate for the phase reversal.
Thus your amps are probably inverting the phase too, which the one QC sticker also suggests.

 

[Sokel]

It is not only that most classes of devices must have either OFF or standby mode, it is also, and here is where all these amps fail, they must enter those modes automatically.
See the section 2.2 of the guidelines document linked in the link I posted before.

(Some of the devices you mentioned before have specific rules)

If reports here are true and the power numbers with the amps just connected to the bricks and in an off state consuming 10W each the problem is not the amps,it's the bricks.
It's there that these modes should be applied.And there's not a way to cut corners as they don't even have a kill switch.

If I'm wrong about it,users please correct me.

 

[nitpicker1]

But if you have only 25ms delay between Audacity, and output from the DAC, that will be enough to apparently fully invert the phase of a 20hz sine. Only 12ms to make the result indeterminate (90 degree phase shift). And obviously much smaller delays for higher frequencies. Unless you know the delay time of all the buffers in your computer and DAC, then you can only trust the result if you are measuring actual input to the amp - not the graphical representation in Audacity.

Had not considered this, it could explain things. Will redo things by measuring actual input. Thank you.

 

[MCH]

If reports here are true and the power numbers with the amps just connected to the bricks and in an off state consuming 10W each the problem is not the amps,it's the bricks.
It's there that these modes should be applied.And there's not a way to cut corners as they don't even have a kill switch.

If I'm wrong about it,users please correct me.

The bricks are also covered, by a different regulation

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32019R1782

I didn't read it but seems that for PSU the requirements are about power consumption in "no load condition" (anex II)

 

[Sokel]

The bricks are also covered, by a different regulation

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32019R1782

I didn't read it but seems that for PSU the requirements are about power consumption in "no load condition" (anex II)

This one?



If that's the case the 0.21W or 0.3W consumption rule is even lower than the 0.5W rule.
It's not clear to me though if the "no load" condition means with the following device at off state or no device at all connected.
Cause even if off any device can present some load.

 

[Nopiano]

The bricks are also covered, by a different regulation

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32019R1782

I didn't read it but seems that for PSU the requirements are about power consumption in "no load condition" (anex II)

This is fascinating, because the same ‘brick’ powering the v3 stereo consumes next to nothing and the amp doesn’t stay warm, presumably because off is fully off. The Monos shouldn’t need 10watts each just to service the Auto on/off function should they?

Maybe I should only use Auto during the day, but shut down fully overnight. That’s what I do with my other power amps, but they didn’t have auto sensing.

 

[MCH]

This is fascinating, because the same ‘brick’ powering the v3 stereo consumes next to nothing and the amp doesn’t stay warm, presumably because off is fully off. The Monos shouldn’t need 10watts each just to service the Auto on/off function should they?

Maybe I should only use Auto during the day, but shut down fully overnight. That’s what I do with my other power amps, but they didn’t have auto sensing.

Audio sense is a great feature, but in the case of the v3 monos the power consumption in stand by is so high, that it doesn't make sense, and what is more, it can be misleading for users that think they are using next to nothing and leave them 24/7
My boxem amp has audio sense with power <0.5w in stand by, so it must be doable.

 

[stigger]

If reports here are true and the power numbers with the amps just connected to the bricks and in an off state consuming 10W each the problem is not the amps,it's the bricks.
It's there that these modes should be applied.And there's not a way to cut corners as they don't even have a kill switch.

If I'm wrong about it,users please correct me.

My amp arrived a couple of days ago, so I tried powering it through a lab supply. On - 5.2W, Auto - 3W, Off - 0W. So indeed, when it's off, it's off, and the rest is the PSU idle consumption. The amp's auto mode still consumes way too much, though. So my point stands: the "idling" module in the amp has no excuse for consuming 3 watts, that's bad design. That's almost 8 euros per year in some countries, if I'm not mistaken.

 

[Sokel]

@stigger
Did you run any measurement with the stock brick?
Or you didn't get any of them at all?