Fosi v3 Mono - User Impressions | Owner's Thread

[Giro413]

I have now received my Wiim Ultra, which I have hooked up to the V3 Monos. Even without the turntable hooked up at all the V3's keep clicking on and off. Reason why turnable is not hooked up is that my SUPPHON050: SUPRA PHONO cables won't fit in the ULTRA. A bit surprising to me as the Wiim Pro Plus had no issue with those same cables. Guess I have some tweaking of settings and searching for rca adapters to do.

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.

 

[Brian Hall]

Can confirm. New black boxes and two QC stickers = both units are fixed. I opened up both of them.

Mine were purchased from Amazon. Both came in the new boxes. Both have one QC sticker. They sound great and won't be used with another amp, so it doesn't matter.

 

[avdoc]

Can confirm. New black boxes and two QC stickers = both units are fixed. I opened up both of them.

Looks like the early ones came in a generic Fosi box, until the Mono branded boxes arrived.

Mine were ordered mid-July, direct on Fosi Audio website with their 20% discount offer. Arrived, via a UK shipping agent, so no import duties, a month later. Mine were in the newer boxes with two QC stickers. (Both stickers are silver foil, but one looks yellow due to reflection). I can’t know if new boxes and changed phase is directly connected, but knowing production lines I doubt it is exact!


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I ordered around the same time direct from Fosi for 20% off and also have new boxes and 2 QC stickers.

 

[Fahzz]

FYI: Archimago's Musings has a review of these Part 1.

 

[nitpicker1]

I opened my monoblocks for myself and also noticed that the red cable goes to the black output, and the black cable goes to the red output. Does this mean that I have to connect the speaker cables to the monoblocks in reverse? Sorry for the stupid question, but if they both play out of phase, does it make any difference vs when they both play in phase, unless I plug in a subwoofer?

Is this the definitive way of checking if it's a good or "bad" unit? Or may they have crossed polarity elsewhere as well?

I wish the PSA from them was more clear. But if this is the only problem, I have no issue with resoldering the connectors. Kinda weird mistake to do from factory...

My 2 units are still in their packaging from May order as I haven't had time to set them up yet.

 

[whit]

Can confirm. New black boxes and two QC stickers = both units are fixed. I opened up both of them.

Yup. 2 from Amazon, one QC sticker, not fixed. 2 from Fosi, two QC stickers, fixed. Opened all. Those from Fosi were ordered first, delivered last.

One more on order from Fosi since 8/10, not shipped yet. Assuming the two stickers are from the fix, and that in future they'll be wired right the first time, having just one sticker will no longer have that meaning. So I kinda expect that may be a one-sticker unit when it arrives.

 

[whit]

Is this the definitive way of checking if it's a good or "bad" unit? Or may they have crossed polarity elsewhere as well?

I wish the PSA from them was more clear. But if this is the only problem, I have no issue with resoldering the connectors. Kinda weird mistake to do from factory...

The wire and terminal colors match in the unfixed, original version. Cross wiring them is the fix Fosi did. The reversed polarity comes from earlier in the circuit design, so the cross-wiring is re-reversing it.. Longer term, it's quite possible they'll switch which wire coming off the circuit board is which color. Assuming the colors of the connectors on the back stay in the same positions, the other clue is the unfixed version has the wires each going to the connector closest to it. The fixed version has the wires cross inside.

 

[nitpicker1]

Is there a simple way to test polarity on an audio AC signal from the speaker outputs? I feel I want to verify what's actually going on before and after making changes.

 

[Bernard23]

I'm mid process of converting my system from conventional analogue with a streamer as another line in device, to a using an Ultra as a preamp to do DSP on all sources including vinyl, and to manage an active sub. I've just ordered to V3s to pair with the Ultra, and will replace my trusty Yamaha A-S501, as you can't use the Ultra as a preamp into a preamp line in.....
So general questions, anything I need to know about setting it up to avoid clicks, pops etc, and any cooling recommendations (links to heat sinks etc) as mine are going to sit side by side on an old but much loved Sony cassette deck.

 

[gwing]

Is there a simple way to test polarity on an audio AC signal from the speaker outputs? I feel I want to verify what's actually going on before and after making changes.

Yes. Just reverse the +/- connections to one of your speakers and listen. Ideally with the speakers pointing towards each other a metre or so apart from each other and your head in between but you can just try first from your normal listening position and see if you hear a difference.

If the bass you hear reduces then they were correct to start with so put the connection back how it was before.

If the bass increases it was wrong before so leave it as it is now.

For simple stereo use the above is sufficient - no need to modify the amplifiers.

 

[Brian Hall]

I'm mid process of converting my system from conventional analogue with a streamer as another line in device, to a using an Ultra as a preamp to do DSP on all sources including vinyl, and to manage an active sub. I've just ordered to V3s to pair with the Ultra, and will replace my trusty Yamaha A-S501, as you can't use the Ultra as a preamp into a preamp line in.....
So general questions, anything I need to know about setting it up to avoid clicks, pops etc, and any cooling recommendations (links to heat sinks etc) as mine are going to sit side by side on an old but much loved Sony cassette deck.

I added a small desk fan positioned so it is blowing (lowest setting) over both of them. They got pretty hot without the fan. With the fan they are barely warm to the touch.

Both the v3s and the fan easily fit behind my monitor. Haven't had any issues with pops.

 

[Bernard23]

Just bought mine from Amazon, so no idea whether they will be in phase or crossed polarity. Will be using with a sub that's fed directly from the Ultra, I guess that's where the 180 degrees phase switch comes in handy

 

[nitpicker1]

Yes. Just reverse the +/- connections to one of your speakers and listen. Ideally with the speakers pointing towards each other a metre or so apart from each other and your head in between but you can just try first from your normal listening position and see if you hear a difference.

If the bass you hear reduces then they were correct to start with so put the connection back how it was before.

If the bass increases it was wrong before so leave it as it is now.

For simple stereo use the above is sufficient - no need to modify the amplifiers.

Instead of listening for phase cancellation and guessing, I was thinking along the lines of perhaps finding a playable tone that has a preference of staying positive or negative. Then play this on my current AVR, and compare it with the mono blocks via oscilloscope and be able to confirm correct phase for sure.

 

[gwing]

Instead of listening for phase cancellation and guessing, I was thinking along the lines of perhaps finding a playable tone that has a preference of staying positive or negative. Then play this on my current AVR, and compare it with the mono blocks via oscilloscope and be able to confirm correct phase for sure.

You did ask for a *simple* test

Personally I can't distinguish between music played back in absolute phase or reversed phase even in a sighted test let alone blind so I'm not concerned about whether absolute phase is preserved only that my audio channels match each other. If you do have an, ideally multiple channel, oscilloscope available though that would be interesting and a definitive test although the simple test I suggest is itself accurate enough to avoid the need for any guessing.

 

[antcollinet]

Yes. Just reverse the +/- connections to one of your speakers and listen. Ideally with the speakers pointing towards each other a metre or so apart from each other and your head in between but you can just try first from your normal listening position and see if you hear a difference.

If the bass you hear reduces then they were correct to start with so put the connection back how it was before.

If the bass increases it was wrong before so leave it as it is now.

For simple stereo use the above is sufficient - no need to modify the amplifiers.

I don't think that is going to work. Whatever the polarity of the amp (normal or inverted), you are putting the speakers out of phase with respect to each other. It will only cause a destruction of the sound - especially bass.

Both out of phase sounds fine if not playing with another speaker that is not out of phase.

The only reliable way to measure for this is to look at the waveform of the input compared with the output using an oscilloscope or similar

 

[early rejecter]

and will replace my trusty Yamaha A-S501, as you can't use the Ultra as a preamp into a preamp line in.....

I probably would’ve done the same thing just for simplicity’s sake, but why couldn’t the Ultra have been used as an input for all of your components into the Yamaha integrated?

 

[Nopiano]

I was surprised to discover this morning that my pair of Monos were quite warm while sitting in Auto Off mode, how they’d been overnight. In fact a similar warmth to my Linn Akurate DSM streamer-preamp. The Linn consumes 20 watts on standby, according to Linn’s own spec.

I duly took the temperature of the Monos and they were 29C in an ambient 22C living room. The Linn was a degree cooler, but essentially the same. It seems the stand-by mode isn’t very Eco after all, though maybe it makes them better prepared to sound ok from the beginning of a listening session. Has anyone measured the standby consumption?

 

[Bernard23]

I probably would’ve done the same thing just for simplicity’s sake, but why couldn’t the Ultra have been used as an input for all of your components into the Yamaha integrated?

Because the main reason for replacing the pro plus to the Ultra was sub integration. If you run the Ultra as a fixed output device, then it has no advantage over a pro plus, and you can't run the ultra as the master pre-amp into the Yamaha as it doesn't have a pre-out / main in capability. Wiim is about to drop full sub integration into room correction, including latency so it requires Ultra to operate as a pre-amp (master system volume controller) with the sub out.
Basically, I have to run the Ultra as a fixed line output, and in that configuration, the sub output from the Ultra is fixed, so obviously won't match the mains that are driven by the Yamaha. I can use Ultra with the sub management defeated, but then that is what the pro plus already does.

 

[Guddu]

Has anyone measured the standby consumption?

it’s captured in the first post of this thread.

 

[Miley_B]

Is there a simple way to test polarity on an audio AC signal from the speaker outputs? I feel I want to verify what's actually going on before and after making changes.

I think this has to be the simplest surely?...
Download and play one of these files and watch the driver move. Start off at a moderate level, we don't want to over excurt a driver and don't blame me for any damage! Clearly this won't work with a driver with a High pass filter, ie. a mid woofer or a tweeter.
This will only show the system polarity not the amplifier in isolation.
There are much better ways but they involve test equipment or mics and software such as REW.
Bear in mind that just because the polarity is matched between a full range speaker and a sub it doesn't mean they are phase and time aligned to each other.